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 when enabling or disabling checksums, while verifying checksums
       can be done online. 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. 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. Progress reporting can also be triggered by the
           <signal>SIGUSR1</signal> signal.

       --max-rate=rate
           Set a maximum I/O rate (in MB/s) while checking or enabling checksums.

       -v
       --verbose
           Enable verbose output. Lists all checked files.

       --debug
           Enable debug output.

       -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 diagnostics messages. Possible values are always,
           auto, 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), 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.