=head1 NAME

afsd - Initializes the Cache Manager and starts related daemons

=head1 SYNOPSIS

=for html
<div class="synopsis">

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

=for html
</div>

=head1 DESCRIPTION

The B<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 B<afsd> command
performs the following actions:

=over 4

=item *

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 F</usr/vice/etc/ThisCell> file instead.) This
information is transferred into the kernel from the
F</usr/vice/etc/ThisCell> file and cannot be changed until the B<afsd>
program runs again.

=item *

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 F</usr/vice/etc/CellServDB> file. After initialization, use the B<fs
newcell> command to change the kernel-resident list without having to
reboot.

=item *

Mounts the root of the AFS filespace on a directory on the machine's local
disk, according to either the first field in the
F</usr/vice/etc/cacheinfo> file (the default) or the B<afsd> command's
B<-mountdir> argument. The conventional value is F</afs>.

=item *

Determines which volume to mount at the root of the AFS file tree.  The
default is the volume C<root.afs>; use the B<-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, C<root.afs.readonly>) if
it is available.

=item *

Configures the cache on disk (the default) or in machine memory if the
B<-memcache> argument is provided. In the latter case, the B<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.

=item *

Defines the name of the local disk directory devoted to caching, when the
B<-memcache> argument is not used. If necessary, the B<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 F</usr/vice/etc/cacheinfo> file is the source for
this name, and the standard value is the F</usr/vice/cache> directory. Use
the B<-cachedir> argument to override the value in the B<cacheinfo> file.

=item *

Sets the size of the cache. The default source for the value is the third
field in the F</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 B<cacheinfo> file:

=over 4

=item *

The B<-blocks> argument, to specify a different number of kilobyte blocks.

=item *

The B<-dcache> and B<-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 B<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.

=item *

The B<-dcache> argument by itself. In this case, the B<afsd> program
derives cache size by multiplying the value specified by the B<-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.

=back

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 B<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 B<-blocks> argument to the B<afsd> command to
override the value in the B<cacheinfo> file. The value specified in either
way sets an absolute upper limit on cache size; values provided for other
arguments (such as B<-dcache> and B<-chunksize>) never result in a larger
cache. The B<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 B<fs setcachesize> command; the setting persists until the B<afsd>
command runs again or the B<fs setcachesize> command is reissued. The B<fs
setcachesize> command does not work for memory caches.

=item *

Sets the size of each cache I<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 F<VI<n>> 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
B<-chunksize> argument to provide an integer to be used as an exponent of
two; see L<OPTIONS> for details. For a memory cache, if total cache size
divided by chunk size leaves a remainder, the B<afsd> program rounds down
the number of dcache entries, resulting in a slightly smaller cache.

=item *

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 (F<VI<n>> files) is set to the largest
of the following unless the B<-files> argument is used to set the value
explicitly:

=over 4

=item *

100

=item *

1.5 times the result of dividing cache size by chunk size
(I<cachesize>/I<chunksize> * 1.5)

=item *

The result of dividing cachesize by 10 KB (I<cachesize>/10240)

=back

=item *

Sets the number of I<dcache entries> allocated in machine memory for
storing information about the chunks in the cache.

For a disk cache, the F</usr/vice/cache/CacheItems> file contains one
entry for each F<VI<n>> 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 F<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 B<afsd>
program derives it by dividing the cache size by the chunk size.

To set the number of dcache entries, use the B<-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.

=item *

Sets the number of I<stat> entries available in machine memory for caching
status information about cached AFS files. The default is 300; use the
B<-stat> argument to override the default.

=item *

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 B<-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.

=back

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

=over 4

=item *

One I<callback> daemon, which handles callbacks. It also responds to the
File Server's periodic probes, which check that the client machine is
still alive.

=item *

One I<maintenance> daemon, which performs the following tasks:

=over 4

=item *

Garbage collects obsolete data (for example, expired tokens) from kernel
memory.

=item *

Synchronizes files.

=item *

Refreshes information from read-only volumes once per hour.

=item *

Does delayed writes for NFS clients if the machine is running the NFS/AFS
Translator.

=back

=item *

One I<cache-truncation> daemon, which flushes the cache when free space is
required, by writing cached data and status information to the File
Server.

=item *

One I<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 B<-nosettime> flag is used. There is always one
server connection daemon.

=item *

One or more I<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 B<-daemons> argument. A value greater than six is not generally
necessary.

=item *

On some system types, one I<Rx listener> daemon, which listens for
incoming RPCs.

=item *

On some system types, one I<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.

=item *

On machines that run AIX with virtual memory (VM) integration, one or more
I<VM> daemons (sometimes called I<I/O> daemons, which transfer data
between disk and machine memory. The number of them depends on the setting
of the B<-biods> and B<-daemons> arguments:

=over 4

=item *

If the B<-biods> argument is used, it sets the number of VM daemons.

=item *

If only the B<-daemons> argument is used, the number of VM daemons is
twice the number of background daemons.

=item *

If neither argument is used, there are five VM daemons.

=back

=back

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

=head1 CAUTIONS

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

=head1 OPTIONS

=over 4

=item B<-blocks> <I<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
F</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 B<-dcache> argument, since
doing so can possibly result in a chunk size that is not an exponent of 2.

=item B<-files> <I<files in cache>>

Specifies the number of F<VI<n>> files to create in the cache
directory for a disk cache, overriding the default that is calculated as
described in L<DESCRIPTION>. Each F<VI<n>> 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 B<-memcache> argument.

=item B<-rootvol> <I<name of AFS root volume>>

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

=item B<-stat> <I<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. This value
overrides the default of C<300>.

=item B<-memcache>

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

=item B<-cachedir> <I<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
F</usr/vice/etc/cacheinfo> file.

=item B<-mountdir> <I<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 F</usr/vice/etc/cacheinfo> file. If a value other than the F</afs>
directory is used, the machine cannot access the filespace of cells that
do use that value.

=item B<-daemons> <I<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 C<2>, which is adequate
for a machine serving up to five users. Values greater than C<6> are not
generally more effective than C<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 B<-biods> argument is not. If both arguments are omitted, there
are five VM daemons.

=item B<-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 B<runntp> process).

=item B<-verbose>

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

=item B<-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.

=item B<-debug>

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

=item B<-chunksize> <I<chunk size>>

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

=item B<-dcache> <I<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 F<VI<n>> 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
B<-blocks> argument, since doing so can possibly result in a chunk size
that is not an exponent of 2.

=item B<-volumes> <I<number of volume entries>>

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

=item B<-biods> <I<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 B<-daemons> argument are omitted, the default
is five. If this argument is omitted but the B<-daemons> argument is
provided, the number of VM daemons is set to twice the value of the
B<-daemons> argument.

=item B<-prealloc> <I<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 C<400>, but the Cache
Manager dynamically allocates more memory as it needs it.

=item B<-confdir> <I<configuration directory>>

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

=item B<-logfile> <I<log file location>>

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 F</usr/vice/etc/AFSLog>.

=item B<-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 B<fs storebehind> command.

=item B<-shutdown>

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

=item B<-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.

=item B<-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.

=item B<-help>

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

=back

=head1 EXAMPLES

The B<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 (2^14).

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

=head1 PRIVILEGE REQUIRED

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

=head1 SEE ALSO

L<afs_cache(5)>,
L<CellServDB(5)>,
L<cacheinfo(5)>

=head1 COPYRIGHT

IBM Corporation 2000. <http://www.ibm.com/> 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.
