PG_BASEBACKUP(1) PostgreSQL 9.2.7 Documentation PG_BASEBACKUP(1)
pg_basebackup - take a base backup of a PostgreSQL cluster
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
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
The backup is made over a regular PostgreSQL connection, and uses the replication
protocol. The connection must be made with a superuser or a user having REPLICATION
permissions (see Section 20.2, "Role Attributes", in the documentation), and pg_hba.conf
must explicitly permit the replication connection. 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.
pg_basebackup can make a base backup from not only the master but also the standby. To
take a backup from the standby, set up the standby so that it can accept replication
connections (that is, set max_wal_senders and hot_standby, and configure host-based
authentication). You will also need to enable full_page_writes on the master.
Note that there are some limitations in an online backup from the standby:
o The backup history file is not created in the database cluster backed up.
o There is no guarantee that all WAL files required for the backup are archived at the
end of backup. If you are planning to use the backup for an archive recovery and want
to ensure that all required files are available at that moment, you need to include
them into the backup by using -x option.
o If the standby is promoted to the master during online backup, the backup fails.
o All WAL records required for the backup must contain sufficient full-page writes,
which requires you to enable full_page_writes on the master and not to use a tool like
pg_compresslog as archive_command to remove full-page writes from WAL files.
The following command-line options control the location and format of the output.
-D directory, --pgdata=directory
Directory to write the output to. pg_basebackup will create the directory and any
parent directories if necessary. The directory may already exist, but it is an error
if the directory already exists and is not empty.
When the backup is in tar mode, and the directory is specified as - (dash), the tar
file will be written to stdout.
This option is required.
-F format, --format=format
Selects the format for the output. format can be one of the following:
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.
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.
Using this option is equivalent of using -X with method fetch.
-X method, --xlog-method=method
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.
The following methods for collecting the transaction logs are supported:
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.
Stream the transaction log while the backup is created. This will open a second
connection to the server and start streaming the transaction log in parallel while
running the backup. Therefore, it will use up two slots configured by the
max_wal_senders parameter. As long as the client can keep up with transaction log
received, using this mode requires no extra transaction logs to be saved on the
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
The following command-line options control the generation of the backup and the running of
-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.
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
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.
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.
-s interval, --status-interval=interval
Specifies the number of seconds between status packets sent back to the server. This
is required when streaming the transaction log (using --xlog=stream) if replication
timeout is configured on the server, and allows for easier monitoring. A value of zero
disables the status updates completely. The default value is 10 seconds.
-U username, --username=username
User name to connect as.
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.
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 options are also available:
Print the pg_basebackup version and exit.
Show help about pg_basebackup command line arguments, and exit.
This utility, like most other PostgreSQL utilities, uses the environment variables
supported by libpq (see Section 31.14, "Environment Variables", in the documentation).
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.
To create a base backup of the server at mydbserver and store it in the local directory
$ 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.)
PostgreSQL 9.2.7 2014-02-17 PG_BASEBACKUP(1)