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Manual Reference Pages  -  AFSD (8)

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afsd, afsd.fuse - Initializes the Cache Manager and starts related daemons



afsd [-afsdb] [-backuptree]
[-biods <number of bkg I/O daemons (aix vm)>]
[-blocks <1024 byte blocks in cache>]
[-cachedir <cache directory>]
[-chunksize <log(2) of chunk size>]
[-confdir <configuration directory>]
[-daemons <number of daemons to use>]
[-dcache <number of dcache entries>] [-debug]
[-dynroot] [-dynroot-sparse] [-enable_peer_stats]
[-enable_process_stats] [-fakestat] [-fakestat-all]
[-files <files in cache>]
[-files_per_subdir <log(2) of files per dir> ]
[-help] [-logfile <Place to keep the CM log>]
[-mem_alloc_sleep] [-memcache]
[-mountdir <mount location>] [-nomount]
[-prealloc <number of ’small’ preallocated blocks>]
[-rmtsys] [-rootvol <name of AFS root volume>]
[-rxbind] [-rxmaxmtu value for maximum MTU ]
[-rxpck value for rx_extraPackets ]
[-settime] [-shutdown]
[-splitcache <RW/RO ratio>]
[-stat <number of stat entries>] [-verbose]
[-volumes <number of volume entries>]
[-waitclose] [-rxmaxfrags <max # of fragments>]


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. afsd.fuse is an experimental variant that initializes a FUSE-based Cache Manager instead of one based on a kernel module.

The afsd command performs the following actions:
o 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/local/etc/openafs/ThisCell file instead.) This information is transferred into the kernel from the /usr/local/etc/openafs/ThisCell file and cannot be changed until the afsd program runs again.
o 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.

By default, the list of database server machines is transferred into the kernel from the /usr/local/etc/openafs/CellServDB file. Alternatively, when the -afsdb option is used, the list of database server machines is taken from the DNS SRV or AFSDB records for each cell. After initialization, use the fs newcell command to change the kernel-resident list without having to reboot.

o 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/local/etc/openafs/cacheinfo file (the default) or the afsd command’s -mountdir argument. The conventional value is /afs.
o 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.
o 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.
o 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/local/etc/openafs/cacheinfo file is the source for this name. The standard value is /usr/vice/cache. Use the -cachedir argument to override the value in the cacheinfo file.

o Sets the size of the cache. The default source for the value is the third field in the /usr/local/etc/openafs/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:
o The -blocks argument, to specify a different number of kilobyte blocks.
o 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.
o 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.

o 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. For a memory cache, each chunk is a collection of contiguous memory blocks. The default for a disk cache is between 256 KB and 1 MB depending on the size of the cache. The default for a memory cache 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 OPTIONS 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.

o 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:
o 100
o 1.5 times the result of dividing cache size by chunk size (cachesize/chunksize * 1.5)
o The result of dividing cachesize by 10 KB (cachesize/10240)
o 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.

o Sets the number of stat entries available in machine memory for caching status information about cached AFS files. The default is based on the size of the cache. Use the -stat argument to override the default.
o If the -settime option is specified, then it 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. This is not enabled by default. It is recommended, instead, that the Network Time Protocol Daemon be used to synchronize the time.
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.)
o 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.
o One maintenance daemon, which performs the following tasks:
o Garbage collects obsolete data (for example, expired tokens) from kernel memory.
o Synchronizes files.
o Refreshes information from read-only volumes once per hour.
o Does delayed writes for NFS clients if the machine is running the NFS/AFS Translator.
o One cache-truncation daemon, which flushes the cache when free space is required, by writing cached data and status information to the File Server.
o One server connection daemon, which sends a probe to the File Server every few minutes to check that it is still accessible. If the -settime option is set, it also synchronizes the machine’s clock with the clock on a randomly-chosen file server machine. There is always one server connection daemon.
o 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.

o On some system types, one Rx listener daemon, which listens for incoming RPCs.
o 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.
o 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:
o If the -biods argument is used, it sets the number of VM daemons.
o If only the -daemons argument is used, the number of VM daemons is twice the number of background daemons.
o If neither argument is used, there are five VM daemons.
afsd.fuse is a variant of afsd that, instead of initializing a Cache Manager implemented as a kernel module, initializes a FUSE-based AFS client. FUSE (Filesystem in USErspace) is a Linux-only mechanism for providing a file system through a purely user-space daemon without a kernel module component. afsd.fuse takes all of the same options as afsd.

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


Before using the -shutdown parameter, use the standard UNIX umount command to unmount the AFS root directory (by convention, /afs). On Linux, unloading the AFS kernel module and then loading it again before restarting AFS after -shutdown is recommended.

AFS has for years had difficulties with being stopped and restarted without an intervening reboot. While most of these issues have been ironed out, stopping and restarting AFS is not recommended unless necessary and rebooting before restarting AFS is still the safest course of action. This does not apply to Linux; it should be safe to restart the AFS client on Linux without rebooting.

In contrast to many client-server applications, not all communication is initiated by the client. When the AFS client opens a file, it registers a callback with the AFS server. If the file changes, the server notifies the client that the file has changed and that all cached copies should be discarded. In order to enable full functionality on the AFS client, including all command-line utilities, the following UDP ports must be open on an firewalls between the client and the server:

   fileserver      7000/udp
   cachemanager    7001/udp (OpenAFS client. Arla uses 4711/udp)
   ptserver        7002/udp
   vlserver        7003/udp
   kaserver        7004/udp (not needed with Kerberos v5)
   volserver       7005/udp
   reserved        7006/udp (for future use)
   bosserver       7007/udp

Clients will also need to be able to contact your Kerberos KDC to authenticate. If you are using kaserver and klog, you need to allow inbound and outbound UDP on ports >1024 (probably 1024<port<2048 would suffice depending on the number of simultaneous klogs).

Be sure to set the UDP timeouts on the firewall to be at least twenty minutes for the best callback performance.

afsd.fuse was first introduced in OpenAFS 1.5.74. It is only available if OpenAFS was built with the --enable-fuse-client configure switch. It should be considered experimental.


-afsdb Enable afsdb support. This will use DNS to lookup the SRV or AFSDB records and use that for the database servers for each cell instead of the values in the CellServDB file. This has the advantage of only needing to update one set of DNS records to reconfigure the AFS clients for a new database server as opposed to touching all of the clients, and also allows one to access a cell without preconfiguring its database servers in CellServDB. The format of SRV records is defined in RFC 5864, and the AFSDB record format is in RFC 1183.
-backuptree Prefer backup volumes for mountpoints in backup volumes. This option means that the AFS client will prefer to resolve mount points to backup volumes when a parent of the current volume is a backup volume. This is similar to the standard behaviour of preferring read-only volumes over read-write volumes when the parent volume is a read-only volume.
-biods <number of I/O daemons> 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.
-blocks <blocks in cache> 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/local/etc/openafs/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.
-cachedir <cache directory> Names the local disk directory to be used as the cache. This value overrides the default defined in the second field of the /usr/local/etc/openafs/cacheinfo file.
-chunksize <chunk size> 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. If not supplied, a default chunksize will be determined based on the cache type and cache size, and will range from 13 (8KB) for memory cache and 18 to 20 (256 KB to 1MB) for disk cache. 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.

-chunksize is an important option when tuning for performance. Setting this option to larger values can increase performance when dealing with large files.

-confdir <configuration directory> Names a directory other than the /usr/local/etc/openafs directory from which to fetch the cacheinfo, ThisCell, and CellServDB configuration files.
-daemons <number of daemons to use> 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.

-dcache <number of dcache entries> 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.
-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.
-dynroot The standard behaviour of the AFS client without the -dynroot option is to mount the root.afs volume from the default cell on the /afs path. The /afs folder and root.afs volume traditionally shows the folders for ThisCell and other cells as configured by the AFS cell administrator.

The -dynroot option changes this. Using this option, the AFS client does not mount the root.afs volume on /afs. Instead it uses the contents of the CellServDB file to populate the listing of cells in /afs. This is known as a DYNamic ROOT. A cell is not contacted until the path /afs/cellname if accessed. This functions similarly to an automounter. The main advantage of using -dynroot is that the AFS client will start properly even without network access, whereas the client not using -dynroot will freeze upon startup if cannot contact the default cell specified in ThisCell and mount the root.afs volume. Dynamic root mode is also sometimes called travelling mode because it works well for laptops which don’t always have network connectivity.

Two advantages of not using dynroot are that listing /afs will usually be faster because the contents of /afs are limited to what the AFS administrator decides and that symbolic links are traditionally created by the AFS administrator to provide a short name for the cell (i.e. is aliased to cellname). However, with dynroot, the local system administrator can limit the default contents of /afs by installing a stripped-down CellServDB file, and if dynroot is in effect, the CellAlias file can be used to provide shortname for common AFS cells which provides equivalent functionality to the most commonly used symbolic links.

When the dynamic root (-dynroot, -dynroot-sparse) and the fake stat (-fakestat, -fakestat-all) modes are in effect, the cache manager provides a special directory named /afs/.:mount which allows access to volumes by volume name or ID. The /afs/.:mount directory appears to be empty, but any name in the form of cell:volume will be resolved as a read-write mount point to the specified volume. This dynamic mount feature is recommended only for temporary access to a volume. Linux-based cache managers provide this dynamic mount feature even when dynamic root (-dynroot, -dynroot-sparse) is not in effect.

-dynroot-sparse In addition to operating in the manner described for dynroot above, cells other than the local cell are not shown by default until a lookup occurs. Cell aliases as set in the CellAliases file are shown as normal, although they may appear to be dangling links until traversed.
-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.
-fakestat Return fake values for stat calls on cross-cell mounts. This option makes an ls -l of /afs much faster since each cell isn’t contacted, and this and the -fakestat-all options are useful on Mac OS X so that the Finder program doesn’t try to contact every AFS cell the system knows about.

Note that, for the purposes of -fakestat, local cellular mounts count as cross-cell mounts. That is, if the local cell is localcell, a mount for localcell:root.cell will count as a cross-cell mount and so stat calls for it will be faked with -fakestat. In practice, local cellular mounts are rare and generally discouraged, so this should not generally make a difference.

-fakestat-all Return fake values for stat calls on all mounts, not just cross-cell mounts. This and the -fakestat options are useful on Mac OS X so that the Finder program doesn’t hang when browsing AFS directories.
-files <files in cache> 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 DESCRIPTION. 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.
-files_per_subdir <files per cache subdirectory> Limits the number of cache files in each subdirectory of the cache directory. The value of the option should be the base-two log of the number of cache files per cache subdirectory (so 10 for 1024 files, 14 for 16384 files, and so forth).
-help Prints the online help for this command. All other valid options are ignored.
-logfile <log file location> This option is obsolete and no longer has any effect.
-mem_alloc_sleep This option is obsolete and no longer has any effect.
-memcache Initializes a memory cache rather than a disk cache. Do not combine this flag with the -files argument.
-mountdir <mount location> 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/local/etc/openafs/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.
-nomount Do not mount AFS on startup. The afs global mount must be mounted via some other means. This is useful on Mac OS X where /afs is sometimes mounted in /Network/afs like other network file systems.
-nosettime This is enabled by default. It 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. This is the recommended behavior; instead of the AFS Cache Manager, the Network Time Protocol Daemon should be used to synchronize the system time.
-prealloc <number of preallocated blocks> 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.
-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.
-rootvol <name of AFS root volume> 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. This option is ignored if -dynroot is given.
-rxbind Bind the Rx socket (one interface only).
-rxmaxfrags <max # of fragments> Set a limit for the maximum number of UDP fragments Rx will send per Rx packet, and the maximum number of fragments Rx thinks it can receive when advertising its receive size to peers. Practically speaking, setting this option means that you will not see Rx data packets that are broken into more than N fragments, where N is the value specified for this option. Setting this option to 1 effectively prevents fragmentation, and can be useful when dealing with networking equipment that does not properly handle UDP fragments.

Note that this option just specifies a maximum. The actual number of fragments seen on the wire may be less than what is specified, depending on the configuration of the peer.

-rxmaxmtu <value for maximum MTU> Set a limit for the largest maximum transfer unit (network packet size) that the AFS client on this machine will be willing to transmit. This switch can be used where an artificial limit on the network precludes packets as large as the discoverable MTU from being transmitted successfully.
-rxpck <value for rx_extraPackets> Set rx_extraPackets to this value. This sets the number of extra Rx packet structures that are available to handle Rx connections. This value should be increased if the rxdebug -port 7001 -rxstats command shows no free Rx packets. Increasing this value may improve OpenAFS client performance in some circumstances.
-settime Enable native AFS time synchronization. This option is the opposite of -nosettime and cannot be used with the -nosettime option.
-shutdown Shuts down the Cache Manager. Before calling afsd with this option, unmount the AFS file system with umount.
-splitcache <RW/RO Ratio> This allows the user to set a certain percentage of the AFS cache be reserved for read/write content and the rest to be reserved for read-only content. The ratio should be written as a fraction. For example, -splitcache 75/25 devotes 75% of your cache space to read/write content and 25% to read-only.
-stat <number of stat entries> Specifies the number of entries to allocate in the machine’s memory for recording status information about the AFS files in the cache. If this value is not specified, the number of stat entires will be autotuned based on the size of the disk cache.
-verbose Generates a detailed trace of the afsd program’s actions on the standard output stream.
-volumes <number of volume entries> Specifies the number of memory structures to allocate for storing volume location information. The default value is 200.
-disable-dynamic-vcaches By default, dynamic vcache overrides the -stat option by using the value of -stat (or the default) as the initial size of the stat (or vcache) pool and increases the pool dynamically as needed on supported platforms. This flag will disable this new functionality and honor the ’-stat’ setting.
-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.


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/local/etc/openafs/afsd

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

   % /usr/local/etc/openafs/afsd -daemons 4 -rmtsys

The following command initializes a memory cache and sets chunk size to 16 KB (2^14).

   % /usr/local/etc/openafs/afsd -memcache -chunksize 14


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


fs_newcell(1), afs_cache(5), CellServDB(5), cacheinfo(5)

RFC 5864 <> RFC 1183 <>


IBM Corporation 2000. <> All Rights Reserved.

This documentation is covered by the IBM Public License Version 1.0. It was converted from HTML to POD by software written by Chas Williams and Russ Allbery, based on work by Alf Wachsmann and Elizabeth Cassell.

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