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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<HTML
><HEAD
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>Administering Client Machines and the Cache Manager</TITLE
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>AFS Administration Guide: Version 3.6</TH
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><DIV
CLASS="chapter"
><H1
><A
NAME="HDRWQ387"
></A
>Chapter 10. Administering Client Machines and the Cache Manager</H1
><P
>This chapter describes how to administer an AFS client machine, which is any machine from which users can access the AFS
filespace and communicate with AFS server processes. (A client machine can simultaneously function as an AFS server machine if
appropriately configured.) An AFS client machine has the following characteristics: <UL
><LI
><P
>The kernel includes the set of modifications, commonly referred to as the <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>Cache Manager</I
></SPAN
>, that
enable access to AFS files and directories. You can configure many of the Cache Manager's features to suit your users'
needs. See <A
HREF="c21473.html#HDRWQ390"
>Overview of Cache Manager Customization</A
>.</P
></LI
><LI
><P
>The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc</B
></SPAN
> directory on the local disk stores several configuration files. See
<A
HREF="c21473.html#HDRWQ392"
>Configuration Files in the /usr/vice/etc Directory</A
>.</P
></LI
><LI
><P
>A cache stores temporary copies of data fetched from AFS file server machines, either in machine memory or on a
devoted local disk partition. See <A
HREF="c21473.html#HDRWQ394"
>Determining the Cache Type, Size, and Location</A
> and <A
HREF="c21473.html#HDRWQ402"
>Setting Other Cache Parameters with the afsd program</A
>.</P
></LI
></UL
></P
><P
>To learn how to install the client functionality on a machine, see the <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>IBM AFS Quick Beginnings</I
></SPAN
>.</P
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="HDRWQ388"
>Summary of Instructions</A
></H1
><P
>This chapter explains how to perform the following tasks by using the indicated commands:</P
><DIV
CLASS="informaltable"
><A
NAME="AEN21494"
></A
><TABLE
BORDER="0"
FRAME="void"
CLASS="CALSTABLE"
><COL
WIDTH="67*"><COL
WIDTH="33*"><TBODY
><TR
><TD
>Display cache size set at reboot</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cat /usr/vice/etc/cacheinfo</B
></SPAN
></TD
></TR
><TR
><TD
>Display current cache size and usage</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getcacheparms</B
></SPAN
></TD
></TR
><TR
><TD
>Change disk cache size without rebooting</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setcachesize</B
></SPAN
></TD
></TR
><TR
><TD
>Initialize Cache Manager</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
></TD
></TR
><TR
><TD
>Display contents of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cat /usr/vice/etc/CellServDB</B
></SPAN
></TD
></TR
><TR
><TD
>Display list of database server machines from kernel memory</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs listcells</B
></SPAN
></TD
></TR
><TR
><TD
>Change list of database server machines in kernel memory</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs newcell</B
></SPAN
></TD
></TR
><TR
><TD
>Check cell's status regarding setuid</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getcellstatus</B
></SPAN
></TD
></TR
><TR
><TD
>Set cell's status regarding setuid</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setcell</B
></SPAN
></TD
></TR
><TR
><TD
>Set server probe interval</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs checkservers -interval</B
></SPAN
></TD
></TR
><TR
><TD
>Display machine's cell membership</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cat /usr/vice/etc/ThisCell</B
></SPAN
></TD
></TR
><TR
><TD
>Change machine's cell membership</TD
><TD
>Edit <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/ThisCell</B
></SPAN
></TD
></TR
><TR
><TD
>Flush cached file/directory</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs flush</B
></SPAN
></TD
></TR
><TR
><TD
>Flush everything cached from a volume</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs flushvolume</B
></SPAN
></TD
></TR
><TR
><TD
>Update volume-to-mount-point mappings</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs checkvolumes</B
></SPAN
></TD
></TR
><TR
><TD
>Display Cache Manager's server preference ranks</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getserverprefs</B
></SPAN
></TD
></TR
><TR
><TD
>Set Cache Manager's server preference ranks</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setserverprefs</B
></SPAN
></TD
></TR
><TR
><TD
>Display client machine addresses to register</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getclientaddrs</B
></SPAN
></TD
></TR
><TR
><TD
>Set client machine addresses to register</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setclientaddrs</B
></SPAN
></TD
></TR
><TR
><TD
>Control the display of warning and status messages</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs messages</B
></SPAN
></TD
></TR
><TR
><TD
>Display and change machine's system type</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs sysname</B
></SPAN
></TD
></TR
><TR
><TD
>Enable asynchronous writes</TD
><TD
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs storebehind</B
></SPAN
></TD
></TR
></TBODY
></TABLE
></DIV
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="HDRWQ390"
>Overview of Cache Manager Customization</A
></H1
><P
>An AFS client machine's kernel includes a set of modifications, commonly referred to as the <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>Cache
Manager</I
></SPAN
>, that enable access to AFS files and directories and communications with AFS server processes. It is common
to speak of the Cache Manager as a process or program, and in regular usage it appears to function like one. When configuring
it, though, it is helpful to keep in mind that this usage is not strictly accurate.</P
><P
>The Cache Manager mainly fetches files on behalf of application programs running on the machine. When an application
requests an AFS file, the Cache Manager contacts the Volume Location (VL) Server to obtain a list of the file server machines
that house the volume containing the file. The Cache Manager then translates the application program's system call requests into
remote procedure calls (RPCs) to the File Server running on the appropriate machine. When the File Server delivers the file, the
Cache Manager stores it in a local <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>cache</I
></SPAN
> before delivering it to the application program.</P
><P
>The File Server delivers a data structure called a <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>callback</I
></SPAN
> along with the file. (To be precise, it
delivers a callback for each file fetched from a read/write volume, and a single callback for all data fetched from a read-only
volume.) A valid callback indicates that the Cache Manager's cached copy of a file matches the central copy maintained by the
File Server. If an application on another AFS client machine changes the central copy, the File Server breaks the callback, and
the Cache Manager must retrieve the new version when an application program on its machine next requests data from the file. As
long as the callback is unbroken, however, the Cache Manager can continue to provide the cached version of the file to
applications on its machine, which eliminates unnecessary network traffic.</P
><P
>The indicated sections of this chapter explain how to configure and customize the following Cache Manager features. All
but the first (choosing disk or memory cache) are optional, because AFS sets suitable defaults for them. <UL
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>disk or memory cache</I
></SPAN
>. The AFS Cache Manager can use machine memory for caching instead of space
on the local disk. Deciding which to use is the most basic configuration decision you must make. See <A
HREF="c21473.html#HDRWQ394"
>Determining the Cache Type, Size, and Location</A
>.</P
></LI
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>cache size</I
></SPAN
>. Cache size probably has the most direct influence on client machine performance. It
determines how often the Cache Manager must contact the File Server across the network or discard cached data to make room
for newly requested files, both of which affect how quickly the Cache Manager delivers files to users. See <A
HREF="c21473.html#HDRWQ394"
>Determining the Cache Type, Size, and Location</A
>.</P
></LI
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>cache location</I
></SPAN
>. For a disk cache, you can alter the conventional cache directory location
(<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/cache</B
></SPAN
>) to take advantage of greater space availability on other disks on the
machine. A larger cache can result in faster file delivery. See <A
HREF="c21473.html#HDRWQ394"
>Determining the Cache Type, Size,
and Location</A
>.</P
></LI
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>chunk size and number</I
></SPAN
>. The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> program, which initializes the
Cache Manager, allows you to control the size and number of chunks into which a cache is divided, plus related parameters.
Setting these parameters is optional, because there are reasonable defaults, but it provides precise control. The AFS
distribution includes configuration scripts that set Cache Manager parameters to values that are reasonable for different
configurations and usage patterns. See <A
HREF="c21473.html#HDRWQ402"
>Setting Other Cache Parameters with the afsd
program</A
>.</P
></LI
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>knowledge of database server machines</I
></SPAN
>. Enable access to a cell's AFS filespace and other
services by listing the cell's database server machines in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/CellServDB</B
></SPAN
>
file on the local disk. See <A
HREF="c21473.html#HDRWQ406"
>Maintaining Knowledge of Database Server Machines</A
>.</P
></LI
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>setuid privilege</I
></SPAN
>. You can control whether the Cache Manager allows programs from a cell to
execute with setuid permission. See <A
HREF="c21473.html#HDRWQ409"
>Determining if a Client Can Run Setuid
Programs</A
>.</P
></LI
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>cell membership</I
></SPAN
>. Each client belongs to a one cell defined by the local <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/ThisCell</B
></SPAN
> file. Cell membership determines the default cell in which the machine's
users are authenticated and in which AFS commands run. See <A
HREF="c21473.html#HDRWQ411"
>Setting a Client Machine's Cell
Membership</A
>.</P
></LI
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>cached file version</I
></SPAN
>. AFS's system of callbacks normally guarantees that the Cache Manager has
the most current versions of files and directories possible. Nevertheless, you can force the Cache Manager to fetch the
most current version of a file from the File Server if you suspect that the cache contains an outdated version. See <A
HREF="c21473.html#HDRWQ412"
>Forcing the Update of Cached Data</A
>.</P
></LI
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>File Server and Volume Location Server preferences</I
></SPAN
>. The Cache Manager sets numerical preference
ranks for the interfaces on file server machines and Volume Server (VL) machines. The ranks determine which interface the
Cache Manager first attempts to use when fetching data from a volume or from the Volume Location Database (VLDB). The
Cache Manager sets default ranks as it initializes, basing them on its network proximity to each interface, but you can
modify the preference ranks if you wish. See <A
HREF="c21473.html#HDRWQ414"
>Maintaining Server Preference Ranks</A
>.</P
></LI
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>interfaces registered with the File Server</I
></SPAN
>. If the Cache Manager is multihomed (has multiple
interface addresses), you can control which of them it registers for File Servers to use when they initiate RPCs to the
client machine. See <A
HREF="c21473.html#HDRWQ415"
>Managing Multihomed Client Machines</A
>.</P
></LI
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>display of information messages</I
></SPAN
>. By default, the Cache Manager sends basic error and
informational messages to the client machine's console and to command shells. You can disable the messaging. See <A
HREF="c21473.html#HDRWQ416"
>Controlling the Display of Warning and Informational Messages</A
>.</P
></LI
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>system type</I
></SPAN
>. The Cache Manager records the local machine's AFS system type in kernel memory,
and substitutes the value for the @sys variable in pathnames. See <A
HREF="c21473.html#HDRWQ417"
>Displaying and Setting the
System Type Name</A
>.</P
></LI
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>delayed writes</I
></SPAN
>. By default, the Cache Manager writes all data to the File Server immediately
and synchronously when an application program closes a file. You can enable asynchronous writes, either for an individual
file, or all files that the Cache Manager handles, and set how much data remains to be written when the Cache Manager
returns control to the closing application. See <A
HREF="c21473.html#HDRWQ418"
>Enabling Asynchronous Writes</A
>.</P
></LI
></UL
></P
><P
>You must make all configuration changes on the client machine itself (at the console or over a direct connection such as a
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>telnet</B
></SPAN
> connection). You cannot configure the Cache Manager remotely. You must be logged in as
the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> to issue some commands, whereas others require no privilege. All files
mentioned in this chapter must actually reside on the local disk of each AFS client machine (they cannot, for example, be
symbolic links to files in AFS).</P
><P
>AFS's <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>package</B
></SPAN
> program can simplify other aspects of client machine configuration,
including those normally set in the machine's AFS initialization file. See <A
HREF="c23832.html"
>Configuring Client Machines
with the package Program</A
>.</P
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="HDRWQ391"
>Configuration and Cache-Related Files on the Local Disk</A
></H1
><P
>This section briefly describes the client configuration files that must reside in the local <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc</B
></SPAN
> directory on every client machine. If the machine uses a disk cache, there must be a
partition devoted to cache files; by convention, it is mounted at the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/cache</B
></SPAN
>
directory.</P
><P
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>Note for Windows users:</B
></SPAN
> Some files described in this document possibly do not exist on
machines that run a Windows operating system. Also, Windows uses a backslash (<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>\</B
></SPAN
>) rather than a
forward slash (<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/</B
></SPAN
>) to separate the elements in a pathname.</P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="HDRWQ392"
>Configuration Files in the /usr/vice/etc Directory</A
></H2
><P
>The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc</B
></SPAN
> directory on a client machine's local disk must contain certain
configuration files for the Cache Manager to function properly. They control the most basic aspects of Cache Manager
configuration.</P
><P
>If it is important that the client machines in your cell perform uniformly, it is most efficient to update these files
from a central source. The following descriptions include pointers to sections that discuss how best to maintain the files.
<DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
></DT
><DD
><P
>The binary file for the program that initializes the Cache Manager. It must run each time the machine reboots in
order for the machine to remain an AFS client machine. The program also initializes several daemons that improve Cache
Manager functioning, such as the process that handles callbacks. </P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cacheinfo</B
></SPAN
></DT
><DD
><P
>A one-line file that sets the cache's most basic configuration parameters: the local directory at which the
Cache Manager mounts the AFS filespace, the local disk directory to use as the cache, and how many kilobytes to
allocate to the cache.</P
><P
>The <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>IBM AFS Quick Beginnings</I
></SPAN
> explains how to create this file as you install a client
machine. To change the cache size on a machine that uses a memory cache, edit the file and reboot the machine. On a
machine that uses a disk cache, you can change the cache size without rebooting by issuing the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setcachesize</B
></SPAN
> command. For instructions, see <A
HREF="c21473.html#HDRWQ394"
>Determining the Cache
Type, Size, and Location</A
>. </P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
></DT
><DD
><P
>This ASCII file names the database server machines in the local cell and in any foreign cell to which you want
to enable access from this machine. (Database server machines are the machines in a cell that run the Authentication,
Backup, Protection, and VL Server processes; see <A
HREF="c3025.html#HDRWQ92"
>Database Server Machines</A
>.)</P
><P
>The Cache Manager must be able to reach a cell's database server machines to fetch files from its filespace.
Incorrect or missing information in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file can slow or completely block
access. It is important to update the file whenever a cell's database server machines change.</P
><P
>As the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> program initializes the Cache Manager, it loads the contents of the
file into kernel memory. The Cache Manager does not read the file between reboots, so to incorporate changes to the
file into kernel memory, you must reboot the machine. Alternatively, you can issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs
newcell</B
></SPAN
> command to insert the changes directly into kernel memory without changing the file. It can also be
convenient to upgrade the file from a central source. For instructions, see <A
HREF="c21473.html#HDRWQ406"
>Maintaining
Knowledge of Database Server Machines</A
>.</P
><P
>(The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file on client machines is not the same as the one kept in the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/afs/etc</B
></SPAN
> directory on server machines, which lists only the local cell's database
server machines. For instructions on maintaining the server <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file, see
<A
HREF="c3025.html#HDRWQ118"
>Maintaining the Server CellServDB File</A
>). </P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>NetInfo</B
></SPAN
></DT
><DD
><P
>This optional ASCII file lists one or more of the network interface addresses on the client machine. If it
exists when the Cache Manager initializes, the Cache Manager uses it as the basis for the list of interfaces that it
registers with File Servers. See <A
HREF="c21473.html#HDRWQ415"
>Managing Multihomed Client Machines</A
>. </P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>NetRestrict</B
></SPAN
></DT
><DD
><P
>This optional ASCII file lists one or more network interface addresses. If it exists when the Cache Manager
initializes, the Cache Manager removes the specified addresses from the list of interfaces that it registers with File
Servers. See <A
HREF="c21473.html#HDRWQ415"
>Managing Multihomed Client Machines</A
>. </P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>ThisCell</B
></SPAN
></DT
><DD
><P
>This ASCII file contains a single line that specifies the complete domain-style name of the cell to which the
machine belongs. Examples are <SAMP
CLASS="computeroutput"
>abc.com</SAMP
> and
<SAMP
CLASS="computeroutput"
>stateu.edu</SAMP
>. This value defines the default cell in which the machine's users become
authenticated, and in which the command interpreters (for example, the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>bos</B
></SPAN
> command)
contact server processes.</P
><P
>The <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>IBM AFS Quick Beginnings</I
></SPAN
> explains how to create this file as you install the AFS client
functionality. To learn about changing a client machine's cell membership, see <A
HREF="c21473.html#HDRWQ411"
>Setting a
Client Machine's Cell Membership</A
>.</P
></DD
></DL
></DIV
></P
><P
>In addition to these files, the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc</B
></SPAN
> directory also sometimes contains the
following types of files and subdirectories: <UL
><LI
><P
>The AFS initialization script, called <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afs.rc</B
></SPAN
> on many system types. In the
conventional configuration specified by the <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>IBM AFS Quick Beginnings</I
></SPAN
>, it is a symbolic link to the
actual script kept in the same directory as other initialization files used by the operating system. </P
></LI
><LI
><P
>A subdirectory that houses AFS kernel library files used by a dynamic kernel loading program. </P
></LI
><LI
><P
>A subdirectory called <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>C</B
></SPAN
>, which houses the Cache Manager catalog file called
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afszcm.cat</B
></SPAN
>. The fstrace program uses the catalog file to translate operation codes into
character strings, which makes the message in the trace log more readable. See <A
HREF="c18360.html#HDRWQ342"
>About the
fstrace Command Suite</A
>.</P
></LI
></UL
></P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="HDRWQ393"
>Cache-Related Files</A
></H2
><P
>A client machine that uses a disk cache must have a local disk directory devoted to the cache. The conventional mount
point is <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/cache</B
></SPAN
>, but you can use another partition that has more available
space.</P
><P
>Do not delete or directly modify any of the files in the cache directory. Doing so can cause a kernel panic, from which
the only way to recover is to reboot the machine. By default, only the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
>
can read the files directly, by virtue of owning them.</P
><P
>A client machine that uses a memory cache keeps all of the information stored in these files in machine memory instead.
<DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CacheItems</B
></SPAN
></DT
><DD
><P
>A binary-format file in which the Cache Manager tracks the contents of cache chunks (the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>V</B
></SPAN
> files in the directory, described just following), including the file ID number (fID) and the
data version number. </P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>VolumeItems</B
></SPAN
></DT
><DD
><P
>A binary-format file in which the Cache Manager records the mapping between mount points and the volumes from
which it has fetched data. The Cache Manager uses the information when responding to the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>pwd</B
></SPAN
> command, among others. </P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>Vn</B
></SPAN
></DT
><DD
><P
>A cache chunk file, which expands to a maximum size (by default, 64 KB) to house data fetched from AFS files.
The number of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>V</B
></SPAN
>n files in the cache depends on the cache size among other factors.
The n is the index assigned to each file; they are numbered sequentially, but the Cache Manager does not necessarily
use them in order or contiguously. If an AFS file is larger than the maximum size for <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>V</B
></SPAN
>n files, the Cache Manager divides it across multiple <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>V</B
></SPAN
>n
files.</P
></DD
></DL
></DIV
></P
></DIV
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="HDRWQ394"
>Determining the Cache Type, Size, and Location</A
></H1
><P
>This section explains how to configure a memory or disk cache, how to display and set the size of either type of cache,
and how to set the location of the cache directory for a disk cache. </P
><P
>The Cache Manager uses a disk cache by default, and it is the preferred type of caching. To configure a memory cache,
include the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-memcache</B
></SPAN
> flag on the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> command, which is
normally invoked in the machine's AFS initialization file. If configured to use a memory cache, the Cache Manager does no disk
caching, even if the machine has a disk.</P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_438"
>Choosing the Cache Size</A
></H2
><P
>Cache size influences the performance of a client machine more directly than perhaps any other cache parameter. The
larger the cache, the faster the Cache Manager is likely to deliver files to users. A small cache can impair performance
because it increases the frequency at which the Cache Manager must discard cached data to make room for newly requested data.
When an application asks for data that has been discarded, the Cache Manager must request it from the File Server, and
fetching data across the network is almost always slower than fetching it from the local disk. The Cache Manager never
discards data from a file that has been modified locally but not yet stored back to the File Server. If the cache is very
small, the Cache Manager possible cannot find any data to discard. For more information about the algorithm it uses when
discarding cached data, see <A
HREF="c21473.html#HDRWQ401"
>How the Cache Manager Chooses Data to Discard</A
>).</P
><P
>The amount of disk or memory you devote to caching depends on several factors. The amount of space available in memory
or on the partition housing the disk cache directory imposes an absolute limit. In addition, you cannot allocate more than 95%
of the space available on the cache directory's partition to a disk cache. The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> program
exits without starting the Cache Manager and prints an appropriate message to the standard output stream if you violate this
restriction. For a memory cache, you must leave enough memory for other processes and applications to run. If you try to
allocate more memory than is actually available, the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> program exits without initializing
the Cache Manager and produces the following message on the standard output stream:</P
><PRE
CLASS="programlisting"
>&#13; afsd: memCache allocation failure at number KB
</PRE
><P
>where number is how many kilobytes were allocated just before the failure.</P
><P
>Within these hard limits, the factors that determine appropriate cache size include the number of users working on the
machine, the size of the files with which they usually work, and (for a memory cache) the number of processes that usually run
on the machine. The higher the demand from these factors, the larger the cache needs to be to maintain good
performance.</P
><P
>Disk caches smaller than 10 MB do not generally perform well. Machines serving multiple users usually perform better
with a cache of at least 60 to 70 MB. The point at which enlarging the cache further does not really improve performance
depends on the factors mentioned previously, and is difficult to predict.</P
><P
>Memory caches smaller than 1 MB are nonfunctional, and the performance of caches smaller than 5 MB is usually
unsatisfactory. Suitable upper limits are similar to those for disk caches but are probably determined more by the demands on
memory from other sources on the machine (number of users and processes). Machines running only a few processes possibly can
use a smaller memory cache.</P
><P
>AFS imposes an absolute limit on cache size in some versions. See the <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>IBM AFS Release Notes</I
></SPAN
> for the
version you are using.</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="HDRWQ395"
>Displaying and Setting the Cache Size and Location</A
></H2
><P
>The Cache Manager determines how big to make the cache by reading the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/cacheinfo</B
></SPAN
> file as it initializes. As directed in the <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>IBM AFS Quick
Beginnings</I
></SPAN
>, you must create the file before running the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> program. The file
also defines the directory on which to mount AFS (by convention, <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/afs</B
></SPAN
>), and the local disk
directory to use for a cache directory.</P
><P
>To change any of the values in the file, log in as the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
>. You must
reboot the machine to have the new value take effect. For instructions, see <A
HREF="c21473.html#HDRWQ398"
>To edit the cacheinfo
file</A
>.</P
><P
>To change the cache size at reboot without editing the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cacheinfo</B
></SPAN
> file, include the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-blocks</B
></SPAN
> argument to the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> command; see the command's
reference page in the IBM AFS Administration Reference.</P
><P
>For a disk cache, you can also use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setcachesize</B
></SPAN
> command to reset the cache size
without rebooting. The value you set persists until the next reboot, at which time the cache size returns to the value
specified in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cacheinfo</B
></SPAN
> file or by the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-blocks</B
></SPAN
> argument
to the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> command. For instructions, see <A
HREF="c21473.html#HDRWQ399"
>To change the disk cache
size without rebooting</A
>.</P
><P
>To display the current cache size and the amount of space the Cache Manager is using at the moment, use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getcacheparms</B
></SPAN
> command as detailed in <A
HREF="c21473.html#HDRWQ397"
>To display the current cache
size</A
>.</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="HDRWQ396"
>To display the cache size set at reboot</A
></H2
><OL
TYPE="1"
><LI
><P
>Use a text editor or the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cat</B
></SPAN
> command to display the contents of the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/cacheinfo</B
></SPAN
> file. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cat /usr/vice/etc/cacheinfo</B
></SPAN
>
</PRE
></P
></LI
></OL
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="HDRWQ397"
>To display the current cache size</A
></H2
><OL
TYPE="1"
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getcacheparms</B
></SPAN
> command on the client machine. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getcacheparms</B
></SPAN
>
</PRE
></P
><P
>where <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>getca</B
></SPAN
> is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>getcacheparms</B
></SPAN
>.</P
><P
>The output shows the number of kilobyte blocks the Cache Manager is using as a cache at the moment the command is
issued, and the current size of the cache. For example:</P
><PRE
CLASS="programlisting"
>&#13; AFS using 13709 of the cache's available 15000 1K byte blocks.
</PRE
></LI
></OL
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="HDRWQ398"
>To edit the cacheinfo file</A
></H2
><OL
TYPE="1"
><LI
><P
>Become the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> on the machine, if you are not already, by issuing
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su root</B
></SPAN
>
Password: &#60;<VAR
CLASS="replaceable"
>root_password</VAR
>&#62;
</PRE
></P
></LI
><LI
><P
>Use a text editor to edit the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/cacheinfo</B
></SPAN
> file, which has three fields,
separated by colons: <UL
><LI
><P
>The first field names the local directory on which to mount the AFS filespace. The conventional location is
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/afs</B
></SPAN
>.</P
></LI
><LI
><P
>The second field defines the local disk directory to use for the disk cache. The conventional location is the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/cache</B
></SPAN
> directory, but you can specify an alternate directory if another
partition has more space available. There must always be a value in this field, but the Cache Manager ignores it if
the machine uses a memory cache.</P
></LI
><LI
><P
>The third field defines cache size as a number of kilobyte (1024-byte) blocks.</P
></LI
></UL
></P
><P
>The following example mounts the AFS filespace at the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/afs</B
></SPAN
> directory, names
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/cache</B
></SPAN
> as the cache directory, and sets cache size to 50,000 KB:</P
><PRE
CLASS="programlisting"
>&#13; <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/afs:/usr/vice/cache:50000</B
></SPAN
>
</PRE
></LI
></OL
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="HDRWQ399"
>To change the disk cache size without rebooting</A
></H2
><OL
TYPE="1"
><LI
><P
>Become the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> on the machine, if you are not already, by issuing
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su root</B
></SPAN
>
Password: &#60;<VAR
CLASS="replaceable"
>root_password</VAR
>&#62;
</PRE
></P
></LI
><LI
><P
><A
NAME="LIWQ400"
></A
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setcachesize</B
></SPAN
> command to set a new disk cache
size.</P
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>This command does not work for a memory cache.</P
></BLOCKQUOTE
></DIV
><PRE
CLASS="programlisting"
>&#13; # <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setcachesize</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>size in 1K byte blocks (0 =</VAR
>&#62; reset)&#62;
</PRE
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>setca</B
></SPAN
></DT
><DD
><P
>Is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>setcachesize</B
></SPAN
>.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>size in 1K byte blocks (0 =&#62; reset)</B
></SPAN
></DT
><DD
><P
>Sets the number of kilobyte blocks to be used for the cache. Specify a positive integer (<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>1024</B
></SPAN
> equals 1 MB), or <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>0</B
></SPAN
> (zero) to reset the cache size to
the value specified in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cacheinfo</B
></SPAN
> file.</P
></DD
></DL
></DIV
></P
></LI
></OL
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_444"
>To reset the disk cache size to the default without rebooting</A
></H2
><OL
TYPE="1"
><LI
><P
>Become the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> on the machine, if you are not already, by issuing
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su root</B
></SPAN
>
Password: &#60;<VAR
CLASS="replaceable"
>root_password</VAR
>&#62;
</PRE
></P
></LI
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setcachesize</B
></SPAN
> command to reset the size of the local disk cache (the
command does not work for a memory cache). Choose one of the two following options: <UL
><LI
><P
>To reset the cache size to the value specified in the local <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cacheinfo</B
></SPAN
> file,
specify the value <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>0</B
></SPAN
> (zero) <PRE
CLASS="programlisting"
>&#13; # <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setcachesize 0</B
></SPAN
>
</PRE
></P
></LI
><LI
><P
>To reset the cache size to the value set at the last reboot of the machine, include the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-reset</B
></SPAN
> flag. Unless the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-blocks</B
></SPAN
> argument was used on the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> command, this is also the value in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cacheinfo</B
></SPAN
> file. <PRE
CLASS="programlisting"
>&#13; # <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setcachesize -reset</B
></SPAN
>
</PRE
></P
></LI
></UL
></P
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>setca</B
></SPAN
></DT
><DD
><P
>Is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>setcachesize</B
></SPAN
>.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>0</B
></SPAN
></DT
><DD
><P
>Resets the disk cache size to the value in the third field of the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/cacheinfo</B
></SPAN
> file.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-reset</B
></SPAN
></DT
><DD
><P
>Resets the cache size to the value set at the last reboot.</P
></DD
></DL
></DIV
></P
></LI
></OL
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="HDRWQ401"
>How the Cache Manager Chooses Data to Discard</A
></H2
><P
>When the cache is full and application programs request more data from AFS, the Cache Manager must flush out cache
chunks to make room for the data. The Cache Manager considers two factors: <OL
TYPE="1"
><LI
><P
>How recently an application last accessed the data.</P
></LI
><LI
><P
>Whether the chunk is <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>dirty</I
></SPAN
>. A dirty chunk contains changes to a file that have not yet been
saved back to the permanent copy stored on a file server machine.</P
></LI
></OL
></P
><P
>The Cache Manager first checks the least-recently used chunk. If it is not dirty, the Cache Manager discards the data in
that chunk. If the chunk is dirty, the Cache Manager moves on to check the next least recently used chunk. It continues in
this manner until it has created a sufficient number of empty chunks.</P
><P
>Chunks that contain data fetched from a read-only volume are by definition never dirty, so the Cache Manager can always
discard them. Normally, the Cache Manager can also find chunks of data fetched from read/write volumes that are not dirty, but
a small cache makes it difficult to find enough eligible data. If the Cache Manager cannot find any data to discard, it must
return I/O errors to application programs that request more data from AFS. Application programs usually have a means for
notifying the user of such errors, but not for revealing their cause.</P
></DIV
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="HDRWQ402"
>Setting Other Cache Parameters with the afsd program</A
></H1
><P
>There are only three cache configuration parameters you must set: the mount directory for AFS, the location of the disk
cache directory, and the cache size. They correspond to the three fields in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/cacheinfo</B
></SPAN
> file, as discussed in <A
HREF="c21473.html#HDRWQ394"
>Determining the Cache Type, Size,
and Location</A
>. However, if you want to experiment with fine-tuning cache performance, you can use the arguments on the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> command to control several other parameters. This section discusses a few of these
parameters that have the most direct effect on cache performance. To learn more about the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
>
command's arguments, see its reference page in the <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>IBM AFS Administration Reference</I
></SPAN
>.</P
><P
>In addition, the AFS initialization script included in the AFS distribution for each system type includes several
variables that set several <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> arguments in a way that is suitable for client machines of
different sizes and usage patterns. For instructions on using the script most effectively, see the section on configuring the
Cache Manager in the <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>IBM AFS Quick Beginnings</I
></SPAN
>.</P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="HDRWQ403"
>Setting Cache Configuration Parameters</A
></H2
><P
>The cache configuration parameters with the most direct effect on cache performance include the following: <UL
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>total cache size</I
></SPAN
>. This is the amount of disk space or machine memory available for caching,
as discussed in detail in <A
HREF="c21473.html#HDRWQ394"
>Determining the Cache Type, Size, and Location</A
>.</P
></LI
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>number of cache chunks</I
></SPAN
>. For a disk cache, each chunk is a <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>V</B
></SPAN
>n
file in the local cache directory (see <A
HREF="c21473.html#HDRWQ393"
>Cache-Related Files</A
>). For a memory cache, each
chunk is a set of contiguous blocks allocated in machine memory.</P
><P
>This parameter does not have as much of an effect on cache performance as total size. However, adjusting it can
influence how often the Cache Manager must discard cached data to make room for new data. Suppose, for example, that you
set the disk cache size to 50 MB and the number of chunks (<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>V</B
></SPAN
>n files) to 1,000. If each
of the ten users on the machine caches 100 AFS files that average 20 KB in size, then all 1,000 chunks are full (a chunk
can contain data from only one AFS file) but the cache holds only about 20 MB of data. When a user requests more data
from the File Server, the Cache Manager must discard cached data to reclaim some chunks, even though the cache is filled
to less than 50% of its capacity. In such a situation, increasing the number of chunks enables the Cache Manager to
discard data less often.</P
></LI
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>chunk size</I
></SPAN
>. This parameter determines the maximum amount of data that can fit in a chunk. If
a cached element is smaller than the chunk size, the remaining space in the chunk is not used (a chunk can hold no more
than one element). If an element cannot fit in a single chunk, it is split across as many chunks as needed. This
parameter also determines how much data the Cache Manager requests at a time from the File Server (how much data per
<SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>fetch RPC</I
></SPAN
>, because AFS uses partial file transfer).</P
><P
>The main reason to change chunk size is because of its relation to the amount of data fetched per RPC. If your
network links are very fast, it can improve performance to increase chunk size; if the network is especially slow, it
can make sense to decrease chunk size.</P
></LI
><LI
><P
><SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>number of dcache entries in memory</I
></SPAN
>. The Cache Manager maintains one dcache entry for each
cache chunk, recording a small amount of information, such as the file ID (fID) and version number of the AFS file
corresponding to the chunk.</P
><P
>For a disk cache, dcache entries reside in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/cache/CacheItems</B
></SPAN
> file; a
small number are duplicated in machine memory to speed access.</P
><P
>For a memory cache, the number of dcache entries equals the number of cache chunks. For a discussion of the
implications of this correspondence, see <A
HREF="c21473.html#HDRWQ405"
>Controlling Memory Cache Configuration</A
>.</P
></LI
></UL
></P
><P
>For a description of how the Cache Manager determines defaults for number of chunks, chunk size, and number of dcache
entries in a disk cache, see <A
HREF="c21473.html#HDRWQ404"
>Configuring a Disk Cache</A
>; for a memory cache, see <A
HREF="c21473.html#HDRWQ405"
>Controlling Memory Cache Configuration</A
>. The instructions also explain how to use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> command's arguments to override the defaults.</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="HDRWQ404"
>Configuring a Disk Cache</A
></H2
><P
>The default number of cache chunks (<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>V</B
></SPAN
>n files) in a disk cache is calculated by the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> command to be the greatest of the following: <UL
><LI
><P
>100</P
></LI
><LI
><P
>1.5 times the result of dividing cache size by chunk size (cachesize/chunksize * 1.5)</P
></LI
><LI
><P
>The result of dividing cachesize by 10 MB (cachesize/10240)</P
></LI
></UL
></P
><P
>You can override this value by specifying a positive integer with the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-files</B
></SPAN
> argument.
Consider increasing this value if more than 75% of the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>V</B
></SPAN
>n files are already used soon after
the Cache Manager finishes initializing. Consider decreasing it if only a small percentage of the chunks are used at that
point. In any case, never specify a value less than 100, because a smaller value can cause performance problems.</P
><P
>The following example sets the number of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>V</B
></SPAN
>n files to 2,000:</P
><PRE
CLASS="programlisting"
>&#13; <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/afsd -files 2000</B
></SPAN
>
</PRE
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>It is conventional to place the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> command in a machine's AFS initialization file,
rather than entering it in a command shell. Furthermore, the values specified in this section are examples only, and are not
necessarily suitable for a specific machine.</P
></BLOCKQUOTE
></DIV
><P
>The default chunk size for a disk cache is 64 KB. In general, the only reason to change it is to adjust to exceptionally
slow or fast networks; see <A
HREF="c21473.html#HDRWQ403"
>Setting Cache Configuration Parameters</A
>. You can use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-chunksize</B
></SPAN
> argument to override the default. Chunk size must be a power of 2, so provide an integer
between 0 (zero) and 30 to be used as an exponent of 2. For example, a value of 10 sets chunk size to 1 KB (210 = 1024); a
value of 16 equals the default for disk caches (216 = 64 KB). Specifying a value of 0 (zero) or greater than 30 returns chunk
size to the default. Values less than 10 (1 KB) are not recommended. The following example sets chunk size to 16 KB
(214):</P
><PRE
CLASS="programlisting"
>&#13; <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/afsd -chunksize 14</B
></SPAN
>
</PRE
><P
>For a disk cache, the default number of dcache entries duplicated in memory is one-half the number of chunks specified
with the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-files</B
></SPAN
> argument, to a maximum of 2,000 entries. You can use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-dcache</B
></SPAN
> argument to change the default, even exceeding 2,000 if you wish. Duplicating more than half
the dcache entries in memory is not usually necessary, but sometimes improves performance slightly, because access to memory
is faster than access to disk. The following example sets the number to 750:</P
><PRE
CLASS="programlisting"
>&#13; <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/afsd -dcache 750</B
></SPAN
>
</PRE
><P
>When configuring a disk cache, you can combine the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> command's arguments in any way.
The main reason for this flexibility is that the setting you specify for disk cache size (in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cacheinfo</B
></SPAN
> file or with the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-blocks</B
></SPAN
> argument) is an absolute maximum
limit. You cannot override it by specifying higher values for the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-files</B
></SPAN
> or <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-chunksize</B
></SPAN
> arguments, alone or in combination. A related reason is that the Cache Manager does not have
to reserve a set amount of memory on disk. <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>V</B
></SPAN
>n files (the chunks in a disk cache) are
initially zero-length, but can expand up to the specified chunk size and shrink again, as needed. If you set the number of
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>V</B
></SPAN
>n files to such a large value that expanding all of them to the full allowable size exceeds
the total cache size, they simply never grow to full size.</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="HDRWQ405"
>Controlling Memory Cache Configuration</A
></H2
><P
>Configuring a memory cache differs from configuring a disk cache in that not all combinations of the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> command's arguments are allowed. This limitation results from the greater interaction between the
configuration parameters in a memory cache than a disk cache. If all combinations are allowed, it is possible to set the
parameters in an inconsistent way. A list of the acceptable and unacceptable combinations follows a discussion of default
values.</P
><P
>The default chunk size for a memory cache is 8 KB. In general, the only reason to change it is to adjust to
exceptionally slow or fast networks; see <A
HREF="c21473.html#HDRWQ403"
>Setting Cache Configuration Parameters</A
>.</P
><P
>There is no predefined default for number of chunks in a memory cache. The Cache Manager instead calculates the correct
number by dividing the total cache size by the chunk size. Recall that for a memory cache, all dcache entries must be in
memory. This implies that the number of chunks equals the number of dcache entries in memory, and that there is no default for
number of dcache entries (like the number of chunks, it is calculated by dividing the total size by the chunk size).</P
><P
>The following are acceptable combinations of the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> command's arguments when
configuring a memory cache: <UL
><LI
><P
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-blocks</B
></SPAN
> alone, which overrides the cache size specified in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/cacheinfo</B
></SPAN
> file. The Cache Manager divides the value of this argument by the default
chunk size of eight KB to calculate the number of chunks and dcache entries. The following example sets cache size to
five MB (5,120 KB) and the number of chunks to 640 (5,120 divided by 8): <PRE
CLASS="programlisting"
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/afsd -memcache -blocks 5120</B
></SPAN
></PRE
></P
></LI
><LI
><P
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-chunksize</B
></SPAN
> alone, to override the default of eight KB. The chunk size must be a
power of two, so provide an integer between 0 (zero) and 30 to be used as an exponent of two. For example, a value of
ten sets chunk size to 1 KB (210 = 1024); a value of 13 equals the default for memory caches (213 = 8 KB). Specifying a
value of 0 (zero) or greater than 30 returns the chunk size to the default. Values less than ten (equivalent to 1 KB)
are not recommended. The following example sets the chunk size to four KB (212). Assuming a total cache size of four MB
(4,096 KB), the resulting number of chunks is 1024. <PRE
CLASS="programlisting"
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/afsd -memcache -chunksize 12</B
></SPAN
></PRE
></P
></LI
><LI
><P
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-blocks</B
></SPAN
> and <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-chunksize</B
></SPAN
> together override the
defaults for cache size and chunk size. The Cache Manager divides the first by the second to calculate the number of
chunks and dcache entries. For example, the following example sets the cache size to six MB (6,144 KB) and chunksize to
four KB (212), resulting in 1,536 chunks: <PRE
CLASS="programlisting"
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/afsd -memcache -blocks 6144 -chunksize 12</B
></SPAN
></PRE
></P
></LI
></UL
></P
><P
>The following arguments or combinations explicitly set the number of chunks and dcache entries. It is best not to use
them, because they set the cache size indirectly, forcing you to perform a hand calculation to determine the size of the
cache. Instead, set the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-blocks</B
></SPAN
> and <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-chunksize</B
></SPAN
> arguments
alone or in combination; in those cases, the Cache Manager determines the number of chunks and dcache entries itself. Because
the following combinations are not recommended, no examples are included. <UL
><LI
><P
>The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-dcache</B
></SPAN
> argument alone explicitly sets the number of chunks and dcache
entries. The Cache Manager multiples this value times the default chunk size of 8 KB to derive the total cache size
(overriding the value in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cacheinfo</B
></SPAN
> file).</P
></LI
><LI
><P
>The combination of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-dcache</B
></SPAN
> and <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-chunksize</B
></SPAN
> sets
the chunk number and size. The Cache Manager sets the specified values and multiplies them together to obtain total
cache size (overriding the value in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cacheinfo</B
></SPAN
> file).</P
></LI
></UL
></P
><P
>Do not use the following arguments for a memory cache: <UL
><LI
><P
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-files</B
></SPAN
> alone. This argument controls the number of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>V</B
></SPAN
>n files for a disk cache, but is ignored for a memory cache.</P
></LI
><LI
><P
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-blocks</B
></SPAN
> and <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-dcache</B
></SPAN
>. An error message results,
because it is possible to provide values such that dividing the first (total size) by the second (number of chunks)
results in a chunk size that is not a power of two.</P
></LI
></UL
></P
></DIV
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="HDRWQ406"
>Maintaining Knowledge of Database Server Machines</A
></H1
><P
>For the users of an AFS client machine to access a cell's AFS filespace and other services, the Cache Manager and other
client-side agents must have an accurate list of the cell's database server machines. The affected functions include the
following: <UL
><LI
><P
>Accessing files. The Cache Manager contacts the Volume Location (VL) Server to learn which file server machine
houses the volume containing a requested file or directory. If the Cache Manager cannot contact a cell's VL Servers, it
cannot fetch files.</P
></LI
><LI
><P
>Authenticating. The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>klog</B
></SPAN
> program and AFS-modified login utilities contact the
Authentication Server to obtain tokens, which the AFS server processes accept as proof that the user is
authenticated.</P
></LI
><LI
><P
>Creating protection groups. The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>pts</B
></SPAN
> command interpreter contacts the Protection
Server when users create protection groups or request information from the Protection Database.</P
></LI
><LI
><P
>Editing access control lists (ACLs). The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs</B
></SPAN
> command interpreter contacts the File
Server that maintains the read/write volume containing a file or directory; the location information comes from the VL
Server.</P
></LI
></UL
></P
><P
>To enable a machine's users to access a cell, you must list the names and IP addresses of its database server machines in
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/CellServDB</B
></SPAN
> file on the machine's local disk. In addition to the machine's
home cell, you can list any foreign cells that you want to enable users to access. (To enable access to a cell's filespace, you
must also mount its <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root.cell</B
></SPAN
> volume in the local AFS filespace; the conventional location is
just under the AFS root directory, <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/afs</B
></SPAN
>. For instructions, see the <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>IBM AFS Quick
Beginnings</I
></SPAN
>.)</P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_451"
>How Clients Use the List of Database Server Machines</A
></H2
><P
>As the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> program runs and initializes the Cache Manager, it reads the contents of
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file into kernel memory. The Cache Manager does not consult the file again
until the machine next reboots. In contrast, the command interpreters for the AFS command suites (such as <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs</B
></SPAN
> and <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>pts</B
></SPAN
>) read the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file
each time they need to contact a database server process.</P
><P
>When a cell's list of database server machines changes, you must change both the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file and the list in kernel memory to preserve consistent client performance; some commands
probably fail if the two lists of machines disagree. One possible method for updating both the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file and kernel memory is to edit the file and reboot the machine. To avoid needing to
reboot, you can instead perform both of the following steps: <OL
TYPE="1"
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs newcell</B
></SPAN
> command to alter the list in kernel memory directly, making
the changes available to the Cache Manager.</P
></LI
><LI
><P
>Edit the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file to make the changes available to command interpreters.
For a description of the file's format, see <A
HREF="c21473.html#HDRWQ407"
>The Format of the CellServDB file</A
>.</P
></LI
></OL
></P
><P
>The consequences of missing or incorrect information in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file or kernel
memory are as follows: <UL
><LI
><P
>If there is no entry for a cell, the machine's users cannot access the cell.</P
></LI
><LI
><P
>If a cell's entry does not include a database server machine, then the Cache Manager and command interpreters
never attempt to contact the machine. The omission does not prevent access to the cell--as long as the information about
the other database server machines is correct and the server processes, machines, and network are functioning
correctly--but it can put an undue burden on the machines that are listed. If all of the listed machines become
inaccessible to clients, then the cell becomes inaccessible even if the omitted database server machine is functioning
correctly.</P
></LI
><LI
><P
>If a machine's name or address is incorrect, or the machine is not actually running the database server processes,
then requests from clients time out. Users can experience lengthy delays because they have to wait the full timeout
period before the Cache Manager or command interpreter contacts another database server machine.</P
></LI
></UL
></P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="HDRWQ407"
>The Format of the CellServDB file</A
></H2
><P
>When editing the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/CellServDB</B
></SPAN
> file, you must use the correct format for
cell and machine entries. Each cell has a separate entry. The first line has the following format:</P
><PRE
CLASS="programlisting"
>&#13; &#62;cell_name #organization
</PRE
><P
>where cell_name is the cell's complete Internet domain name (for example, <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>abc.com</B
></SPAN
>) and
organization is an optional field that follows any number of spaces and the number sign (<SAMP
CLASS="computeroutput"
>#</SAMP
>)
and can name the organization to which the cell corresponds (for example, the ABC Corporation). After the first line comes a
separate line for each database server machine. Each line has the following format:</P
><PRE
CLASS="programlisting"
>&#13; IP_address #machine_name
</PRE
><P
>where IP_address is the machine's IP address in dotted decimal format (for example, 192.12.105.3). Following any number
of spaces and the number sign (<SAMP
CLASS="computeroutput"
>#</SAMP
>) is machine_name, the machine's fully-qualified hostname
(for example, <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>db1.abc.com</B
></SPAN
>). In this case, the number sign does not indicate a comment:
machine_name is a required field.</P
><P
>The order in which the cells appear is not important, but it is convenient to put the client machine's home cell first.
Do not include any blank lines in the file, not even after the last entry.</P
><P
>The following example shows entries for two cells, each of which has three database server machines:</P
><PRE
CLASS="programlisting"
>&#13; &#62;abc.com #ABC Corporation (home cell)
192.12.105.3 #db1.abc.com
192.12.105.4 #db2.abc.com
192.12.105.55 #db3.abc.com
&#62;stateu.edu #State University cell
138.255.68.93 #serverA.stateu.edu
138.255.68.72 #serverB.stateu.edu
138.255.33.154 #serverC.stateu.edu
</PRE
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="HDRWQ408"
>Maintaining the Client CellServDB File</A
></H2
><P
>Because a correct entry in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file is vital for consistent client
performance, you must also update the file on each client machine whenever a cell's list of database server machines changes
(for instance, when you follow the instructions in the <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>IBM AFS Quick Beginnings</I
></SPAN
> to add or remove a
database server machine). To facilitate the client updates, you can use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>package</B
></SPAN
> program,
which copies files from a central source in AFS to the local disk of client machines. It is conventional to invoke the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>package</B
></SPAN
> program in a client machine's AFS initialization file so that it runs as the machine
reboots, but you can also issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>package</B
></SPAN
> command at any time. For instructions, see <A
HREF="c23832.html#HDRWQ448"
>Running the package program</A
>.</P
><P
>If you use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>package</B
></SPAN
> program, the conventional location for your cell's central
source <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file is <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/afs/</B
></SPAN
>cell_name<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/common/etc/CellServDB</B
></SPAN
>, where cell_name is your cell name. </P
><P
>Creating a symbolic or hard link from <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/CellServDB</B
></SPAN
> to a central source file
in AFS is not a viable option. The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> program reads the file into kernel memory before the
Cache Manager is completely initialized and able to access AFS.</P
><P
>Because every client machine has its own copy of the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file, you can in theory
make the set of accessible cells differ on various machines. In most cases, however, it is best to maintain consistency
between the files on all client machines in the cell: differences between machines are particularly confusing if users
commonly use a variety of machines rather than just one.</P
><P
>The AFS Product Support group maintains a central <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file that includes all
cells that have agreed to make their database server machines access to other AFS cells. It is advisable to check this file
periodically for updated information. See <A
HREF="c667.html#HDRWQ38"
>Making Your Cell Visible to Others</A
>. </P
><P
>An entry in the local <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> is one of the two requirements for accessing a cell.
The other is that the cell's <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root.cell</B
></SPAN
> volume is mounted in the local filespace, by
convention as a subdirectory of the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/afs</B
></SPAN
> directory. For instructions, see <A
HREF="c8420.html#HDRWQ213"
>To create a cellular mount point</A
>.</P
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/CellServDB</B
></SPAN
> file on a client machine is not the same as the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/afs/etc/CellServDB</B
></SPAN
> file on the local disk of a file server machine. The server version
lists only the database server machines in the server machine's home cell, because server processes never need to contact
foreign cells. It is important to update both types of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file on all machines in
the cell whenever there is a change to your cell's database server machines. For more information about maintaining the
server version of the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file, see <A
HREF="c3025.html#HDRWQ118"
>Maintaining the Server
CellServDB File</A
>.</P
></BLOCKQUOTE
></DIV
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_454"
>To display the /usr/vice/etc/CellServDB file</A
></H2
><OL
TYPE="1"
><LI
><P
>Use a text editor or the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cat</B
></SPAN
> command to display the contents of the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/CellServDB</B
></SPAN
> file. By default, the mode bits on the file permit anyone to read it.
<PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cat /usr/vice/etc/CellServDB</B
></SPAN
>
</PRE
></P
></LI
></OL
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_455"
>To display the list of database server machines in kernel memory</A
></H2
><OL
TYPE="1"
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs listcells</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs listcells [&#38;]</B
></SPAN
>
</PRE
></P
><P
>where <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>listc</B
></SPAN
> is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>listcells</B
></SPAN
>.</P
><P
>To have your shell prompt return immediately, include the ampersand (<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>&#38;</B
></SPAN
>), which
makes the command run in the background. It can take a while to generate the complete output because the kernel stores
database server machines' IP addresses only, and the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs</B
></SPAN
> command interpreter has the
cell's name resolution service (such as the Domain Name Service or a local host table) translate them into hostnames. You
can halt the command at any time by issuing an interrupt signal such as <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>Ctrl-c</B
></SPAN
>.</P
><P
>The output includes a single line for each cell, in the following format:</P
><PRE
CLASS="programlisting"
>&#13; Cell cell_name on hosts list_of_hostnames.
</PRE
><P
>The name service sometimes returns hostnames in uppercase letters, and if it cannot resolve a name at all, it
returns its IP address. The following example illustrates all three possibilities:</P
><PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs listcells</B
></SPAN
>
.
.
Cell abc.com on hosts db1.abc.com db2.abc.com db3.abc.com
Cell stateu.edu on hosts SERVERA.STATEU.EDU SERVERB.STATEU.EDU
SERVERC.STATEU.EDU
Cell ghi.org on hosts 191.255.64.111 191.255.64.112
.
.
</PRE
></LI
></OL
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_456"
>To change the list of a cell's database server machines in kernel memory</A
></H2
><OL
TYPE="1"
><LI
><P
>Become the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> on the machine, if you are not already, by issuing
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su root</B
></SPAN
>
Password: &#60;<VAR
CLASS="replaceable"
>root_password</VAR
>&#62;
</PRE
></P
></LI
><LI
><P
>If you a use a central copy of the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file as a source for client machines,
verify that its directory's ACL grants you the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>l</B
></SPAN
> (<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>lookup</B
></SPAN
>), <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>r</B
></SPAN
> (<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>read</B
></SPAN
>), and <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>w</B
></SPAN
> (<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>write</B
></SPAN
>) permissions. The conventional directory is <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/afs/</B
></SPAN
>cell_name<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/common/etc</B
></SPAN
>. If necessary, issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs listacl</B
></SPAN
> command, which is fully described in <A
HREF="c31274.html#HDRWQ572"
>Displaying ACLs</A
>.
<PRE
CLASS="programlisting"
>&#13; # <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs listacl</B
></SPAN
> [&#60;<VAR
CLASS="replaceable"
>dir/file path</VAR
>&#62;]
</PRE
> </P
></LI
><LI
><P
><A
NAME="LINEWCELL"
></A
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs newcell</B
></SPAN
> command to add or change a cell's
entry in kernel memory. Repeat the command for each cell.</P
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>You cannot use this command to remove a cell's entry completely from kernel memory. In the rare cases when you
urgently need to prevent access to a specific cell, you must edit the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file
and reboot the machine.</P
></BLOCKQUOTE
></DIV
><PRE
CLASS="programlisting"
>&#13; # <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs newcell</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>cell name</VAR
>&#62; &#60;<VAR
CLASS="replaceable"
>primary servers</VAR
>&#62;+ \
[<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-linkedcell</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>linked cell name</VAR
>&#62;]
</PRE
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>n</B
></SPAN
></DT
><DD
><P
>Is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>newcell</B
></SPAN
>.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cell name</B
></SPAN
></DT
><DD
><P
>Specifies the complete Internet domain name of the cell for which to record a new list of database server
machines.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>primary servers</B
></SPAN
></DT
><DD
><P
>Specifies the fully-qualified hostname or IP address in dotted-decimal format for each database server
machine in the cell. The list you provide completely replaces the existing list.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-linkedcell</B
></SPAN
></DT
><DD
><P
>Specifies the complete Internet domain name of the AFS cell to link to a DCE cell for the purposes of DFS
fileset location. You can use this argument if the machine's AFS users access DFS via the AFS/DFS Migration
Toolkit Protocol Translator. For instructions, see the <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>IBM AFS/DFS Migration Toolkit Administration
Guide and Reference</I
></SPAN
>.</P
></DD
></DL
></DIV
></P
></LI
><LI
><P
>Add or edit the cell's entry in the local <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/CellServDB</B
></SPAN
> file, using one
of the following three methods. In each case, be sure to obey the formatting requirements described in <A
HREF="c21473.html#HDRWQ407"
>The Format of the CellServDB file</A
>. <UL
><LI
><P
>If you maintain a central source version of the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file and use the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>package</B
></SPAN
> program, first use a text editor to alter the central copy of the file.
Then issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>package</B
></SPAN
> command to transfer the contents of the file to the local
machine. For complete instructions, see <A
HREF="c23832.html#HDRWQ448"
>Running the package program</A
>.
<PRE
CLASS="programlisting"
>&#13; # <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/etc/package -v -c</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>name of package file</VAR
>&#62;
</PRE
></P
></LI
><LI
><P
>If you maintain a central source <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file but do not use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>package</B
></SPAN
> program, first use a text editor to alter the central copy of the file. Then use a
copying command such as the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cp</B
></SPAN
> command to copy it to the local <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/CellServDB</B
></SPAN
> file.</P
></LI
><LI
><P
>If you do not use a central source <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>CellServDB</B
></SPAN
> file, edit the local machine's
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/CellServDB</B
></SPAN
> file directly.</P
></LI
></UL
></P
></LI
></OL
></DIV
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="HDRWQ409"
>Determining if a Client Can Run Setuid Programs</A
></H1
><P
>A <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>setuid program</I
></SPAN
> is one whose binary file has the UNIX setuid mode bit turned on. While a setuid
program runs, the user who initialized it assumes the local identity (UNIX UID) of the binary file's owner, and so is granted
the permissions in the local file system that pertain to the owner. Most commonly, the issuer's assumed identity (often referred
to as <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>effective UID</I
></SPAN
>) is the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
>.</P
><P
>AFS does not recognize effective UID: if a setuid program accesses AFS files and directories, it uses the current AFS
identity of the user who initialized the program, not of the program's owner. Nevertheless, it can be useful to store setuid
programs in AFS for use on more than one client machine. AFS enables a client machine's administrator to determine whether the
local Cache Manager allows setuid programs to run or not.</P
><P
>By default, the Cache Manager allows programs from its home cell to run with setuid permission, but denies setuid
permission to programs from foreign cells. A program belongs to the same cell as the file server machine that houses the volume
in which the file resides, as specified in the file server machine's <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/afs/etc/ThisCell</B
></SPAN
>
file. The Cache Manager determines its own home cell by reading the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/ThisCell</B
></SPAN
> file
at initialization.</P
><P
>To change a cell's setuid status with respect to the local machine, become the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> and issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setcell</B
></SPAN
> command. To determine a cell's current
setuid status, use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getcellstatus</B
></SPAN
> command.</P
><P
>When you issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setcell</B
></SPAN
> command, you directly alter a cell's setuid status as
recorded in kernel memory, so rebooting the machine is not necessary. However, nondefault settings do not persist across reboots
of the machine unless you add the appropriate <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setcell</B
></SPAN
> command to the machine's AFS
initialization file.</P
><P
>Only members of the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>system:administrators</B
></SPAN
> group can turn on the setuid mode bit on an AFS
file or directory. When the setuid mode bit is turned on, the UNIX <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>ls -l</B
></SPAN
> command displays the
third user mode bit as an <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>s</B
></SPAN
> instead of an <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>x</B
></SPAN
>, but for an AFS
file or directory, the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>s</B
></SPAN
> appears only if setuid permission is enabled for the cell in which the
file resides. </P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_458"
>To determine a cell's setuid status</A
></H2
><OL
TYPE="1"
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getcellstatus</B
></SPAN
> command to check the setuid status of each desired cell.
<PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getcellstatus</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>cell name</VAR
>&#62;
</PRE
></P
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>getce</B
></SPAN
></DT
><DD
><P
>Is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>getcellstatus</B
></SPAN
>.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cell name</B
></SPAN
></DT
><DD
><P
>Names each cell for which to report setuid status. Provide the complete Internet domain name or a shortened
form that distinguishes it from the other cells listed in the local <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/CellServDB</B
></SPAN
> file.</P
></DD
></DL
></DIV
></P
></LI
></OL
><P
>The output reports the setuid status of each cell: <UL
><LI
><P
>the string <SAMP
CLASS="computeroutput"
>no setuid allowed</SAMP
> indicates that the Cache Manager does not allow
programs from the cell to run with <SAMP
CLASS="computeroutput"
>setuid permission</SAMP
></P
></LI
><LI
><P
>setuid allowed indicates that the Cache Manager allows programs from the cell to run with setuid permission</P
></LI
></UL
></P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_459"
>To change a cell's setuid status</A
></H2
><OL
TYPE="1"
><LI
><P
>Become the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> on the machine, if you are not already, by issuing
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su root</B
></SPAN
>
Password: &#60;<VAR
CLASS="replaceable"
>root_password</VAR
>&#62;
</PRE
></P
></LI
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setcell</B
></SPAN
> command to change the setuid status of the cell.
<PRE
CLASS="programlisting"
>&#13; # <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setcell</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>cell name</VAR
>&#62;+ [<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-suid</B
></SPAN
>] [<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-nosuid</B
></SPAN
>]
</PRE
></P
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>setce</B
></SPAN
></DT
><DD
><P
>Is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>setcell</B
></SPAN
>.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cell name</B
></SPAN
></DT
><DD
><P
>Names each cell for which to change setuid status as specified by the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-suid</B
></SPAN
>
or <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-nosuid</B
></SPAN
> flag. Provide each cell's complete Internet domain name or a shortened
form that distinguishes it from the other cells listed in the local <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/CellServDB</B
></SPAN
> file.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-suid</B
></SPAN
></DT
><DD
><P
>Enables programs from each specified cell to execute with setuid permission. Provide this flag or the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-nosuid</B
></SPAN
> flag, or omit both to disable setuid permission for each cell.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-nosuid</B
></SPAN
></DT
><DD
><P
>Prevents programs from each specified cell from executing with setuid permission. Provide this flag or the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-suid</B
></SPAN
> flag, or omit both to disable setuid permission for each cell.</P
></DD
></DL
></DIV
></P
></LI
></OL
></DIV
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="HDRWQ410"
>Setting the File Server Probe Interval</A
></H1
><P
>The Cache Manager periodically sends a probe to server machines to verify that they are still accessible. Specifically, it
probes the database server machines in its cell and those file servers that house data it has cached.</P
><P
>If a server process does not respond to a probe, the client machine assumes that it is inaccessible. By default, the
interval between probes is three minutes, so it can take up to three minutes for a client to recognize that a server process is
once again accessible after it was inaccessible.</P
><P
>To adjust the probe interval, include the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-interval</B
></SPAN
> argument to the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs checkservers</B
></SPAN
> command while logged in as the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
>. The
new interval setting persists until you again issue the command or reboot the machine, at which time the setting returns to the
default. To preserve a nondefault setting across reboots, include the appropriate <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs
checkservers</B
></SPAN
> command in the machine's AFS initialization file.</P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_461"
>To set a client's file server probe interval</A
></H2
><OL
TYPE="1"
><LI
><P
>Become the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> on the machine, if you are not already, by issuing
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su root</B
></SPAN
>
Password: &#60;<VAR
CLASS="replaceable"
>root_password</VAR
>&#62;
</PRE
></P
></LI
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs checkservers</B
></SPAN
> command with the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-interval</B
></SPAN
> argument. <PRE
CLASS="programlisting"
>&#13; # <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs checkservers -interval</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>seconds between probes</VAR
>&#62;
</PRE
></P
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>checks</B
></SPAN
></DT
><DD
><P
>Is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>checkservers</B
></SPAN
>.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-interval</B
></SPAN
></DT
><DD
><P
>Specifies the number of seconds between probes. Provide an integer value greater than zero.</P
></DD
></DL
></DIV
></P
></LI
></OL
></DIV
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="HDRWQ411"
>Setting a Client Machine's Cell Membership</A
></H1
><P
>Each client machine belongs to a particular cell, as named in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/ThisCell</B
></SPAN
>
on its local disk. The machine's cell membership determines three defaults important to users of the machine: <UL
><LI
><P
>The cell for which users of the machine obtain tokens (authenticate) when they use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>login</B
></SPAN
> program or issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>klog</B
></SPAN
> command. There are two effects:
<UL
><LI
><P
>The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>klog</B
></SPAN
> program and AFS-modified login utilities contact an Authentication
Server in the cell named in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>ThisCell</B
></SPAN
> file.</P
></LI
><LI
><P
>The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>klog</B
></SPAN
> program and AFS-modified login utilities combine the contents of the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>ThisCell</B
></SPAN
> file with the password that the user provides, generating an encryption
key from the combination. The user's entry in the Authentication Database includes an encryption key also generated
from the combination of password and cell name. If the cell name in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>ThisCell</B
></SPAN
>
file is incorrect, users cannot authenticate even if they provide the correct password.</P
></LI
></UL
></P
></LI
><LI
><P
>The cell the Cache Manager considers its local, or home, cell. The Cache Manager allows programs from its local cell
to run with setuid permission, but not programs from foreign cells, as discussed further in <A
HREF="c21473.html#HDRWQ409"
>Determining if a Client Can Run Setuid Programs</A
>.</P
></LI
><LI
><P
>The default database server machines that are contacted by the AFS command interpreters running on this
machine.</P
></LI
></UL
></P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_463"
>To display a client machine's cell membership</A
></H2
><OL
TYPE="1"
><LI
><P
>Use a text editor or the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cat</B
></SPAN
> command to display the contents of the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/ThisCell</B
></SPAN
> file. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>cat /usr/vice/etc/ThisCell</B
></SPAN
>
</PRE
></P
></LI
></OL
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_464"
>To set a client machine's cell membership</A
></H2
><OL
TYPE="1"
><LI
><P
>Become the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> on the machine, if you are not already, by issuing
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su root</B
></SPAN
>
Password: &#60;<VAR
CLASS="replaceable"
>root_password</VAR
>&#62;
</PRE
></P
></LI
><LI
><P
>Using a text editor, replace the cell name in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/ThisCell</B
></SPAN
>
file.</P
></LI
><LI
><P
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>(Optional.)</B
></SPAN
> Reboot the machine to enable the Cache Manager to use the new cell name
immediately; the appropriate command depends on the machine's system type. The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>klog</B
></SPAN
>
program, AFS-modified login utilities, and the AFS command interpreters use the new cell name the next time they are
invoked; no reboot is necessary. <PRE
CLASS="programlisting"
>&#13; # <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>sync</B
></SPAN
>
# <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>shutdown</B
></SPAN
>
</PRE
></P
></LI
></OL
></DIV
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="HDRWQ412"
>Forcing the Update of Cached Data</A
></H1
><P
>AFS's callback mechanism normally guarantees that the Cache Manager provides the most current version of a file or
directory to the application programs running on its machine. However, you can force the Cache Manager to discard (flush) cached
data so that the next time an application program requests it, the Cache Manager fetches the latest version available at the
File Server.</P
><P
>You can control how many file system elements to flush at a time: <UL
><LI
><P
>To flush only specific files or directories, use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs flush</B
></SPAN
> command. This command
forces the Cache Manager to discard the data and status information it has cached from the specified files or directories.
It does not discard information from an application program's buffer or information that has been altered locally (changes
made in the cache but not yet saved permanently to the File Server). However, the next time an application requests the
element's data or status information, the Cache Manager has to contact the File Server to get it.</P
></LI
><LI
><P
>To flush everything cached from a certain volume, use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs flushvolume</B
></SPAN
> command.
This command works like the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs flush</B
></SPAN
> command, but differs in two ways: <UL
><LI
><P
>The Cache Manager discards data for all elements in the cache that come from the same volume as the specified
files or directories.</P
></LI
><LI
><P
>The Cache Manager discards only data, not status information. This difference has little practical effect, but
can lead to different output from the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>ls</B
></SPAN
> command when the two different commands
are used to flush the same element.</P
></LI
></UL
></P
></LI
></UL
></P
><P
>In addition to callbacks, the Cache Manager has a mechanism for tracking other kinds of possible changes, such as changes
in a volume's location. If a volume moves and the Cache Manager has not accessed any data in it for a long time, the Cache
Manager's volume location record can be wrong. To resynchronize it, use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs checkvolumes</B
></SPAN
>
command. When you issue the command, the Cache Manager creates a new table of mappings between volume names, ID numbers, and
locations. This forces the Cache Manager to reference newly relocated and renamed volumes before it can provide data from
them.</P
><P
>It is also possible for information about mount points to become corrupted in the cache. Symptoms of a corrupted mount
point included garbled output from the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs lsmount</B
></SPAN
> command, and failed attempts to change
directory to or list the contents of a mount point. Use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs flushmount</B
></SPAN
> command to discard a
corrupted mount point. The Cache Manager must refetch the mount point the next time it crosses it in a pathname. (The Cache
Manager periodically refreshes cached mount points, but the only other way to discard them immediately is to reinitialize the
Cache Manager by rebooting the machine. </P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_466"
>To flush certain files or directories</A
></H2
><OL
TYPE="1"
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs flush</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs flush</B
></SPAN
> [&#60;<VAR
CLASS="replaceable"
>dir/file path</VAR
>&#62;+]
</PRE
></P
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>flush</B
></SPAN
></DT
><DD
><P
>Must be typed in full.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>dir/file path</B
></SPAN
></DT
><DD
><P
>Names each file or directory structure to flush from the cache. Omit this argument to flush the current
working directory. Flushing a directory structure does not flush any files or subdirectories cached from
it.</P
></DD
></DL
></DIV
></P
></LI
></OL
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_467"
>To flush all data from a volume</A
></H2
><OL
TYPE="1"
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs flushvolume</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs flushvolume</B
></SPAN
> [&#60;<VAR
CLASS="replaceable"
>dir/file path</VAR
>&#62;+]
</PRE
></P
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>flushv</B
></SPAN
></DT
><DD
><P
>Is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>flushvolume</B
></SPAN
>.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>dir/file path</B
></SPAN
></DT
><DD
><P
>Names a file or directory from each volume to flush from the cache. The Cache Manager flushes everything in
the cache that it has fetched from the same volume. Omit this argument to flush all cached data fetched from the
volume that contains the current working directory.</P
></DD
></DL
></DIV
></P
></LI
></OL
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_468"
>To force the Cache Manager to notice other volume changes</A
></H2
><OL
TYPE="1"
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs checkvolumes</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs checkvolumes</B
></SPAN
>
</PRE
></P
><P
>where <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>checkv</B
></SPAN
> is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>checkvolumes</B
></SPAN
>.</P
></LI
></OL
><P
>The following command confirms that the command completed successfully:</P
><PRE
CLASS="programlisting"
>&#13; All volumeID/name mappings checked.
</PRE
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="HDRWQ413"
>To flush one or more mount points</A
></H2
><OL
TYPE="1"
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs flushmount</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs flush</B
></SPAN
> [&#60;<VAR
CLASS="replaceable"
>dir/file path</VAR
>&#62;+]
</PRE
></P
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>flushm</B
></SPAN
></DT
><DD
><P
>Is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>flushmount</B
></SPAN
>.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>dir/file path</B
></SPAN
></DT
><DD
><P
>Names each mount point to flush from the cache. Omit this argument to flush the current working directory.
Files or subdirectories cached from the associated volume are unaffected.</P
></DD
></DL
></DIV
></P
></LI
></OL
></DIV
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="HDRWQ414"
>Maintaining Server Preference Ranks</A
></H1
><P
>As mentioned in the introduction to this chapter, AFS uses client-side data caching and callbacks to reduce the amount of
network traffic in your cell. The Cache Manager also tries to make its use of the network as efficient as possible by assigning
<SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>preference ranks</I
></SPAN
> to server machines based on their network proximity to the local machine. The ranks bias
the Cache Manager to fetch information from the server machines that are on its own subnetwork or network rather than on other
networks, if possible. Reducing the network distance that data travels between client and server machine tends to reduce network
traffic and speed the Cache Manager's delivery of data to applications.</P
><P
>The Cache Manager stores two separate sets of preference ranks in kernel memory. The first set of ranks applies to
machines that run the Volume Location (VL) Server process, hereafter referred to as <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>VL Server machines</I
></SPAN
>. The
second set of ranks applies to machines that run the File Server process, hereafter referred to as <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>file server
machines</I
></SPAN
>. This section explains how the Cache Manager sets default ranks, how to use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs
setserverprefs</B
></SPAN
> command to change the defaults or set new ranks, and how to use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs
getserverprefs</B
></SPAN
> command to display the current set of ranks.</P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_471"
>How the Cache Manager Sets Default Ranks</A
></H2
><P
>As the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsd</B
></SPAN
> program initializes the Cache Manager, it assigns a preference rank of
10,000 to each of the VL Server machines listed in the local <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/CellServDB</B
></SPAN
> file.
It then randomizes the ranks by adding an integer randomly chosen from the range 0 (zero) to 126. It avoids assigning the same
rank to machines in one cell, but it is possible for machines from different cells to have the same rank. This does not
present a problem in use, because the Cache Manager compares the ranks of only one cell's database server machines at a time.
Although AFS supports the use of multihomed database server machines, the Cache Manager only uses the single address listed
for each database server machine in the local <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/CellServDB</B
></SPAN
> file. Only Ubik can
take advantage of a multihomed database server machine's multiple interfaces.</P
><P
>The Cache Manager assigns preference ranks to a file server machine when it obtains the server's VLDB record from the VL
Server, the first time that it accesses a volume that resides on the machine. If the machine is multihomed, the Cache Manager
assigns a distinct rank to each of its interfaces (up to the number of interfaces that the VLDB can store for each machine,
which is specified in the <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>IBM AFS Release Notes</I
></SPAN
>). The Cache Manager compares the interface's IP address
to the local machine's address and applies the following algorithm: <UL
><LI
><P
>If the local machine is a file server machine, the base rank for each of its interfaces is 5,000.</P
></LI
><LI
><P
>If the file server machine interface is on the same subnetwork as the local machine, its base rank is
20,000.</P
></LI
><LI
><P
>If the file server machine interface is on the same network as the local machine, or is at the distant end of a
point-to-point link with the local machine, its base rank is 30,000.</P
></LI
><LI
><P
>If the file server machine interface is on a different network than the local machine, or the Cache Manager cannot
obtain network information about it, its base rank is 40,000.</P
></LI
></UL
></P
><P
>If the client machine has only one interface, the Cache Manager compares it to the server interface's IP address and
sets a rank according to the algorithm. If the client machine is multihomed, the Cache Manager compares each of the local
interface addresses to the server interface, and assigns to the server interface the lowest rank that results from comparing
it to all of the client interfaces.</P
><P
>After assigning a base rank to a file server machine interface, the Cache Manager adds to it a number randomly chosen
from the range 0 (zero) to 15. As an example, a file server machine interface in the same subnetwork as the local machine
receives a base rank of 20,000, but the Cache Manager records the actual rank as an integer between 20,000 and 20,015. This
process reduces the number of interfaces that have exactly the same rank. As with VL Server machine ranks, it is possible for
file server machine interfaces from foreign cells to have the same rank as interfaces in the local cell, but this does not
present a problem. Only the relative ranks of the interfaces that house a specific volume are relevant, and AFS supports
storage of a volume in only one cell at a time.</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_472"
>How the Cache Manager Uses Preference Ranks</A
></H2
><P
>Each preference rank pairs an interface's IP address with an integer that can range from 1 to 65,534. A lower rank
(lower number) indicates a stronger preference. Once set, a rank persists until the machine reboots, or until you use the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setserverprefs</B
></SPAN
> command to change it.</P
><P
>The Cache Manager uses VL Server machine ranks when it needs to fetch volume location information from a cell. It
compares the ranks for the cell's VL Server machines and attempts to contact the VL Server process on the machine with the
best (lowest integer) rank. If it cannot reach that VL Server, it tries to contact the VL Server with the next best rank, and
so on. If all of a cell's VL Server machines are inaccessible, the Cache Manager cannot fetch data from the cell.</P
><P
>Similarly, when the Cache Manager needs to fetch data from a volume, it compares the ranks for the interfaces of
machines that house the volume, and attempts to contact the interface that has the best rank. If it cannot reach the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fileserver</B
></SPAN
> process via that interface, it tries to contact the interface with the next best integer
rank, and so on. If it cannot reach any of the interfaces for machines that house the volume, it cannot fetch data from the
volume.</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_473"
>Displaying and Setting Preference Ranks</A
></H2
><P
>To display the file server machine ranks that the Cache Manager is using, use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs
getserverprefs</B
></SPAN
> command. Include the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-vlservers</B
></SPAN
> flag to display VL Server machine
ranks instead. By default, the output appears on the standard output stream (stdout), but you can write it to a file instead
by including the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-file</B
></SPAN
> argument.</P
><P
>The Cache Manager stores IP addresses rather than hostnames in its kernel list of ranks, but by default the output
identifies interfaces by hostname after calling a translation routine that refers to either the cell's name service (such as
the Domain Name Server) or the local host table. If an IP address appears in this case, it is because the translation attempt
failed. To bypass the translation step and display IP addresses rather than hostnames, include the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-numeric</B
></SPAN
> flag. This can significantly speed up the output.</P
><P
>You can use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setserverprefs</B
></SPAN
> command to reset an existing preference rank, or to
set the initial rank of a file server machine interface or VL Server machine for which the Cache Manager has no rank. The
ranks you set persist until the machine reboots or until you issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setserverprefs</B
></SPAN
>
command again. To make a rank persist across a reboot, place the appropriate <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs
setserverprefs</B
></SPAN
> command in the machine's AFS initialization file.</P
><P
>As with default ranks, the Cache Manager adds a randomly chosen integer to each rank range that you assign. For file
server machine interfaces, the randomizing number is from the range 0 (zero) to 15; for VL Server machines, it is from the
range 0 (zero) to 126. For example, if you assign a rank of 15,000 to a file server machine interface, the Cache Manager
stores an integer between 15,000 to 15,015.</P
><P
>To assign VL Server machine ranks, list them after the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-vlserver</B
></SPAN
> argument to the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setserverprefs</B
></SPAN
> command.</P
><P
>To assign file server machine ranks, use or more of the three possible methods: <OL
TYPE="1"
><LI
><P
>List them after the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-servers</B
></SPAN
> argument on the command line.</P
></LI
><LI
><P
>Record them in a file and name it with the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-file</B
></SPAN
> argument. You can easily
generate a file with the proper format by including the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-file</B
></SPAN
> argument to the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getserverprefs</B
></SPAN
> command.</P
></LI
><LI
><P
>Provide them via the standard input stream, by including the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-stdin</B
></SPAN
> flag. This
enables you to feed in values directly from a command or script that generates preferences using an algorithm
appropriate for your cell. It must generate them in the proper format, with one or more spaces between each pair and
between the two parts of the pair. The AFS distribution does not include such a script, so you must write one if you
want to use this method.</P
></LI
></OL
></P
><P
>You can combine any of the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-servers</B
></SPAN
>, <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-file</B
></SPAN
>, and
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-stdin</B
></SPAN
> options on the same command line if you wish. If more than one of them specifies a
rank for the same interface, the one assigned with the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-servers</B
></SPAN
> argument takes precedence.
You can also provide the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-vlservers</B
></SPAN
> argument on the same command line to set VL Server
machine ranks at the same time as file server machine ranks.</P
><P
>The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs</B
></SPAN
> command interpreter does not verify hostnames or IP addresses, and so willingly
stores ranks for hostnames and addresses that don't actually exist. The Cache Manager never uses such ranks unless the same
VLDB record for a server machine records the same incorrect information. </P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_474"
>To display server preference ranks</A
></H2
><OL
TYPE="1"
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getserverprefs</B
></SPAN
> command to display the Cache Manager's preference ranks
for file server machines or VL Server machines. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getserverprefs</B
></SPAN
> [<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-file</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>output to named file</VAR
>&#62;] [<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-numeric</B
></SPAN
>] [<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-vlservers</B
></SPAN
>]
</PRE
></P
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>gp</B
></SPAN
></DT
><DD
><P
>Is an acceptable alias for <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>getserverprefs</B
></SPAN
> (<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>gets</B
></SPAN
> is the shortest acceptable abbreviation).</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-file</B
></SPAN
></DT
><DD
><P
>Specifies the pathname of the file to which to write the list of ranks. Omit this argument to display the
list on the standard output stream (stdout).</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-numeric</B
></SPAN
></DT
><DD
><P
>Displays the IP address, rather than the hostname, of each ranked machine interface. Omit this flag to have
the addresses translated into hostnames, which takes longer.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-vlservers</B
></SPAN
></DT
><DD
><P
>Displays ranks for VL Server machines rather than file server machines.</P
></DD
></DL
></DIV
></P
><P
>The following example displays file server machine ranks. The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-numeric</B
></SPAN
> flag is not
used, so the appearance of an IP address indicates that is not currently possible to translate it to a hostname.</P
><PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs gp</B
></SPAN
>
fs5.abc.com 20000
fs1.abc.com 30014
server1.stateu.edu 40011
fs3.abc.com 20001
fs4.abc.com 30001
192.12.106.120 40002
192.12.106.119 40001
. . . . . . .
</PRE
></LI
></OL
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_475"
>To set server preference ranks</A
></H2
><OL
TYPE="1"
><LI
><P
>Become the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> on the machine, if you are not already, by issuing
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su root</B
></SPAN
>
Password: &#60;<VAR
CLASS="replaceable"
>root_password</VAR
>&#62;
</PRE
></P
></LI
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setserverprefs</B
></SPAN
> command to set the Cache Manager's preference ranks for
one or more file server machines or VL Server machines. <PRE
CLASS="programlisting"
>&#13; # <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setserverprefs</B
></SPAN
> [<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-servers</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>fileserver names and ranks</VAR
>&#62;+] \
[<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-vlservers</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>VL server names and ranks</VAR
>&#62;+] \
[<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-file</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>input from named file</VAR
>&#62;] [<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-stdin</B
></SPAN
>]
</PRE
></P
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>sp</B
></SPAN
></DT
><DD
><P
>Is an acceptable alias for <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>setserverprefs</B
></SPAN
> (<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>sets</B
></SPAN
> is the shortest acceptable abbreviation).</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-servers</B
></SPAN
></DT
><DD
><P
>Specifies one or more pairs of file server machine interface and rank. Identify each interface by its
fully-qualified hostname or IP address in dotted decimal format. Acceptable ranks are the integers from <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>1</B
></SPAN
> to <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>65534</B
></SPAN
>. Separate the parts of a pair, and the pairs
from one another, with one or more spaces.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-vlservers</B
></SPAN
></DT
><DD
><P
>Specifies one or more pairs of VL Server machine and rank. Identify each machine by its fully-qualified
hostname or IP address in dotted decimal format. Acceptable ranks are the integers from <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>1</B
></SPAN
> to <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>65534</B
></SPAN
>.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-file</B
></SPAN
></DT
><DD
><P
>Specifies the pathname of a file that contains one more pairs of file server machine interface and rank.
Place each pair on its own line in the file. Use the same format for interfaces and ranks as with the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-servers</B
></SPAN
> argument.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-stdin</B
></SPAN
></DT
><DD
><P
>Indicates that pairs of file server machine interface and rank are being provided via the standard input
stream (stdin). The program or script that generates the pairs must format them in the same manner as for the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-servers</B
></SPAN
> argument.</P
></DD
></DL
></DIV
></P
></LI
></OL
></DIV
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="HDRWQ415"
>Managing Multihomed Client Machines</A
></H1
><P
>The File Server can choose the interface to which to send a message when it initiates communication with the Cache Manager
on a multihomed client machine (one with more than one network interface and IP address). If that interface is inaccessible, it
automatically switches to an alternate. This improves AFS performance, because it means that the outage of an interface does not
interrupt communication between File Server and Cache Manager.</P
><P
>The File Server can choose the client interface when it sends two types of messages: <UL
><LI
><P
>A message to break the callback that the Cache Manager holds on a cached file</P
></LI
><LI
><P
>A <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>ping</I
></SPAN
> message to check that the Cache Manager is still accessible and responding; the File
Server sends such a message every few minutes</P
></LI
></UL
></P
><P
>(The File Server does not choose which client interface to respond to when filling a Cache Manager's request for AFS data.
In that case, it always responds to the client interface via which the Cache Manager sent the request.)</P
><P
>The Cache Manager compiles the list of eligible interfaces on its client machine automatically as it initializes, and
records them in kernel memory. When the Cache Manager first establishes a connection with the File Server, it sends along the
list of interface addresses. The File Server records the addresses, and uses the one at the top of the list when it needs to
break a callback or send a ping to the Cache Manager. If that interface is inaccessible, the File Server simultaneously sends a
message to all of the other interfaces in the list. Whichever interface replies first is the one to which the File Server sends
future messages.</P
><P
>You can control which addresses the Cache Manager registers with File Servers by listing them in two files in the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc</B
></SPAN
> directory on the client machine's local disk: <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>NetInfo</B
></SPAN
> and <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>NetRestrict</B
></SPAN
>. If the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>NetInfo</B
></SPAN
>
file exists when the Cache Manager initializes, the Cache Manager uses its contents as the basis for the list of interfaces.
Otherwise, the Cache Manager uses the list of interfaces configured with the operating system. It then removes from the list any
addresses that appear in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/NetRestrict</B
></SPAN
> file, if it exists. The Cache Manager
records the resulting list in kernel memory.</P
><P
>You can also use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setclientaddrs</B
></SPAN
> command to change the list of addresses stored in
the Cache Manager's kernel memory, without rebooting the client machine. The list of addresses you provide on the command line
completely replaces the current list in kernel memory. The changes you make persist only until the client machine reboots,
however. To preserve the revised list across reboots, list the interfaces in the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>NetInfo</B
></SPAN
> file
(and if appropriate, the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>NetRestrict</B
></SPAN
> file) in the local <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc</B
></SPAN
> directory. (You can also place the appropriate <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs
setclientaddrs</B
></SPAN
> command in the machine's AFS initialization script, but that is less efficient: by the time the Cache
Manager reads the command in the script, it has already compiled a list of interfaces.)</P
><P
>To display the list of addresses that the Cache Manager is currently registering with File Servers, use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getclientaddrs</B
></SPAN
> command.</P
><P
>Keep the following in mind when you change the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>NetInfo</B
></SPAN
> or <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>NetRestrict</B
></SPAN
> file, or issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getclientaddrs</B
></SPAN
> or <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setclientaddrs</B
></SPAN
> commands: <UL
><LI
><P
>When you issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setclientaddrs</B
></SPAN
> command, the revised list of addresses does
not propagate automatically to File Servers with which the Cache Manager has already established a connection. They
continue to use the list that the Cache Manager registered with them when it first established a connection. To force
previously contacted File Servers to use the revised list, you must either reboot each file server machine, or reboot the
client machine after changing its <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>NetInfo</B
></SPAN
> file, <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>NetRestrict</B
></SPAN
> file, or both.</P
></LI
><LI
><P
>The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs</B
></SPAN
> command interpreter verifies that each of the addresses you specify on the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setclientaddrs</B
></SPAN
> command line is actually configured with the client machine's operating
system. If it is not, the command fails with an error message that marks the address as a <SAMP
CLASS="computeroutput"
>Nonexistent
interface</SAMP
>.</P
></LI
><LI
><P
>As previously noted, the File Server does not use the registered list of addresses when it responds to the Cache
Manager's request for data (as opposed to initiating communication itself). It always attempts to send its reply to the
interface from which the Cache Manager sent the request. If the reply attempt fails, the File Server selects an alternate
route for resending the reply according to its server machine's network routing configuration, not the list of addresses
registered by the Cache Manager.</P
></LI
><LI
><P
>The Cache Manager does not use the list of interfaces when choosing the interface via which to establish a
connection to a File Server.</P
></LI
><LI
><P
>The list of addresses that the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getclientaddrs</B
></SPAN
> command displays is not
necessarily the one that a specific File Server is using, if an administrator has issued the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs
setclientaddrs</B
></SPAN
> command since the Cache Manager first contacted that File Server. It determines only which
addresses the Cache Manager registers when connecting to File Servers in future.</P
></LI
></UL
></P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_477"
>To create or edit the client NetInfo file</A
></H2
><OL
TYPE="1"
><LI
><P
>Become the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> on the machine, if you are not already, by issuing
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su root</B
></SPAN
>
Password: &#60;<VAR
CLASS="replaceable"
>root_password</VAR
>&#62;
</PRE
></P
></LI
><LI
><P
>Using a text editor, open the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/NetInfo</B
></SPAN
> file. Place one IP address in
dotted decimal format (for example, <SAMP
CLASS="computeroutput"
>192.12.107.33</SAMP
>) on each line. On the first line, put
the address that you want each File Server to use initially. The order of the remaining machines does not matter, because
if an RPC to the first interface fails, the File Server simultaneously sends RPCs to all of the other interfaces in the
list. Whichever interface replies first is the one to which the File Server then sends pings and RPCs to break
callbacks.</P
></LI
><LI
><P
>If you want the Cache Manager to start using the revised list immediately, either reboot the machine, or use the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setclientaddrs</B
></SPAN
> command to create the same list of addresses in kernel memory
directly.</P
></LI
></OL
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_478"
>To create or edit the client NetRestrict file</A
></H2
><OL
TYPE="1"
><LI
><P
>Become the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> on the machine, if you are not already, by issuing
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su root</B
></SPAN
>
Password: &#60;<VAR
CLASS="replaceable"
>root_password</VAR
>&#62;
</PRE
></P
></LI
><LI
><P
>Using a text editor, open the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>/usr/vice/etc/NetRestrict</B
></SPAN
> file. Place one IP address
in dotted decimal format on each line. The order of the addresses is not significant. Use the value <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>255</B
></SPAN
> as a wildcard that represents all possible addresses in that field. For example, the entry
<SAMP
CLASS="computeroutput"
>192.12.105.255</SAMP
> indicates that the Cache Manager does not register any of the addresses in
the 192.12.105 subnet.</P
></LI
><LI
><P
>If you want the Cache Manager to start using the revised list immediately, either reboot the machine, or use the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setclientaddrs</B
></SPAN
> command to set a list of addresses that does not included the
prohibited ones.</P
></LI
></OL
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_479"
>To display the list of addresses from kernel memory</A
></H2
><OL
TYPE="1"
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getclientaddrs</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs getclientaddrs</B
></SPAN
>
</PRE
></P
><P
>where <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>gc</B
></SPAN
> is an acceptable alias for <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>getclientaddrs</B
></SPAN
>
(<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>getcl</B
></SPAN
> is the shortest acceptable abbreviation).</P
></LI
></OL
><P
>The output lists each IP address on its own line, in dotted decimal format. </P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_480"
>To set the list of addresses in kernel memory</A
></H2
><OL
TYPE="1"
><LI
><P
>Become the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> on the machine, if you are not already, by issuing
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su root</B
></SPAN
>
Password: &#60;<VAR
CLASS="replaceable"
>root_password</VAR
>&#62;
</PRE
></P
></LI
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setclientaddrs</B
></SPAN
> command to replace the list of addresses currently in
kernel memory with a new list. <PRE
CLASS="programlisting"
>&#13; # <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs setclientaddrs</B
></SPAN
> [<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-address</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>client network interfaces</VAR
>&#62;+]
</PRE
></P
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>sc</B
></SPAN
></DT
><DD
><P
>Is an acceptable alias for <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>setclientaddrs</B
></SPAN
> (<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>setcl</B
></SPAN
> is the shortest acceptable abbreviation).</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-address</B
></SPAN
></DT
><DD
><P
>Specifies one or more IP addresses in dotted decimal format (hostnames are not acceptable). Separate each
address with one or more spaces.</P
></DD
></DL
></DIV
></P
></LI
></OL
></DIV
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="HDRWQ416"
>Controlling the Display of Warning and Informational Messages</A
></H1
><P
>By default, the Cache Manager generates two types of warning and informational messages: <UL
><LI
><P
>It sends <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>user messages</I
></SPAN
>, which provide user-level status and warning information, to user
screens.</P
></LI
><LI
><P
>It sends <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>console messages</I
></SPAN
>, which provide system-level status and warning information, to the
client machine's designated console.</P
></LI
></UL
></P
><P
>You can use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs messages</B
></SPAN
> command to control whether the Cache Manager displays either
type of message, both types, or neither. It is best not to disable messages completely, because they provide useful
information.</P
><P
>If you want to monitor Cache Manager status and performance more actively, you can use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>afsmonitor</B
></SPAN
> program to collect an extensive set of statistics (it also gathers File Server statistics). If
you experience performance problems, you can use <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fstrace</B
></SPAN
> suite of commands to gather a
low-level trace of Cache Manager operations, which the AFS Support and Development groups can analyze to help solve your
problem. To learn about both utilities, see <A
HREF="c18360.html"
>Monitoring and Auditing AFS Performance</A
>. </P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_482"
>To control the display of warning and status messages</A
></H2
><OL
TYPE="1"
><LI
><P
>Become the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> on the machine, if you are not already, by issuing
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su root</B
></SPAN
>
Password: &#60;<VAR
CLASS="replaceable"
>root_password</VAR
>&#62;
</PRE
></P
></LI
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs messages</B
></SPAN
> command, using the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-show</B
></SPAN
>
argument to specify the type of messages to be displayed. <PRE
CLASS="programlisting"
>&#13; # <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs messages -show</B
></SPAN
> &#60;<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>user</B
></SPAN
>|<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>console</B
></SPAN
>|<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>all</B
></SPAN
>|<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>none</B
></SPAN
>&#62;
</PRE
></P
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>me</B
></SPAN
></DT
><DD
><P
>Is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>messages</B
></SPAN
>.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-show</B
></SPAN
></DT
><DD
><P
>Specifies the types of messages to display. Choose one of the following values: <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>user</B
></SPAN
></DT
><DD
><P
>Sends user messages to user screens.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>console</B
></SPAN
></DT
><DD
><P
>Sends console messages to the console.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>all</B
></SPAN
></DT
><DD
><P
>Sends user messages to user screens and console messages to the console (the default if the
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-show</B
></SPAN
> argument is omitted).</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>none</B
></SPAN
></DT
><DD
><P
>Disables messages completely.</P
></DD
></DL
></DIV
></P
></DD
></DL
></DIV
></P
></LI
></OL
></DIV
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="HDRWQ417"
>Displaying and Setting the System Type Name</A
></H1
><P
>The Cache Manager stores the system type name of the local client machine in kernel memory. It reads in the default value
from a hardcoded definition in the AFS client software.</P
><P
>The Cache Manager uses the system name as a substitute for the @sys variable in AFS pathnames. The variable is useful when
creating a symbolic link from the local disk to an AFS directory that houses binaries for the client machine's system type.
Because the @sys variable automatically steers the Cache Manager to the appropriate directory, you can create the same symbolic
link on client machines of different system types. (You can even automate the creation operation by using the package utility
described in <A
HREF="c23832.html"
>Configuring Client Machines with the package Program</A
>.) The link also remains valid
when you upgrade the machine to a new system type.</P
><P
>Configuration is simplest if you use the system type names that AFS assigns. For a list, see the <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>IBM AFS Release
Notes</I
></SPAN
>.</P
><P
>To display the system name stored in kernel memory, use the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>sys</B
></SPAN
> or <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs sysname</B
></SPAN
> command. To change the name, add the latter command's <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-newsys</B
></SPAN
>
argument. </P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_484"
>To display the system type name</A
></H2
><OL
TYPE="1"
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs sysname</B
></SPAN
> or <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>sys</B
></SPAN
> command.
<PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs sysname</B
></SPAN
>
% <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>sys</B
></SPAN
>
</PRE
></P
></LI
></OL
><P
>The output of the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs sysname</B
></SPAN
> command has the following format:</P
><PRE
CLASS="programlisting"
>&#13; Current sysname is 'system_name'
</PRE
><P
>The <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>sys</B
></SPAN
> command displays the system_name string with no other text.</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_485"
>To change the system type name</A
></H2
><OL
TYPE="1"
><LI
><P
>Become the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> on the machine, if you are not already, by issuing
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su root</B
></SPAN
>
Password: &#60;<VAR
CLASS="replaceable"
>root_password</VAR
>&#62;
</PRE
></P
></LI
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs sysname</B
></SPAN
> command, using the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-newsys</B
></SPAN
>
argument to specify the new name. <PRE
CLASS="programlisting"
>&#13; # <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs sysname</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>new sysname</VAR
>&#62;
</PRE
></P
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>sys</B
></SPAN
></DT
><DD
><P
>Is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>sysname</B
></SPAN
>.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>new sysname</B
></SPAN
></DT
><DD
><P
>Specifies the new system type name.</P
></DD
></DL
></DIV
></P
></LI
></OL
></DIV
></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="HDRWQ418"
>Enabling Asynchronous Writes</A
></H1
><P
>By default, the Cache Manager writes all data to the File Server immediately and synchronously when an application program
closes a file. That is, the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>close</B
></SPAN
> system call does not return until the Cache Manager has
actually written all of the cached data from the file back to the File Server. You can enable the Cache Manager to write files
asynchronously by specifying the number of kilobytes of a file that can remain to be written to the File Server when the Cache
Manager returns control to the application.</P
><P
>Enabling asynchronous writes can be helpful to users who commonly work with very large files, because it usually means
that the application appears to perform faster. However, it introduces some complications. It is best not to enable asynchronous
writes unless the machine's users are sophisticated enough to understand the potential problems and how to avoid them. The
complications include the following: <UL
><LI
><P
>In most cases, the Cache Manager returns control to applications earlier than it does by default, but it is not
guaranteed to do so. Users cannot always expect faster performance.</P
></LI
><LI
><P
>If an asynchronous write fails, there is no way to notify the application, because the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>close</B
></SPAN
> system call has already returned with a code indicating success.</P
></LI
><LI
><P
>Asynchronous writing increases the possibility that the user fails to notice when a write operation makes a volume
exceed its quota. As always, the portion of the file that exceeds the quota is lost, as indicated by a message like the
following: <PRE
CLASS="programlisting"
>&#13; No space left on device
</PRE
></P
><P
>To avoid losing data because of insufficient quota, before closing a file users must verify that the volume housing
the file has enough free space to accommodate it.</P
></LI
></UL
></P
><P
>When you enable asynchronous writes by issuing the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs storebehind</B
></SPAN
> command, you set the
number of kilobytes of a file that can still remain to be written to the File Server when the Cache Manager returns control to
the application program. You can apply the setting either to all files manipulated by applications running on the machine, or
only to certain files: <UL
><LI
><P
>The setting that applies to all files is called the <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>default store asynchrony</I
></SPAN
> for the machine,
and persists until the machine reboots. If, for example, you set the default store asynchrony to 10 KB, it means that when
an application closes a file, the Cache Manager can return control to the application as soon as no more than 10 KB of a
file that the application has closed remain to be written to the File Server.</P
></LI
><LI
><P
>The setting for an individual file overrides the default store asynchrony and persists as long as there is an entry
for the file in the internal table that the Cache Manager uses to track information about files. In general, such an entry
persists at least until an application closes the file or exits completely, but the Cache Manager is free to recycle the
entry if the file is inactive and it needs to free up slots in the table. To be sure the entry exists in the table, issue
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs storebehind</B
></SPAN
> command shortly before closing the file.</P
></LI
></UL
></P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_487"
>To set the default store asynchrony</A
></H2
><OL
TYPE="1"
><LI
><P
>Become the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> on the machine, if you are not already, by issuing
the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su</B
></SPAN
> command. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su root</B
></SPAN
>
Password: &#60;<VAR
CLASS="replaceable"
>root_password</VAR
>&#62;
</PRE
></P
></LI
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs storebehind</B
></SPAN
> command with the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-allfiles</B
></SPAN
> argument. <PRE
CLASS="programlisting"
>&#13; # <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs storebehind -allfiles</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>new default (KB)</VAR
>&#62; [<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-verbose</B
></SPAN
>]
</PRE
></P
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>st</B
></SPAN
></DT
><DD
><P
>Is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>storebehind</B
></SPAN
>.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-allfiles</B
></SPAN
></DT
><DD
><P
>Sets the number of kilobytes of data that can remain to be written to the File Server when the Cache Manager
returns control to the application that closed a file.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-verbose</B
></SPAN
></DT
><DD
><P
>Produces a message that confirms the new setting.</P
></DD
></DL
></DIV
></P
></LI
></OL
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_488"
>To set the store asynchrony for one or more files</A
></H2
><OL
TYPE="1"
><LI
><P
>Verify that you have the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>w</B
></SPAN
> (<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>write</B
></SPAN
>) permission on
the access control list (ACL) of each file for which you are setting the store asynchrony, by issuing the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs listacl</B
></SPAN
> command, which is described fully in <A
HREF="c31274.html#HDRWQ572"
>Displaying ACLs</A
>.
<PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs listacl</B
></SPAN
> dir/file path
</PRE
></P
><P
>Alternatively, become the local superuser <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>root</B
></SPAN
> on the client machine, if you are
not already, by issuing the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su</B
></SPAN
> command.</P
><PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>su root</B
></SPAN
>
Password: &#60;<VAR
CLASS="replaceable"
>root_password</VAR
>&#62;
</PRE
></LI
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs storebehind</B
></SPAN
> command with the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-kbytes</B
></SPAN
>
and <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-files</B
></SPAN
> arguments. <PRE
CLASS="programlisting"
>&#13; # <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs storebehind -kbytes</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>asynchrony for specified names</VAR
>&#62; \
<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-files</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>specific pathnames</VAR
>&#62;+ \
[<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-verbose</B
></SPAN
>]
</PRE
></P
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>st</B
></SPAN
></DT
><DD
><P
>Is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>storebehind</B
></SPAN
>.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-kbytes</B
></SPAN
></DT
><DD
><P
>Sets the number of kilobytes of data that can remain to be written to the File Server when the Cache Manager
returns control to the application that closed a file named by the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-files</B
></SPAN
>
argument.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-files</B
></SPAN
></DT
><DD
><P
>Specifies each file for which to set a store asynchrony that overrides the default. Partial pathnames are
interpreted relative to the current working directory.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-verbose</B
></SPAN
></DT
><DD
><P
>Produces a message that confirms that new setting.</P
></DD
></DL
></DIV
></P
></LI
></OL
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_489"
>To display the default store asynchrony</A
></H2
><OL
TYPE="1"
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs storebehind</B
></SPAN
> command with no arguments, or with the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-verbose</B
></SPAN
> flag only. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs storebehind</B
></SPAN
> [<SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-verbose</B
></SPAN
>]
</PRE
></P
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>st</B
></SPAN
></DT
><DD
><P
>Is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>storebehind</B
></SPAN
>.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-verbose</B
></SPAN
></DT
><DD
><P
>Produces output that reports the default store asynchrony.</P
></DD
></DL
></DIV
></P
></LI
></OL
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="Header_490"
>To display the store asynchrony for one or more files</A
></H2
><OL
TYPE="1"
><LI
><P
>Issue the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs storebehind</B
></SPAN
> command with the <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-files</B
></SPAN
>
argument only. <PRE
CLASS="programlisting"
>&#13; % <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>fs storebehind</B
></SPAN
> <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-files</B
></SPAN
> &#60;<VAR
CLASS="replaceable"
>specific pathnames</VAR
>&#62;+
</PRE
></P
><P
>where <DIV
CLASS="variablelist"
><DL
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>st</B
></SPAN
></DT
><DD
><P
>Is the shortest acceptable abbreviation of <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>storebehind</B
></SPAN
>.</P
></DD
><DT
><SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-files</B
></SPAN
></DT
><DD
><P
>Specifies each file for which to display the store asynchrony. Partial pathnames are interpreted relative to
the current working directory.</P
></DD
></DL
></DIV
></P
></LI
></OL
><P
>The output lists each file separately. If a value has previously been set for the specified files, the output reports
the following:</P
><PRE
CLASS="programlisting"
>&#13; Will store up to y kbytes of file asynchronously.
Default store asynchrony is x kbytes.
</PRE
><P
>If the default store asynchrony applies to a file (because you have not set a <SPAN
CLASS="bold"
><B
CLASS="emphasis"
>-kbytes</B
></SPAN
>
value for it), the output reports the following:</P
><PRE
CLASS="programlisting"
>&#13; Will store file according to default.
Default store asynchrony is x kbytes.
</PRE
></DIV
></DIV
></DIV
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