afsd, afsd.fuse - Initializes the Cache Manager and starts related daemons
afsd [-afsdb [<true/false>]] [-backuptree [<true/false>]] [-biods <number of bkg I/O daemons (aix vm)>] [-blocks <1024 byte blocks in cache>] [-cachedir <cache directory>] [-chunksize <log(2) of chunk size>] [-config <configuration file>] [-daemons <number of daemons to use>] [-dcache <number of dcache entries>] [-debug] [-dynroot [<true/false/all>]] [-enable_peer_stats] [-enable_process_stats] [-fakestat [<true/false/all>]] [-files <files in cache>] [-files_per_subdir <log(2) of files per dir> ] [-help] [-keytab <path to keytab for system tokens>] [-principal <keytab principal for system tokens>] [-logfile <Place to keep the CM log>] [-mem_alloc_sleep] [-memcache] [-mountdir <mount location>] [-mountopts <mount options>] [-exportnfs] [-nomount] [-postscript <path to script>] [-rmtsys] [-rootvol <name of AFS root volume>] [-rxbind] [-rxmaxmtu value for maximum MTU ] -rxwindow <maximum window size in packets>] [-rxpck value for rx_extraPackets ] [-shutdown] [-splitcache <RW/RO ratio>] [-stat <number of stat entries>] [-verbose] [-dynamic-vcaches [<true/false>]] [-volumes <number of volume entries>] [-rxmaxfrags <max # of fragments>] [-discovery]
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:
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. This information is transferred into the kernel 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.
By default, 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. Alternatively, when the -afsdb false option is used, the list of database server machines is transferred into the kernel from the /etc/yfs/yfs-client.conf file.
Mounts the root of the AFS filespace on a directory on the machine's local disk, according to 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 standard value is /var/cache/yfs.
Sets the size of the cache, as a number of kilobytes.
For a memory cache, the following arguments to the afsd command control the cache size:
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 The value specified 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. 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.
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:
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 /var/cache/yfs/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 based on the size of the cache. Use the -stat argument to override the default.
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.
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. 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.
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 state changes, the server notifies the client and all cached state information is discarded. In order to enable full functionality on the AFS client, including all command-line utilities, the following UDP ports must be open on all firewalls between the client and the server:
fileserver 7000/udp cachemanager 7001/udp (default, but can be any unused port) ptserver 7002/udp vlserver 7003/udp volserver 7005/udp bosserver 7007/udp
However, the cache manager only contacts the fileserver and vlserver.
Clients must be able to contact your Kerberos KDC to authenticate. The standard Kerberos ports are:
kerberos 88/udp and 88/tcp kerberos-adm 749/tcp
Be sure to set the UDP timeouts on the firewall to be at least 12 minutes for the best callback performance.
afsd.fuse is only available if OpenAFS was built with the
--enable-fuse-client configure switch. It should be considered experimental.
Enable or disable afsdb support. When this feature is enabled (default), DNS will be used to lookup the SRV or AFSDB records for the database servers for each cell instead of using the values in the yfs-client.conf 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 yfs-client.conf. The format of SRV records is defined in RFC 5864, and the AFSDB record format is in RFC 1183.
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. This is enabled by default.
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.
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). 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.
Names the local disk directory to be used as the cache.
Sets the size of each cache chunk. The integer provided, which must be from the range
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
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.
The location of the configuration file to be used. The default name is yfs-client.conf and the default location is /etc/yfs.
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
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.
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.
Generates a highly detailed trace of the afsd program's actions on the standard output stream. The information is useful mostly for debugging purposes.
The behaviour of the AFS client when the -dynroot option is set to false 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 the local cell and other cells as configured by the AFS cell administrator.
With the default -dynroot true setting, the AFS client does not mount the root.afs volume on /afs. Instead it uses the local cell and other cells explicitly marked to be shown to populate the listing of cells in /afs. Cells other than these cells are not shown by default until a lookup occurs. Cell aliases are shown as normal, although they may appear to be dangling links until traversed.
/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 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.
When -dynroot all is specified, all cells listed in the local configuration are shown.
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. cellname.domain.com is aliased to cellname). However, with dynroot, the local system administrator can limit the default contents of /afs by installing a stripped-down yfs-client.conf 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.
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.
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.
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 option is useful on Mac OS X so that the Finder program doesn't try to contact every AFS cell the system knows about. This option is enabled (true) by default.
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.
Choosing -fakestat all returns fake values for stat calls on all mounts, not just cross-cell mounts.
The -fakestat setting will be forced to false if -exportnfs is on, as it can interfere with the nfs server's path reconnection logic and result in stale file handle errors on the nfs clients.
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.
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).
Prints the online help for this command. All other valid options are ignored.
Provides the path to a keytab file which should contain the key for a Kerberos principal which the Cache Manager will maintain authentication for at all times. If -principal is not specified, then the first entry in the keytab file is used.
Specifies the Kerberos v5 principal name to use when selecting a keytab entry from the keytab file. If -principal is not specified, then the principal associated with the first entry in the keytab file is used as the system token authentication identity.
Initializes a memory cache rather than a disk cache. Do not combine this flag with the -files argument.
Names the local disk directory on which to mount the root of the AFS filespace. If a value other than the /afs directory is used, the machine cannot access the filespace of cells that do use that value.
Allows specifying mount options as would be specified with mount -o. Typically this will not be used, but for Linux, SELinux context may be specified with a mountopts of
context=SELinux context string
On Linux, if this field is not set, we default to
Enable exporting paths under /afs over nfs. Note that this flag also disables -fakestat.
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.
Provides the path to a script which will be run after Cache Manager initialization is complete.
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.
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 unless -dynroot false is given.
Bind the Rx socket (one interface only).
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.
Specify the maximum transmission unit (MTU) value. The value must be between the minimum (520) and maximum (16384) Rx packet sizes.
It artificially limits the maximum Rx data packet size that will be transmitted. It can be used when the maximum size that can be successfully transmitted is smaller than the reported network interface MTU.
Specify the maximum sliding window size that RX may use on the wire. Larger windows improve performance on networks with a high latency, at the expense of higher memory usage. The value specified must be less than the maximum RX window size of 65535.
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 127.0.0.1 -port 7001 -rxstats" command shows no free Rx packets. Increasing this value may improve OpenAFS client performance in some circumstances.
Shuts down the Cache Manager. Before calling afsd with this option, unmount the AFS file system with umount.
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.
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.
Generates a detailed trace of the afsd program's actions on the standard output stream.
Specifies the number of memory structures to allocate for storing volume location information. The default value is
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. If set to false, this option will disable this new functionality and honor the '-stat' setting.
Use mDNS/DNS-SD Zeroconf to add cells announced on the local network and associated servers to the kernel's internal table of cells.
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
The following command is appropriate when enabling a machine to act as an NFS/AFS Translator machine serving more than five users.
% /usr/sbin/afsd -daemons 4 -rmtsys
The following command initializes a memory cache and sets chunk size to 16 KB (2^14).
% /usr/sbin/afsd -memcache -chunksize 14
The following command sets an SELinux context on a mountpoint.
% /usr/sbin/afsd -mountopts "context=unconfined_u:object_r:user_home_t:s0"
The issuer must be logged in as the local superuser root.
fs_newcell(1), afs_cache(5), yfs-client.conf(5), auristorfs_linux_exportnfs(7)
RFC 5864 http://www.ietf.org/rfc/rfc5864.txt RFC 1183 http://www.ietf.org/rfc/rfc1183.txt
IBM Corporation 2000. <http://www.ibm.com/> All Rights Reserved.
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