NAME

       pg_checksums - enable, disable or check data checksums in a PostgreSQL database cluster

SYNOPSIS

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

DESCRIPTION

       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, every file in
       the cluster is rewritten in-place. Disabling checksums only updates the file pg_control.

OPTIONS

       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.

ENVIRONMENT

       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.

NOTES

       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.