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LICENSE IPL10 Document linked cells and non-voting replicas in the CellServDB man page and note the need for better linked cell documentation.
233 lines
8.7 KiB
Plaintext
233 lines
8.7 KiB
Plaintext
=head1 NAME
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CellServDB - Lists the database server machines in AFS cells
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=head1 DESCRIPTION
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There are two versions of the F<CellServDB> file, both of which have the
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same format. One version is used by an AFS client and lists all of the
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database server machines in the local cell and any foreign cell that is to
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be accessible from the local client machine. The other version is used on
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servers and need list only the database servers in the local cell; in some
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configurations it can be a link to the same file the client uses.
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=head2 Client CellServDB
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Along with AFSDB entries in DNS, the client version of the CellServDB file
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lists the database server machines in the local cell and any foreign cell
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that is to be accessible from the local client machine. Database server
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machines run the Authentication Server (optional), Backup Server
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(optional), Protection Server, and Volume Location (VL) Server (the
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B<kaserver>, B<buserver>, B<ptserver>, and B<vlserver>) processes, which
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maintain the cell's administrative AFS databases.
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The Cache Manager and other processes running on a client machine use the
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list of a cell's database server machines when performing several common
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functions, including:
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=over 4
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=item *
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Fetching files. The Cache Manager contacts the VL Server to learn
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the location of the volume containing a requested file or directory.
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=item *
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Creating, viewing, and manipulating protection groups. The B<pts> command
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interpreter contacts the Protection Server when users create protection
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groups or request information from the Protection Database.
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=item *
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Populating the contents of the fake F<root.afs> volume mounted at F</afs>
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(or the alternative mount point specified in F<cacheinfo>) when B<afsd> is
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run in C<-dynroot> mode. The default contents of this directory will
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match the cells listed in the client F<CellServDB> file.
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=item *
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Authenticating users. Client-side authentication programs (such as an
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AFS-modified login utility or the B<klog> command interpreter) contact the
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Authentication Server to obtain a server ticket, which the AFS server
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processes accept as proof that the user is authenticated. This only
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applies to AFS cells using the deprecated Authentication Server instead of
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Kerberos v5 and B<aklog>.
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=back
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The Cache Manager reads the CellServDB file into kernel memory as it
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initializes, and not again until the machine next reboots or the client
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service restarts. To enable users on the local machine to continue
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accessing the cell correctly, update the file whenever a database server
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machine is added to or removed from a cell. To update the kernel-resident
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list of database server machines without rebooting, use the B<fs newcell>
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command.
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If the client attempts to access an AFS cell not listed in F<CellServDB>
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and B<afsd> was started with the B<-afsdb> option, the Cache Manager will
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attempt an AFSDB DNS record lookup and dynamically add the database server
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locations for that cell based on the result of the DNS query. If the
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B<-afsdb> option was not used, all AFS cells that will be accessed by a
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client machine must either be listed in F<CellServDB> or added with the
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B<fs newcell> command.
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The F<CellServDB> file is in ASCII format and must reside in the
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F</usr/vice/etc> directory on each AFS client machine. Use a text editor
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to create and maintain it.
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The client version of the F<CellServDB> file is distinct from the server
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version, which resides in the F</usr/afs/etc> directory on each AFS server
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machine. The client version lists the database server machines in every
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AFS cell that the cell administrator wants the machine's users to be able
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to access, whereas the server version lists only the local cell's database
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server machines.
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=head2 Server CellServDB
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The server version of the F<CellServDB> file lists the local cell's
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database server machines. These machines run the Authentication Server
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(optional), Backup Server (optional), Protection Server, and Volume
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Location (VL) Server (the B<kaserver>, B<buserver>, B<ptserver>, and
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B<vlserver>) processes, which maintain the cell's administrative AFS
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databases. The initial version of the file is created with the B<bos
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setcellname> command during the installation of the cell's server machine,
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which is automatically recorded as the cell's first database server
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machine. When adding or removing database server machines, be sure to
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update this file appropriately. It must reside in the F</usr/afs/etc>
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directory on each AFS server machine. The database server processes,
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in addition to the usual configuration allowing each to be elected
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synchronization site and coordinate updates, can be set up as readonly
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database clone servers. Such servers can never be elected as the
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synchronization site.
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The database server processes consult the F<CellServDB> file to learn
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about their peers, with which they must maintain constant connections in
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order to coordinate replication of changes across the multiple copies of
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each database. The other AFS server processes consult the file to learn
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which machines to contact for information from the databases when they
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need it.
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Although the server F<CellServDB> file is in ASCII format, do not use a
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text editor to alter it. Instead always use the appropriate commands from
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the B<bos> command suite:
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=over 4
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=item *
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The B<bos addhost> command to add a machine to the file.
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=item *
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The B<bos listhosts> command to display the list of machines from the
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file.
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=item *
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The B<bos removehost> command to remove a machine from the file.
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=back
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In cells that use the Update Server to distribute the contents of the
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F</usr/afs/etc> directory, it is customary to edit only the copy of the
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file stored on the system control machine. Otherwise, edit the file on
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each server machine individually. For instructions on adding and removing
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database server machine, see the I<OpenAFS Quick Start> chapter on
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installing additional server machines. Updates to the server F<CellServDB>
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will trigger reloading the cell server configurations automatically in the
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AFS server processes.
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=head2 CellServDB Format
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Both F<CellServDB> files have the same format:
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=over 4
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=item *
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The first line begins at the left margin with the greater-than character
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(C<< > >>), followed immediately by the cell's name without an intervening
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space. Optionally, a comment can follow any number of spaces and a octothorpe
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(C<#>), perhaps to identify the organization associated with the
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cell. A variant of this allows the defintion of a linked cell: after the
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leading (C<< > >>) and cell name, a space and a second cell name may be
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listed before the optional spaces, octothorpe and comment.
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=item *
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Each subsequent line in the entry identifies one of the cell's database
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server machines, with the indicated information in order:
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=over 4
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=item *
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The database server machine's IP address in dotted-decimal format, optionally
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enclosed in square braces (C<< [ >>)(C<< ] >>) to define a non-voting clone.
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=item *
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One or more spaces.
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=item *
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An octothorpe (#), followed by the machine's fully qualified hostname
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without an intervening space. This number sign does not indicate that the
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hostname is a comment. It is a required field.
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=back
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=back
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No extra blank lines or newline characters are allowed in the file, even
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after the last entry. Their presence can prevent the Cache Manager from
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reading the file into kernel memory, resulting in an error message.
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grand.central.org maintains a list of the database server machines in all
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cells that have registered themselves as receptive to access from foreign
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cells. When a cell's administrators change its database server machines,
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it is customary to register the change with grand.central.org for
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inclusion in this file. The file conforms to the required F<CellServDB>
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format, and so is a suitable basis for the F<CellServDB> file on a client
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machine. You can download this file from L<http://grand.central.org/>.
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=head1 EXAMPLES
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The following example shows entries for two cells in a client
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F<CellServDB> file and illustrates the required format.
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>abc.com # ABC Corporation
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192.12.105.2 #db1.abc.com
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192.12.105.3 #db2.abc.com
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[192.12.107.3] #db3.abc.com
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>test.abc.com abc.com # ABC Corporation Test Cell
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192.12.108.57 #testdb1.abc.com
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192.12.108.55 #testdb2.abc.com
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=head1 SEE ALSO
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L<afsd(8)>,
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L<bos_addhost(8)>,
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L<bos_listhosts(8)>,
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L<bos_removehost(8)>,
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L<bos_setcellname(8)>,
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L<buserver(8)>,
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L<fs_newcell(1)>,
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L<kaserver(8)>,
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L<klog(1)>,
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L<ptserver(8)>,
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L<vlserver(8)>,
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L<upclient(8)>,
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L<upserver(8)>
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I<OpenAFS Quick Start>
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=head1 COPYRIGHT
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IBM Corporation 2000. <http://www.ibm.com/> All Rights Reserved.
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This documentation is covered by the IBM Public License Version 1.0. It was
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converted from HTML to POD by software written by Chas Williams and Russ
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Allbery, based on work by Alf Wachsmann and Elizabeth Cassell.
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