=head1 NAME

CellServDB - Lists the database server machines in AFS cells

=head1 DESCRIPTION

There are two versions of the F<CellServDB> file, both of which have the
same format.  One version is used by an AFS client and lists all of the
database server machines in the local cell and any foreign cell that is to
be accessible from the local client machine.  The other version is used on
servers and lists only the database servers in the local cell.

=head2 Client CellServDB

The client version of the CellServDB file lists the database server
machines in the local cell and any foreign cell that is to be accessible
from the local client machine. Database server machines run the
Authentication Server, Backup Server, Protection Server, and Volume
Location (VL) Server (the B<kaserver>, B<buserver>, B<ptserver>, and
B<vlserver>) processes, which maintain the cell's administrative AFS
databases.

The Cache Manager and other processes running on a client machine use the
list of a cell's database server machines when performing several common
functions, including:

=over 4

=item *

Fetching files. The Cache Manager contacts the VL Server to learn
the location of the volume containing a requested file or directory.

=item *

Authenticating users. Client-side authentication programs (such as an
AFS-modified login utility or the B<klog> command interpreter) contact the
Authentication Server to obtain a server ticket, which the AFS server
processes accept as proof that the user is authenticated.

=item *

Creating protection groups. The B<pts> command interpreter contacts the
Protection Server when users create protection groups or request
information from the Protection Database.

=back

The Cache Manager reads the CellServDB file into kernel memory as it
initializes, and not again until the machine next reboots. To enable users
on the local machine to continue accessing the cell correctly, update the
file whenever a database server machine is added to or removed from a
cell. To update the kernel-resident list of database server machines
without rebooting, use the B<fs newcell> command.

The F<CellServDB> file is in ASCII format and must reside in the
F</usr/vice/etc> directory on each AFS client machine. Use a text editor
to create and maintain it.

The client version of the F<CellServDB> file is distinct from the server
version, which resides in the F</usr/afs/etc> directory on each AFS server
machine. The client version lists the database server machines in every
AFS cell that the cell administrator wants the machine's users to be able
to access, whereas the server version lists only the local cell's database
server machines.

=head2 Server CellServDB

The server version of the F<CellServDB> file lists the local cell's
database server machines. These machines run the Authentication Server,
Backup Server, Protection Server, and Volume Location (VL) Server (the
B<kaserver>, B<buserver>, B<ptserver>, and B<vlserver>) processes, which
maintain the cell's administrative AFS databases. The initial version of
the file is created with the B<bos setcellname> command during the
installation of the cell's server machine, which is automatically recorded
as the cell's first database server machine. When adding or removing
database server machines, be sure to update this file appropriately. It
must reside in the F</usr/afs/etc> directory on each AFS server machine.

The database server processes consult the F<CellServDB> file to learn
about their peers, with which they must maintain constant connections in
order to coordinate replication of changes across the multiple copies of
each database. The other AFS server processes consult the file to learn
which machines to contact for information from the databases when they
need it.

Although the server F<CellServDB> file is in ASCII format, do not use a
text editor to alter it. Instead always use the appropriate commands from
the B<bos> command suite:

=over 4

=item *

The B<bos addhost> command to add a machine to the file.

=item *

The B<bos listhosts> command to display the list of machines from the
file.

=item *

The B<bos removehost> command to remove a machine from the file.

=back

In cells that use the Update Server to distribute the contents of the
F</usr/afs/etc> directory, it is customary to edit only the copy of the
file stored on the system control machine. Otherwise, edit the file on
each server machine individually. For instructions on adding and removing
database server machine, see the I<IBM AFS Quick Beginnings> chapter on
installing additional server machines.

=head2 CellServDB Format

Both F<CellServDB> files have the same format:

=over 4

=item *

The first line begins at the left margin with the greater-than character
(C<< > >>), followed immediately by the cell's name without an intervening
space. Optionally, a comment can follow any number of spaces and a number
sign (C<#>), perhaps to identify the organization associated with the
cell.

=item *

Each subsequent line in the entry identifies one of the cell's database
server machines, with the indicated information in order:

=over 4

=item *

The database server machine's IP address in dotted-decimal format.

=item *

One or more spaces.

=item *

A number sign (#), followed by the machine's fully qualified hostname
without an intervening space. This number sign does not indicate that the
hostname is a comment. It is a required field.

=back

=back

No extra blank lines or newline characters are allowed in the file, even
after the last entry. Their presence can prevent the Cache Manager from
reading the file into kernel memory, resulting in an error message.

grand.central.org maintains a list of the database server machines in all
cells that have registered themselves as receptive to access from foreign
cells. When a cell's administrators change its database server machines,
it is customary to register the change with grand.central.org for
inclusion in this file. The file conforms to the required F<CellServDB>
format, and so is a suitable basis for the F<CellServDB> file on a client
machine.  You can download this file from L<http://grand.central.org/>.

=head1 EXAMPLES

The following example shows entries for two cells in a client
F<CellServDB> file and illustrates the required format.

   >abc.com        # ABC Corporation
   192.12.105.2	        #db1.abc.com
   192.12.105.3	        #db2.abc.com
   192.12.107.3	        #db3.abc.com
   >test.abc.com   # ABC Corporation Test Cell
   192.12.108.57        #testdb1.abc.com
   192.12.108.55        #testdb2.abc.com

=head1 SEE ALSO

L<bos_addhost(8)>,
L<bos_listhosts(8)>,
L<bos_removehost(8)>,
L<bos_setcellname(8)>,
L<buserver(8)>,
L<fs_newcell(1)>,
L<kaserver(8)>,
L<klog(1)>,
L<ptserver(8)>,
L<vlserver(8)>,
L<upclient(8)>,
L<upserver(8)>

I<IBM AFS Quick Beginnings>

=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.
