Provided by: openafs-client_1.8.12.1-1_amd64 
NAME
CellServDB - Lists the database server machines in AFS cells
DESCRIPTION
There are two versions of the 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 need
list only the database servers in the local cell; in some configurations it can be a link to the same
file the client uses.
Client CellServDB
Along with AFSDB and SRV entries in DNS, 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 (optional), Backup Server (optional),
Protection Server, and Volume Location (VL) Server (the kaserver, buserver, ptserver, and 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:
• Fetching files. The Cache Manager contacts the VL Server to learn the location of the volume
containing a requested file or directory.
• Creating, viewing, and manipulating protection groups. The pts command interpreter contacts the
Protection Server when users create protection groups or request information from the Protection
Database.
• Populating the contents of the fake root.afs volume mounted at /afs (or the alternative mount point
specified in cacheinfo) when afsd is run in "-dynroot" mode. The default contents of this directory
will match the cells listed in the client CellServDB file.
• Authenticating users. Client-side authentication programs (such as an AFS-modified login utility or
the 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. This only applies to AFS cells
using the deprecated Authentication Server instead of Kerberos v5 and aklog.
The Cache Manager reads the CellServDB file into kernel memory as it initializes, and not again until the
machine next reboots or the client service restarts. 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 fs
newcell command.
If the client attempts to access an AFS cell not listed in CellServDB and afsd was started with the
-afsdb option, the Cache Manager will attempt a DNS SRV or AFSDB record lookup and dynamically add the
database server locations for that cell based on the result of the DNS query. If the -afsdb option was
not used, all AFS cells that will be accessed by a client machine must either be listed in CellServDB or
added with the fs newcell command.
The CellServDB file is in ASCII format and must reside in the /etc/openafs directory on each AFS client
machine. Use a text editor to create and maintain it.
The client version of the CellServDB file is distinct from the server version, which resides in the
/etc/openafs/server 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.
Server CellServDB
The server version of the CellServDB file lists the local cell's database server machines. These machines
run the Authentication Server (optional), Backup Server (optional), Protection Server, and Volume
Location (VL) Server (the kaserver, buserver, ptserver, and vlserver) processes, which maintain the
cell's administrative AFS databases. The initial version of the file is created with the 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 /etc/openafs/server directory on each AFS server machine.
The database server processes, in addition to the usual configuration allowing each to be elected
synchronization site and coordinate updates, can be set up as readonly database clone servers. Such
servers can never be elected as the synchronization site.
The database server processes consult the 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 CellServDB file is in ASCII format, do not use a text editor to alter it. Instead
always use the appropriate commands from the bos command suite:
• The bos addhost command to add a machine to the file.
• The bos listhosts command to display the list of machines from the file.
• The bos removehost command to remove a machine from the file.
In cells that use the Update Server to distribute the contents of the /etc/openafs/server 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 OpenAFS Quick Start chapter on installing additional server machines. Updates to the
server CellServDB will trigger reloading the cell server configurations automatically in the AFS server
processes.
CellServDB Format
Both CellServDB files have the same format:
• The first line begins at the left margin with the greater-than character (">"), followed immediately
by the cell's name without an intervening space. Optionally, a comment can follow any number of
spaces and a octothorpe ("#"), perhaps to identify the organization associated with the cell. A
variant of this allows the definition of a linked cell: after the leading (">") and cell name, a
space and a second cell name may be listed before the optional spaces, octothorpe and comment.
• Each subsequent line in the entry identifies one of the cell's database server machines, with the
indicated information in order:
• The database server machine's IP address in dotted-decimal format, optionally enclosed in square
braces ("[")("]") to define a non-voting clone.
• One or more spaces.
• An octothorpe (#), 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.
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.
For the client CellServDB, it may be desirable to make the client aware of a cell (so that it's listed by
default in /afs when the -dynroot flag to afsd is in use, for instance) without specifying the database
server machines for that cell. This can be done by including only the cell line (starting with ">") and
omitting any following database server machine lines. afsd must be configured with the -afsdb option to
use DNS SRV or AFSDB record lookups to locate database server machines. If the cell has such records and
the client is configured to use them, this configuration won't require updates to the client CellServDB
file when the IP addresses of the database server machines change.
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 CellServDB format, and so is a suitable basis for the CellServDB
file on a client machine. You can download this file from <http://grand.central.org/>.
EXAMPLES
The following example shows entries for two cells in a client CellServDB file and illustrates the
required format.
>example.com # Example Corporation
192.12.105.2 #db1.example.com
192.12.105.3 #db2.example.com
[192.12.107.3] #db3.example.com
>test.example.com example.com # Example Corporation Test Cell
192.12.108.57 #testdb1.example.com
192.12.108.55 #testdb2.example.com
The following example shows entries for two linked cells in a client CellServDB file. The a.example.com
cell is linked to the b.example.com cell.
>b.example.com # B cell
192.12.108.57 # db1.b.example.com
>a.example.com b.example.com # A cell
192.12.105.2 # db1.a.example.com
In such a setup, if a client is looking for a volume in cell a.example.com and that volume doesn't exist,
the client will try to find that volume again in cell b.example.com. The order is important. You must
list the cell being linked before the cell doing the linking.
The Windows client supports linking in two directions. The UNIX client does not allow bidirectional
linkage.
SEE ALSO
afsd(8), bos_addhost(8), bos_listhosts(8), bos_removehost(8), bos_setcellname(8), buserver(8),
fs_newcell(1), kaserver(8), klog(1), ptserver(8), vlserver(8), upclient(8), upserver(8)
OpenAFS Quick Start
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.
OpenAFS 2024-08-22 CELLSERVDB(5)