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NAME
backup - Introduction to the backup command suite
DESCRIPTION
The commands in the backup command suite are the administrative interface to the AFS Backup System. There
are several categories of commands in the suite:
• Commands to copy data from AFS volumes to tape or a backup data file, and to restore it to the file
system: backup diskrestore, backup dump, backup volrestore, and backup volsetrestore.
• Commands to administer the records in the Backup Database: backup adddump, backup addhost, backup
addvolentry, backup addvolset, backup deldump, backup deletedump, backup delhost, backup delvolentry,
backup delvolset, backup dumpinfo, backup listdumps, backup listhosts, backup listvolsets, backup
scantape, backup setexp, and backup volinfo.
• Commands to write and read tape labels: backup labeltape and backup readlabel.
• Commands to list and change the status of backup operations and the machines performing them: backup
jobs, backup kill, and backup status.
• Commands to enter and leave interactive mode: backup interactive and backup quit.
• Commands to check for and repair corruption in the Backup Database: backup dbverify, backup
restoredb, and backup savedb.
• Commands to obtain help: backup apropos and backup help.
• A command to display the OpenAFS command suite version: backup version.
The backup command interpreter interacts with two other processes:
• The Backup Server (buserver) process. It maintains the Backup Database, which stores most of the
administrative information used by the Backup System. In the standard configuration, the Backup
Server runs on each database server machine in the cell, and uses AFS's distributed database
technology, Ubik, to synchronize its copy of the database with the copies on the other database
server machines.
• The Backup Tape Coordinator (butc) process. A separate instance of the process controls each tape
device or backup data file used to dump or restore data. The Tape Coordinator runs on a Tape
Coordinator machine, which is an AFS server or client machine that has one or more tape devices
attached, or has sufficient disk space to accommodate one or more backup data files on its local
disk.
Each Tape Coordinator must be registered in the Backup Database and in the
/var/lib/openafs/backup/tapeconfig configuration file on the Tape Coordinator machine's local disk,
and information in the two places must be consistent for proper Backup System performance. The
optional /var/lib/openafs/backup/CFG_device_name for each Tape Coordinator records information used
to automate its operation.
In addition to the standard command line interface, the backup command suite provides an interactive
interface, which has several useful features described in backup_interactive(8). Three of the commands
in the suite are available only in interactive mode: backup jobs, backup kill, and backup quit
OPTIONS
The following options are available on many commands in the backup suite. The reference page for each
command also lists them, but they are described here in greater detail.
-cell <cell name>
Names the cell in which to run the command. It is acceptable to abbreviate the cell name to the
shortest form that distinguishes it from the other entries in the /etc/openafs/CellServDB file on the
local machine. If the -cell argument is omitted, the command interpreter determines the name of the
local cell by reading the following in order:
• The value of the AFSCELL environment variable.
• The local /etc/openafs/ThisCell file.
Do not combine the -cell and -localauth options. A command on which the -localauth flag is included
always runs in the local cell (as defined in the server machine's local /etc/openafs/server/ThisCell
file), whereas a command on which the -cell argument is included runs in the specified foreign cell.
The -cell argument is not available on commands issued in interactive mode. The cell defined when the
backup command interpreter enters interactive mode applies to all commands issued during the
interactive session.
-help
Prints a command's online help message on the standard output stream. Do not combine this flag with
any of the command's other options; when it is provided, the command interpreter ignores all other
options, and only prints the help message.
-localauth
Constructs a server ticket using the server encryption key with the highest key version number in the
local /etc/openafs/server/KeyFile or /etc/openafs/server/KeyFileExt file. The backup command
interpreter presents the ticket, which never expires, to the Backup Server, Volume Server and Volume
Location (VL) Server during mutual authentication.
Use this flag only when issuing a command on a server machine; client machines do not usually have a
/etc/openafs/server/KeyFile or /etc/openafs/server/KeyFileExt file. The issuer of a command that
includes this flag must be logged on to the server machine as the local superuser "root". The flag is
useful for commands invoked by an unattended application program, such as a process controlled by the
UNIX cron utility or by a cron entry in the machine's /etc/openafs/BosConfig file. It is also useful
if an administrator is unable to authenticate to AFS but is logged in as the local superuser "root".
Do not combine the -cell and -localauth options. A command on which the -localauth flag is included
always runs in the local cell (as defined in the server machine's local /etc/openafs/server/ThisCell
file), whereas a command on which the -cell argument is included runs in the specified foreign cell.
The -localauth argument is not available on commands issued in interactive mode. The local identity
and AFS tokens with which the backup command interpreter enters interactive mode apply to all
commands issued during the interactive session.
-nobutcauth
Prior to the fix for OPENAFS-SA-2018-001, butc did not allow incoming connections to be
authenticated. As part of that fix, backup was modified to authenticate to the butc services when
possible, but a backup utility with the security fix will not interoperate with a butc that lacks the
fix unless this option is passed, which forces the use of unauthenticated connections to the butc.
Use of this option is strongly disrecommended, and it is provided only for backwards compatibility in
environments where backup and butc communicate over a secure network environment that denies access
to untrusted parties.
-portoffset <TC port offset>
Specifies the port offset number of the Tape Coordinator that is to execute the backup command. The
port offset number uniquely identifies a pairing of a Tape Coordinator (butc) process and tape device
or backup data file.
The backup command interpreter and Tape Coordinator process communicate via a UDP socket, or port.
Before issuing a backup command that involves reading or writing a tape, the backup operator must
start a butc process that controls the appropriate tape device and listens for requests sent to its
port number. If a Backup System machine has multiple tape devices attached, they can perform backup
operations simultaneously because each device has its own associated butc process and port offset
number.
The Backup System associates a tape capacity and file mark size with each port offset (as defined in
the tapeconfig file). For a compressing tape device, the capacity and file mark values differ for
compression and non-compression modes, so the two modes have distinct port offset numbers.
The Backup Database can store up to 58,511 port offsets, so the legal values for this argument are
the integers 0 through 58510. If the issuer omits the argument, it defaults to 0. (The limit of
58,511 port offsets results from the fact that UDP socket numbers are identified by a 16-bit integer,
and the lowest socket number used by the Backup System is 7025. The largest number that a 16-bit
integer can represent is 65,535. Subtracting 7,025 yields 58,510. The addition of port offset 0
(zero) increases the maximum to 58,511.)
Although it is possible to define up to 58,511 port offset numbers for a cell, it is not possible to
run 58,511 tape devices simultaneously, due to the following limits:
• The maximum number of dump or restore operations that can run simultaneously is 64.
• The maximum number of tape devices that can work together on a restore operation is 128 (that is
the maximum number of values that can be provided for the -portoffset argument to the backup
diskrestore, backup volrestore, or backup volsetrestore command).
The Backup System does not reserve UDP sockets. If another application is already using the Tape
Coordinator's socket when it tries to start, the butc process fails and the following error message
appears at the shell prompt:
bind: Address already in use
rxi_GetUDPSocket: bind failed
PRIVILEGE REQUIRED
To issue any backup command that accesses the Backup Database only, the issuer must be listed in the
/etc/openafs/server/UserList file on every machine where the Backup Server is running. To issue any
backup command that accesses volume data, the issuer must appear in the UserList file on every Backup
Server machine, every Volume Location (VL) Server machine, and every file server machine that houses
affected volumes. By convention, a common UserList file is distributed to all database server and file
server machines in the cell. See the chapter on privileged users in the OpenAFS Administration Guide for
more information on this type of privilege.
If the -localauth flag is included, the user must instead be logged on as the local superuser "root" on
the server machine where the backup command is issued.
SEE ALSO
BosConfig(5), CellServDB(5), KeyFile(5), KeyFileExt(5), ThisCell(5), UserList(5), butc(5), tapeconfig(5),
backup_adddump(8), backup_addhost(8), backup_addvolentry(8), backup_addvolset(8), backup_apropos(8),
backup_dbverify(8), backup_deldump(8), backup_deletedump(8), backup_delhost(8), backup_delvolentry(8),
backup_delvolset(8), backup_diskrestore(8), backup_dump(8), backup_dumpinfo(8), backup_help(8),
backup_interactive(8), backup_jobs(8), backup_kill(8), backup_labeltape(8), backup_listdumps(8),
backup_listhosts(8), backup_listvolsets(8), backup_quit(8), backup_readlabel(8), backup_restoredb(8),
backup_savedb(8), backup_scantape(8), backup_setexp(8), backup_status(8), backup_volinfo(8),
backup_volrestore(8), backup_volsetrestore(8), buserver(8), butc(8)
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 2025-05-19 BACKUP(8)