Administration Reference

afsd

Purpose

Initializes the Cache Manager and starts related daemons.

Synopsis

afsd [-blocks <1024 byte blocks in cache>]  
     [-files <files in cache>]
     [-rootvol <name of AFS root volume>]
     [-stat <number of stat entries>]
     [-memcache]  [-cachedir <cache directory>]  
     [-mountdir <mount location>]
     [-daemons <number of daemons to use>]  
     [-nosettime]  [-verbose]  [-rmtsys]  [-debug]  
     [-chunksize <log(2) of chunk size>]
     [-dcache <number of dcache entries>]
     [-volumes <number of volume entries>]  
     [-biods <number of bkg I/O daemons (aix vm)>]
     [-prealloc <number of 'small' preallocated blocks>]
     [-confdir <configuration directory>]
     [-logfile <Place to keep the CM log>]  
     [-waitclose]  [-shutdown]  [-enable_peer_stats]  
     [-enable_process_stats]  [-help]

This command does not use the syntax conventions of the AFS command suites. Provide the command name and all option names in full.

Description

The afsd command initializes the Cache Manager on an AFS client machine by transferring AFS-related configuration information into kernel memory and starting several daemons. More specifically, the afsd command performs the following actions:

Sets a field in kernel memory that defines the machine's cell membership. Some Cache Manager-internal operations and system calls consult this field to learn which cell to execute in. (The AFS command interpreters refer to the /usr/vice/etc/ThisCell file instead.) This information is transferred into the kernel from the /usr/vice/etc/ThisCell file and cannot be changed until the afsd program runs again.
Places in kernel memory the names and Internet addresses of the database server machines in the local cell and (optionally) foreign cells. The appearance of a cell's database server machines in this list enables the Cache Manager to contact them and to access files in the cell. Omission of a cell from this list, or incorrect information about its database server machines, prevents the Cache Manager from accessing files in it.
The list of database server machines is transferred into the kernel from the /usr/vice/etc/CellServDB file. After initialization, use the fs newcell command to change the kernel-resident list without having to reboot.
Mounts the root of the AFS filespace on a directory on the machine's local disk, according to either the first field in the /usr/vice/etc/cacheinfo file (the default) or the afsd command's -mountdir argument. The conventional value is /afs.
Determines which volume to mount at the root of the AFS file tree. The default is the volume root.afs; use the -rootvol argument to override it. Although the base (read/write) form of the volume name is the appropriate value, the Cache Manager has a bias for accessing the read-only version of the volume (by convention, root.afs.readonly) if it is available.
Configures the cache on disk (the default) or in machine memory if the -memcache argument is provided. In the latter case, the afsd program allocates space in machine memory for caching, and the Cache Manager uses no disk space for caching even if the machine has a disk.
Defines the name of the local disk directory devoted to caching, when the -memcache argument is not used. If necessary, the afsd program creates the directory (its parent directory must already exist). It does not remove the directory that formerly served this function, if one exists.
The second field in the /usr/vice/etc/cacheinfo file is the source for this name, and the standard value is the /usr/vice/cache directory. Use the -cachedir argument to override the value in the cacheinfo file.
Sets the size of the cache. The default source for the value is the third field in the /usr/vice/etc/cacheinfo file, which specifies a number of kilobytes.
For a memory cache, the following arguments to the afsd command override the value in the cacheinfo file:
- The -blocks argument, to specify a different number of kilobyte blocks.
- The -dcache and -chunksize arguments together, to set both the number of dcache entries and the chunk size (see below for definition of these parameters). In this case, the afsd program derives cache size by multiplying the two values. Using this combination is not recommended, as it requires the issuer to perform the calculation beforehand to determine the resulting cache size.
- The -dcache argument by itself. In this case, the afsd program derives cache size by multiplying the value specified by the -dcache argument by the default memory cache chunk size of eight kilobytes. Using this argument is not recommended, as it requires the issuer to perform the calculation beforehand to determine the resulting cache size.
For satisfactory memory cache performance, the specified value must leave enough memory free to accommodate all other processes and commands that can run on the machine. If the value exceeds the amount of memory available, the afsd program exits without initializing the Cache Manager and produces the following message on the standard output stream:
```
   afsd: memCache allocation failure at number KB
   
```
where number is how many kilobytes were allocated just before the failure.
For a disk cache, use the -blocks argument to the afsd command to override the value in the cacheinfo file. The value specified in either way sets an absolute upper limit on cache size; values provided for other arguments (such as -dcache and -chunksize) never result in a larger cache. The afsd program rejects any setting larger than 95% of the partition size, and exits after generating an error message on the standard output stream, because the cache implementation itself requires a small amount of disk space and overfilling the partition can cause the client machine to panic.
To change the size of a disk cache after initialization without rebooting, use the fs setcachesize command; the setting persists until the afsd command runs again or the fs setcachesize command is reissued. The fs setcachesize command does not work for memory caches.
Sets the size of each cache chunk, and by implication the amount of data that the Cache Manager requests at a time from the File Server (how much data per fetch RPC, since AFS uses partial file transfer).
For a disk cache, a chunk is a Vn file and this parameter sets the maximum size to which each one can expand; the default is 64 KB. For a memory cache, each chunk is a collection of contiguous memory blocks; the default is size is 8 KB.
To override the default chunk size for either type of cache, use the -chunksize argument to provide an integer to be used as an exponent of two; see the Options section for details. For a memory cache, if total cache size divided by chunk size leaves a remainder, the afsd program rounds down the number of dcache entries, resulting in a slightly smaller cache.
Sets the number of chunks in the cache. For a memory cache, the number of chunks is equal to the cache size divided by the chunk size. For a disk cache, the number of chunks (Vn files) is set to the largest of the following unless the -files argument is used to set the value explicitly:
- 100
- 1.5 times the result of dividing cache size by chunk size (cachesize/chunksize * 1.5)
- The result of dividing cachesize by 10 KB (cachesize/10240)
Sets the number of dcache entries allocated in machine memory for storing information about the chunks in the cache.
For a disk cache, the /usr/vice/cache/CacheItems file contains one entry for each Vn file. By default, one half the number of these entries (but not more that 2,000) are duplicated as dcache entries in machine memory for quicker access.
For a memory cache, there is no CacheItems file so all information about cache chunks must be in memory as dcache entries. Thus, there is no default number of dcache entries for a memory cache; instead, the afsd program derives it by dividing the cache size by the chunk size.
To set the number of dcache entries, use the -dcache argument; the specified value can exceed the default limit of 2,000. Using this argument is not recommended for either type of cache. Increasing the number of dcache entries for a disk cache sometimes improves performance (because more entries are retrieved from memory rather than from disk), but only marginally. Using this argument for a memory cache requires the issuer to calculate the cache size by multiplying this value by the chunk size.
Sets the number of stat entries available in machine memory for caching status information about cached AFS files. The default is 300; use the -stat argument to override the default.
Randomly selects a file server machine in the local cell as the source for the correct time. Every five minutes thereafter, the local clock is adjusted (if necessary) to match the file server machine's clock.
Use the -nosettime flag to prevent the afsd command from selecting a time standard. This is recommended only on file server machines that are also acting as clients. File server machines maintain the correct time using the Network Time Protocol Daemon instead.

In addition to setting cache configuration parameters, the afsd program starts the following daemons. (On most system types, these daemons appear as nameless entries in the output of the UNIX ps command.)

One callback daemon, which handles callbacks. It also responds to the File Server's periodic probes, which check that the client machine is still alive.
One maintenance daemon, which performs the following tasks:
- Garbage collects obsolete data (for example, expired tokens) from kernel memory
- Synchronizes files
- Refreshes information from read-only volumes once per hour
- Does delayed writes for NFS clients if the machine is running the NFS/AFS Translator
One cache-truncation daemon, which flushes the cache when free space is required, by writing cached data and status information to the File Server.
One server connection daemon, which sends a probe to the File Server every few minutes to check that it is still accessible. It also synchronizes the machine's clock with the clock on a randomly-chosen file server machine, unless the -nosettime flag is used. There is always one server connection daemon.
One or more background daemons that improve performance by pre-fetching files and performing background (delayed) writes of saved data into AFS.
The default number of background daemons is two, enough to service at least five simultaneous users of the machine. To increase the number, use the -daemons argument. A value greater than six is not generally necessary.
On some system types, one Rx listener daemon, which listens for incoming RPCs.
On some system types, one Rx event daemon, which reviews the Rx system's queue of tasks and performs them as appropriate. Most items in the queue are retransmissions of failed packets.
On machines that run AIX with virtual memory (VM) integration, one or more VM daemons (sometimes called I/O daemons, which transfer data between disk and machine memory. The number of them depends on the setting of the -biods and -daemons arguments:
- If the -biods argument is used, it sets the number of VM daemons.
- If only the -daemons argument is used, the number of VM daemons is twice the number of background daemons.
- If neither argument is used, there are five VM daemons.

Cautions

Do not use the -shutdown parameter. It does not shutdown the Cache Manager effectively. Instead, halt Cache Manager activity by using the standard UNIX umount command to unmount the AFS root directory (by convention, /afs). The machine must then be rebooted to reinitialize the Cache Manager.

Options

-blocks

Specifies the number of kilobyte blocks to be made available for caching in the machine's cache directory (for a disk cache) or memory (for a memory cache), overriding the default defined in the third field of the /usr/vice/etc/cacheinfo file. For a disk cache, the value cannot exceed 95% of the space available in the cache partition. If using a memory cache, do not combine this argument with the -dcache argument, since doing so can possibly result in a chunk size that is not an exponent of 2.

-files

Specifies the number of Vn files to create in the cache directory for a disk cache, overriding the default that is calculated as described in the Description section. Each Vn file accommodates a chunk of data, and can grow to a maximum size of 64 KB by default. Do not combine this argument with the -memcache argument.

-rootvol

Names the read/write volume corresponding to the root directory for the AFS file tree (which is usually the /afs directory). This value overrides the default of the root.afs volume.

-stat

Specifies the number of entries to allocate in the machine's memory for recording status information about the AFS files in the cache. This value overrides the default of 300.

-memcache

Initializes a memory cache rather than a disk cache. Do not combine this flag with the -files argument.

-cachedir

Names the local disk directory to be used as the cache. This value overrides the default defined in the second field of the /usr/vice/etc/cacheinfo file.

-mountdir

Names the local disk directory on which to mount the root of the AFS filespace. This value overrides the default defined in the first field of the /usr/vice/etc/cacheinfo file. If a value other than the /afs directory is used, the machine cannot access the filespace of cells that do use that value.

-daemons

Specifies the number of background daemons to run on the machine. These daemons improve efficiency by doing prefetching and background writing of saved data. This value overrides the default of 2, which is adequate for a machine serving up to five users. Values greater than 6 are not generally more effective than 6.

Note: On AIX machines with integrated virtual memory (VM), the number of VM daemons is set to twice the value of this argument, if it is provided and the -biods argument is not. If both arguments are omitted, there are five VM daemons.

-nosettime

Prevents the Cache Manager from synchronizing its clock with the clock on a server machine selected at random, by checking the time on the server machine every five minutes. Use this flag only on a machine that is already using another time synchronization protocol (for example, a server machine that is running the runntp process).

-verbose

Generates a detailed trace of the afsd program's actions on the standard output stream.

-rmtsys

Initializes an additional daemon to execute AFS-specific system calls on behalf of NFS client machines. Use this flag only if the machine is an NFS/AFS translator machine serving users of NFS client machines who execute AFS commands.

-debug

Generates a highly detailed trace of the afsd program's actions on the standard output stream. The information is useful mostly for debugging purposes.

-chunksize

Sets the size of each cache chunk. The integer provided, which must be from the range 0 to 30, is used as an exponent on the number 2. It overrides the default of 16 for a disk cache (2¹⁶ is 64 KB) and 13 for a memory cache (2¹³ is 8 KB). A value of 0 or less, or greater than 30, sets chunk size to the appropriate default. Values less than 10 (which sets chunk size to a 1 KB) are not recommended. Combining this argument with the -dcache argument is not recommended because it requires that the issuer calculate the cache size that results.

-dcache

Sets the number of dcache entries in memory, which are used to store information about cache chunks. For a disk cache, this overrides the default, which is 50% of the number of Vn files (cache chunks). For a memory cache, this argument effectively sets the number of cache chunks, but its use is not recommended, because it requires the issuer to calculate the resulting total cache size (derived by multiplying this value by the chunk size). Do not combine this argument with the -blocks argument, since doing so can possibly result in a chunk size that is not an exponent of 2.

-volumes

Specifies the number of memory structures to allocate for storing volume location information. The default value is 50.

-biods

Sets the number of VM daemons dedicated to performing I/O operations on a machine running a version of AIX with virtual memory (VM) integration. If both this argument and the -daemons argument are omitted, the default is five. If this argument is omitted but the -daemons argument is provided, the number of VM daemons is set to twice the value of the -daemons argument.

Note:

Provide this argument only on a machine that runs AIX with VM integration.

-prealloc

Specifies the number of pieces of memory to preallocate for the Cache Manager's internal use. The default initial value is 400, but the Cache Manager dynamically allocates more memory as it needs it.

-confdir

Names a directory other than the /usr/vice/etc directory from which to fetch the cacheinfo, ThisCell, and CellServDB configuration files.

-logfile

Is obsolete and has no real effect. It specifies an alternate file in which to record a type of trace that the Cache Manager no longer generates; the default value is /usr/vice/etc/AFSLog.

-waitclose

Has no effect on the operation of the Cache Manager. The behavior it affected in previous versions of the Cache Manager, to perform synchronous writes to the File Server, is now the default behavior. To perform asynchronous writes in certain cases, use the fs storebehind command.

-shutdown

Shuts down the Cache Manager, but not in the most effective possible way. Do not use this flag.

-enable_peer_stats

Activates the collection of Rx statistics and allocates memory for their storage. For each connection with a specific UDP port on another machine, a separate record is kept for each type of RPC (FetchFile, GetStatus, and so on) sent or received. To display or otherwise access the records, use the Rx Monitoring API.

-enable_process_stats

Activates the collection of Rx statistics and allocates memory for their storage. A separate record is kept for each type of RPC (FetchFile, GetStatus, and so on) sent or received, aggregated over all connections to other machines. To display or otherwise access the records, use the Rx Monitoring API.

-help

Prints the online help for this command. All other valid options are ignored.

Examples

The afsd command is normally included in the machine's AFS initialization file, rather than typed at the command shell prompt. For most disk caches, the appropriate form is

   /usr/vice/etc/afsd

The following command is appropriate when enabling a machine to act as an NFS/AFS Translator machine serving more than five users.

   /usr/vice/etc/afsd -daemons 4 -rmtsys

The following command initializes a memory cache and sets chunk size to 16 KB (2¹⁴).

   /usr/vice/etc/afsd -memcache -chunksize 14

Privilege Required

The issuer must be logged in as the local superuser root.

Related Information

CacheItems

CellServDB (client version)

ThisCell (client version)

cacheinfo