pg\_checksums

pg\_checksums

1

Application

pg\_checksums

enable, disable or check data checksums in a

PostgreSQL

database cluster

pg\_checksums

option

-D

\--pgdata

datadir

Description {#r1-app-pg_checksums-1}
===========

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`.

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 [???](#app-pgrewind)), 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.
