=head1 NAME

backup - Introduction to the backup command suite

=head1 DESCRIPTION

The commands in the B<backup> command suite are the administrative
interface to the AFS Backup System. There are several categories of
commands in the suite:

=over 4

=item *

Commands to copy data from AFS volumes to tape or a backup data file, and
to restore it to the file system: B<backup diskrestore>, B<backup dump>,
B<backup volrestore>, and B<backup volsetrestore>.

=item *

Commands to administer the records in the Backup Database: B<backup
adddump>, B<backup addhost>, B<backup addvolentry>, B<backup addvolset>,
B<backup deldump>, B<backup deletedump>, B<backup delhost>, B<backup
delvolentry>, B<backup delvolset>, B<backup dumpinfo>, B<backup
listdumps>, B<backup listhosts>, B<backup listvolsets>, B<backup
scantape>, B<backup setexp>, and B<backup volinfo>.

=item *

Commands to write and read tape labels: B<backup labeltape> and B<backup
readlabel>.

=item *

Commands to list and change the status of backup operations and the
machines performing them: B<backup jobs>, B<backup kill>, and B<backup
status>.

=item *

Commands to enter and leave interactive mode: B<backup interactive> and
B<backup quit>.

=item *

Commands to check for and repair corruption in the Backup Database:
B<backup dbverify>, B<backup restoredb>, and B<backup savedb>.

=item *

Commands to obtain help: B<backup apropos> and B<backup help>.

=back

The backup command interpreter interacts with two other processes:

=over 4

=item *

The Backup Server (B<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.

=item *

The Backup Tape Coordinator (B<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
F</usr/afs/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
F</usr/afs/backup/CFG_I<device_name>> for each Tape Coordinator records
information used to automate its operation.

=back

In addition to the standard command line interface, the B<backup> command
suite provides an I<interactive> interface, which has several useful
features described in L<backup_interactive(8)>.  Three of the commands in
the suite are available only in interactive mode: B<backup jobs>, B<backup
kill>, and B<backup quit>.

=head1 OPTIONS

The following options are available on many commands in the B<backup>
suite. The reference page for each command also lists them, but they are
described here in greater detail.

=over 4

=item B<-cell> <I<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 F</usr/vice/etc/CellServDB> file on the local machine. If
the B<-cell> argument is omitted, the command interpreter determines the
name of the local cell by reading the following in order:

=over 4

=item *

The value of the AFSCELL environment variable.

=item *

The local F</usr/vice/etc/ThisCell> file.

=back

Do not combine the B<-cell> and B<-localauth> options. A command on which
the B<-localauth> flag is included always runs in the local cell (as
defined in the server machine's local F</usr/afs/etc/ThisCell> file),
whereas a command on which the B<-cell> argument is included runs in the
specified foreign cell.

The B<-cell> argument is not available on commands issued in interactive
mode. The cell defined when the B<backup> command interpreter enters
interactive mode applies to all commands issued during the interactive
session.

=item B<-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.

=item B<-localauth>

Constructs a server ticket using the server encryption key with the
highest key version number in the local F</usr/afs/etc/KeyFile> file. The
B<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 F</usr/afs/etc/KeyFile> file.  The issuer
of a command that includes this flag must be logged on to the server
machine as the local superuser C<root>. The flag is useful for commands
invoked by an unattended application program, such as a process controlled
by the UNIX B<cron> utility or by a cron entry in the machine's
F</usr/afs/local/BosConfig> file. It is also useful if an administrator is
unable to authenticate to AFS but is logged in as the local superuser
C<root>.

Do not combine the B<-cell> and B<-localauth> options. A command on which
the B<-localauth> flag is included always runs in the local cell (as
defined in the server machine's local F</usr/afs/etc/ThisCell> file),
whereas a command on which the B<-cell> argument is included runs in the
specified foreign cell.

The B<-localauth> argument is not available on commands issued in
interactive mode. The local identity and AFS tokens with which the
B<backup> command interpreter enters interactive mode apply to all
commands issued during the interactive session.

=item B<-portoffset> <I<TC port offset>>

Specifies the port offset number of the Tape Coordinator that is to
execute the B<backup> command. The port offset number uniquely identifies
a pairing of a Tape Coordinator (B<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 B<backup> command that
involves reading or writing a tape, the backup operator must start a
B<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 B<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 F<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 C<0> through C<58510>. If the
issuer omits the argument, it defaults to C<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:

=over 4

=item *

The maximum number of dump or restore operations that can run
simultaneously is 64.

=item *

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 B<-portoffset> argument to the B<backup diskrestore>,
B<backup volrestore>, or B<backup volsetrestore> command).

=back

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
B<butc> process fails and the following error message appears at the shell
prompt:

   bind: Address already in use
   rxi_GetUDPSocket: bind failed

=back

=head1 PRIVILEGE REQUIRED

To issue any backup command that accesses the Backup Database only, the
issuer must be listed in the F</usr/afs/etc/UserList> file on every
machine where the Backup Server is running. To issue any B<backup> command
that accesses volume data, the issuer must appear in the F<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 F<UserList> file is distributed to all database server and file
server machines in the cell. See the chapter on privileged users in the
I<IBM AFS Administration Guide> for more information on this type of
privilege.

If the B<-localauth> flag is included, the user must instead be logged on
as the local superuser C<root> on the server machine where the B<backup>
command is issued.

=head1 SEE ALSO

L<BosConfig(5)>,
L<CellServDB(5)>,
L<KeyFile(5)>,
L<ThisCell(5)>,
L<UserList(5)>,
L<butc(5)>,
L<tapeconfig(5)>,
L<backup_adddump(8)>,
L<backup_addhost(8)>,
L<backup_addvolentry(8)>,
L<backup_addvolset(8)>,
L<backup_dbverify(8)>,
L<backup_deldump(8)>,
L<backup_deletedump(8)>,
L<backup_delhost(8)>,
L<backup_delvolentry(8)>,
L<backup_delvolset(8)>,
L<backup_diskrestore(8)>,
L<backup_dump(8)>,
L<backup_dumpinfo(8)>,
L<backup_help(8)>,
L<backup_interactive(8)>,
L<backup_jobs(8)>,
L<backup_kill(8)>,
L<backup_labeltape(8)>,
L<backup_listdumps(8)>,
L<backup_listhosts(8)>,
L<backup_listvolsets(8)>,
L<backup_quit(8)>,
L<backup_readlabel(8)>,
L<backup_restoredb(8)>,
L<backup_savedb(8)>,
L<backup_scantape(8)>,
L<backup_setexp(8)>,
L<backup_status(8)>,
L<backup_volinfo(8)>,
L<backup_volrestore(8)>,
L<backup_volsetrestore(8)>,
L<buserver(8)>,
L<butc(8)>

=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.
