pg_checksums - Man Page

• Check data checksums in a database cluster: pg_checksums [-D|--pgdata] path/to/data
• Enable data checksums in a database cluster: pg_checksums [-e|--enable] [-D|--pgdata] path/to/data
• Disable data checksums in a database cluster: pg_checksums [-d|--disable] [-D|--pgdata] path/to/data
• Check data checksums with verbose output: pg_checksums [-v|--verbose] [-D|--pgdata] path/to/data
• Check data checksums showing progress: pg_checksums [-P|--progress] [-D|--pgdata] path/to/data
• Display help: pg_checksums [-?|--help]

tldr.sh

pg_checksums [option...] [[-D | --pgdata]datadir]

pg_checksums checks, enables or disables data checksums in a PostgreSQL cluster​. The server must be shut down cleanly before running pg_checksums​. When verifying checksums, the exit status is zero if there are no checksum errors, and nonzero if at least one checksum failure is detected​. When enabling or disabling checksums, the exit status is nonzero if the operation failed​.

When verifying checksums, every file in the cluster is scanned​. When enabling checksums, each relation file block with a changed checksum is rewritten in-place​. Disabling checksums only updates the file pg_control​.

The following command-line options are available:

-D directory

--pgdata=directory

Specifies the directory where the database cluster is stored​.

-c

--check

Checks checksums​. This is the default mode if nothing else is specified​.

-d

--disable

Disables checksums​.

-e

--enable

Enables checksums​.

-f filenode

--filenode=filenode

Only validate checksums in the relation with filenode filenode​.

-N

--no-sync

By default, pg_checksums will wait for all files to be written safely to disk​. This option causes pg_checksums to return without waiting, which is faster, but means that a subsequent operating system crash can leave the updated data directory corrupt​. Generally, this option is useful for testing but should not be used on a production installation​. This option has no effect when using --check​.

-P

--progress

Enable progress reporting​. Turning this on will deliver a progress report while checking or enabling checksums​.

-v

--verbose

Enable verbose output​. Lists all checked files​.

-V

--version

Print the pg_checksums version and exit​.

-?

--help

Show help about pg_checksums command line arguments, and exit​.

PGDATA

Specifies the directory where the database cluster is stored; can be overridden using the -D option​.

PG_COLOR

Specifies whether to use color in diagnostic messages​. Possible values are always, auto and never​.

Enabling checksums in a large cluster can potentially take a long time​. During this operation, the cluster or other programs that write to the data directory must not be started or else data loss may occur​.

When using a replication setup with tools which perform direct copies of relation file blocks (for example pg_rewind(1)), enabling or disabling checksums can lead to page corruptions in the shape of incorrect checksums if the operation is not done consistently across all nodes​. When enabling or disabling checksums in a replication setup, it is thus recommended to stop all the clusters before switching them all consistently​. Destroying all standbys, performing the operation on the primary and finally recreating the standbys from scratch is also safe​.

If pg_checksums is aborted or killed while enabling or disabling checksums, the cluster's data checksum configuration remains unchanged, and pg_checksums can be re-run to perform the same operation​.