PG_BASEBACKUP(1) PostgreSQL 9.1.9 Documentation PG_BASEBACKUP(1)NAME
pg_basebackup - take a base backup of a PostgreSQL cluster
SYNOPSIS
pg_basebackup [option...]
DESCRIPTION
pg_basebackup is used to take base backups of a running PostgreSQL
database cluster. These are taken without affecting other clients to
the database, and can be used both for point-in-time recovery (see
Section 24.3, “Continuous Archiving and Point-in-Time Recovery (PITR)”,
in the documentation) and as the starting point for a log shipping or
streaming replication standby servers (see Section 25.2, “Log-Shipping
Standby Servers”, in the documentation).
pg_basebackup makes a binary copy of the database cluster files, while
making sure the system is automatically put in and out of backup mode
automatically. Backups are always taken of the entire database cluster,
it is not possible to back up individual databases or database objects.
For individual database backups, a tool such as pg_dump(1) must be
used.
The backup is made over a regular PostgreSQL connection, and uses the
replication protocol. The connection must be made with a user having
REPLICATION permissions (see Section 20.2, “Role Attributes”, in the
documentation), and the user must be granted explicit permissions in
pg_hba.conf. The server must also be configured with max_wal_senders
set high enough to leave at least one session available for the backup.
There can be multiple pg_basebackups running at the same time, but it
is better from a performance point of view to take only one backup, and
copy the result.
OPTIONS
The following command-line options control the location and format of
the output.
-D directory, --pgdata=directory
Directory to write the output to.
When the backup is in tar mode, and the directory is specified as -
(dash), the tar file will be written to stdout.
This parameter is required.
-F format, --format=format
Selects the format for the output. format can be one of the
following:
p, plain
Write the output as plain files, with the same layout as the
current data directory and tablespaces. When the cluster has no
additional tablespaces, the whole database will be placed in
the target directory. If the cluster contains additional
tablespaces, the main data directory will be placed in the
target directory, but all other tablespaces will be placed in
the same absolute path as they have on the server.
This is the default format.
t, tar
Write the output as tar files in the target directory. The main
data directory will be written to a file named base.tar, and
all other tablespaces will be named after the tablespace OID.
If the value - (dash) is specified as target directory, the tar
contents will be written to standard output, suitable for
piping to for example gzip. This is only possible if the
cluster has no additional tablespaces.
-x, --xlog
Includes the required transaction log files (WAL files) in the
backup. This will include all transaction logs generated during the
backup. If this option is specified, it is possible to start a
postmaster directly in the extracted directory without the need to
consult the log archive, thus making this a completely standalone
backup.
Note
The transaction log files are collected at the end of the
backup. Therefore, it is necessary for the wal_keep_segments
parameter to be set high enough that the log is not removed
before the end of the backup. If the log has been rotated when
it's time to transfer it, the backup will fail and be unusable.
-z, --gzip
Enables gzip compression of tar file output, with the default
compression level. Compression is only available when using the tar
format.
-Z level, --compress=level
Enables gzip compression of tar file output, and specifies the
compression level (1 through 9, 9 being best compression).
Compression is only available when using the tar format.
The following command-line options control the generation of the backup
and the running of the program.
-c fast|spread, --checkpoint=fast|spread
Sets checkpoint mode to fast or spread (default).
-l label, --label=label
Sets the label for the backup. If none is specified, a default
value of pg_basebackup base backup will be used.
-P, --progress
Enables progress reporting. Turning this on will deliver an
approximate progress report during the backup. Since the database
may change during the backup, this is only an approximation and may
not end at exactly 100%. In particular, when WAL log is included in
the backup, the total amount of data cannot be estimated in
advance, and in this case the estimated target size will increase
once it passes the total estimate without WAL.
When this is enabled, the backup will start by enumerating the size
of the entire database, and then go back and send the actual
contents. This may make the backup take slightly longer, and in
particular it will take longer before the first data is sent.
-v, --verbose
Enables verbose mode. Will output some extra steps during startup
and shutdown, as well as show the exact file name that is currently
being processed if progress reporting is also enabled.
The following command-line options control the database connection
parameters.
-h host, --host=host
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. The default is taken from the
PGHOST environment variable, if set, else a Unix domain socket
connection is attempted.
-p port, --port=port
Specifies the TCP port or local Unix domain socket file extension
on which the server is listening for connections. Defaults to the
PGPORT environment variable, if set, or a compiled-in default.
-U username, --username=username
User name to connect as.
-w, --no-password
Never issue a password prompt. If the server requires password
authentication and a password is not available by other means such
as a .pgpass file, the connection attempt will fail. This option
can be useful in batch jobs and scripts where no user is present to
enter a password.
-W, --password
Force pg_basebackup to prompt for a password before connecting to a
database.
This option is never essential, since pg_basebackup will
automatically prompt for a password if the server demands password
authentication. However, pg_basebackup will waste a connection
attempt finding out that the server wants a password. In some cases
it is worth typing -W to avoid the extra connection attempt.
Other, less commonly used, parameters are also available:
-V, --version
Print the pg_basebackup version and exit.
-?, --help
Show help about pg_basebackup command line arguments, and exit.
ENVIRONMENT
This utility, like most other PostgreSQL utilities, uses the
environment variables supported by libpq (see Section 31.13,
“Environment Variables”, in the documentation).
NOTES
The backup will include all files in the data directory and
tablespaces, including the configuration files and any additional files
placed in the directory by third parties. Only regular files and
directories are allowed in the data directory, no symbolic links or
special device files.
The way PostgreSQL manages tablespaces, the path for all additional
tablespaces must be identical whenever a backup is restored. The main
data directory, however, is relocatable to any location.
EXAMPLES
To create a base backup of the server at mydbserver and store it in the
local directory /usr/local/pgsql/data:
$ pg_basebackup -h mydbserver -D /usr/local/pgsql/data
To create a backup of the local server with one compressed tar file for
each tablespace, and store it in the directory backup, showing a
progress report while running:
$ pg_basebackup -D backup -Ft -z -P
To create a backup of a single-tablespace local database and compress
this with bzip2:
$ pg_basebackup -D - -Ft | bzip2 > backup.tar.bz2
(This command will fail if there are multiple tablespaces in the
database.)
SEE ALSOpg_dump(1)PostgreSQL 9.1.9 2013-04-01 PG_BASEBACKUP(1)