Ubuntu Manpage: pg_backup_ctl - Utility to backup and recover a running PostgresSQL database server

NAME

       pg_backup_ctl - Utility to backup and recover a running PostgresSQL database server

SYNOPSIS

       pg_backup_ctl [options...]

DESCRIPTION

       pg_backup_ctl  is  a  tool  to  simplify  the  steps needed to make a full transaction log
       archival Backup of PostgreSQL clusters. All steps performed by this script can  also  done
       manually. See http://www.postgresql.org/docs/9.2/interactive/continuous-archiving.html for
       details. Furthermore this script implements several functions to prepare for backups using
       LVM-Snapshots.

       This script supports PostgreSQL 8.3 and above.

       While  setup  pg_backup_ctl  will  make some modifications to postgresql.conf specified in
       running_config. To work correctly 3 options will be set:
           - archive_command used to copy archived WAL files to archivedir/log/ directory
           - wal_level will be set to archive, if isn't already at archive or hot-standby.
           - archive_mode will be set to on If  these  modifications  aren't  already  done,  the
       server needs to restart after setup to take over these changes.

       pg_backup_ctl  should  be run as postgres user (or any other user that runs the postgresql
       daemon). In addition, if the LVM features where  used,  the  user  needs  the  appropriate
       permissions  (add  sudo  execution  privileges  for  postgres  to  the following commands:
       lvcreate, lvremove, lvdisplay, mount, lvdisplay)

MODES

setup
Prepare server for transaction log archival and setup the environment.

This adjusts the server configuration file as required and reloads the server
configuration. However, since PostgreSQL 8.3 the script needs to set the archive_mode
explicitly to on, forcing the administrator to restart the PostgreSQL instance (if
required). After a restart (assuming there is database activity), you should be seeing
files appearing in /var/lib/pgsql/backup/log.

basebackup
Perform a base backup of the currently running PostgreSQL cluster.

You should run this command from a cron job (mind the postgres user) once a night.
(Once a week or other intervals are also conceivable but will lead to huge recovery
times for your data volume.)

You could replace this step by taking a file system snapshot. This might save space
and time but would otherwise be functionally equivalent. You can also alter the
script accordingly. Look into the line that calls the tar program.

lvmbasebackup
Perform a base backup using LVM snapshot. (Requires -L, -M, -n, -N)

create-lvmsnapshot
Create an LVM snapshot for an external backup command like bacula. (Requires -L, -M,
-n, -N)

rsyncbackup
Perform a basebackup with rsync.

This command requires rsync accessible via PATH. Backups performed with rsyncbackup
will save disk space between multiple runs for unchanged files, since they are just
hardlinked. See the --link-dest parameter of the rsync command.

streambackup
Perform a streaming basebackup.

This command requires PostgreSQL 9.1 and above and pg_basebackup accessible via PATH.
The server should be configured to allow streaming replication connections.

remove-lvmsnapshot
Remove an LVM snapshot created with create-lvmsnapshot.

restore basebackup
Restores the specified basebackup into the specified directory by the -D parameter.

The directory must already exists and be empty. If the directory, wich is specified as
target location, isn't empty pg_backup_ctl will refuse it as target.

The destination directory will also contain a generated recovery.conf, suitable to
start a PostgreSQL instance for recovery immediately.

It is still possible to do the recovery process completely manually. The recovery
process is detailed in the documentation.

currentbackup
Backup the current WAL file. This command should be called from a cronjob.

cleanup [ filename | xlog | +[1-9]* ]
Remove old WAL files after new base backup. This command sould also run by a cron job.

One typically runs this command from a cron job once a minute (whatever the desired
backup frequency) your data volume will cause log segments to fill up on the order of
minutes anyway, so this step can then be omitted.

This will only clean up old log segments. Old base backups have to be removed
manually.

It is possible to specify the base backup filename filename, wich WAL files should be
kept at least or the WAL file xlog. If a positive number greater than zero is
specified, the cleanup command will treat it as its retention policy and keep at least
this number of base backup files. Please note that the latter form of the cleanup
command will delete all outdated base backups as well whereas the two forms of cleanup
invoke with filename will delete the WAL files only.

If no argument is specified, cleanup will remove all WAL files except those wich are
required by the latest base backup.

ls[+]
Lists available base backups and there size in the current archive. When issued with
+, the ls command will examine the WAL archive and the minimum WAL segment file,
required to use the backup to perform a full recovery.

OPTIONS

The following command-line options control actions done by pg_backup_ctl.

-A archivedir
Directory with will contain the backup-files. This parameter is required at all
actions. It will also contain configuration and history files needed for all actions,
except setup.

-D datadir
PostgresSQL data directory. If PostgreSQL is running this parameter isn't used and
will come from PostgreSQL running_configuration.

-T TABLESPACE
Target directory for tablespace location during restore (replaces the original
symlinks in the base backup, but places all tablespaces into one directory).

-m
Take care of old archive log files, archive these files before deleting them.

-z
Compression. Use gzip to compress archived WAL segments.

-L lvm-size
Determines the buffer size for an LVM snapshot.

-M volume
LVM volume identifier to create the snapshot on. Needed for LVM-Backup.

-n name
LVM snapshot volume name. Needed for LVM-Backup. The backup_lable will be named after
it.

-N lvm-data-dir
PostgreSQL DATADIR relative to partition (i.e the path to DATADIR inside the LVM
snapshot).

-o mount-options
Additional options passed to LVM snapshot mount.

-h hostname
Server hostname that running PostgreSQL. Specifies the host name of the machine on
which the server is running. If the value begins with a slash, it is used as the
directory for the Unix domain socket. (See pgsql(1) for details)

-p port
Specifies the TCP port or local Unix domain socket file extension on which the server
is listening for connections. (See pgsql(1) for details)

-M username
User name to connect as.

EXAMPLES

       To setup the environment and PostgreSQL configuration settings for further cluster backups
       at /mnt/backup/pgsql:

           $ pg_backup_ctl -A /mnt/backup/pgsql setup

       To do a base backup (Note: setup the environment is required):

           $ pg_backup_ctl -A /mnt/backup/pgsql basebackup

       To do a streaming base backup backup (Note: setup  the  environment  and  configuring  the
       PostgreSQL database server to allow streaming replication is required):

           $ pg_backup_ctl -A /mnt/backup/pgsql streambackup

       To do a base backup backup with rsync (Note: setup the environment is required):

           $ pg_backup_ctl -A /mnt/backup/pgsql rsyncbackup

       To copy the current log segment(s):

           $ pg_backup_ctl -A /mnt/backup/pgsql currentbackup

       To show up the backups that are available:

           $ pg_backup_ctl -A /mnt/backup/pgsql ls+

       To  recover  a  base  backup  (e.g.  basebackup_2013-01-04T1517.tar.gz)  to  the directory
       /recover/pgsql (the server may not run):

           $    pg_backup_ctl     -A     /mnt/backup/pgsql     -D     /recovery/pgsql     restore
           basebackup_2013-01-04T1517.tar.gz

           $ pg_ctl start -D /recovery/pgsql

CAVEATS

       pg_backup_ctl  internally  protects  itself  against  concurrent  execution with the flock
       command line tool. This places a lock file into the archive directory, which will hold  an
       exclusive  lock on it to prevent another pg_backup_ctl to concurrently modify the archive.
       This doesn't work on network filesystems like SMBFS or CIFS, especially when mounted  from
       a Windows(tm) server. In this case you should use the -l option to place the lockfile into
       a directory on a local filesystem.  Older distributions doesn't  have  the  flock  command
       line tool, but it's possible to just comment out the locking subscripts.