pg_checksums
pg_checksums — enable, disable or check data checksums in a Postgres Pro database cluster
Synopsis
pg_checksums [option...] [[ -D | --pgdata ]datadir]
Description #
pg_checksums checks, enables or disables data checksums in a Postgres Pro 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:
-Ddirectory--pgdata=directorySpecifies the directory where the database cluster is stored.
-c--checkChecks checksums. This is the default mode if nothing else is specified.
-d--disableDisables checksums.
-e--enableEnables checksums.
-ffilenode--filenode=filenodeOnly validate checksums in the relation with filenode
filenode.-N--no-syncBy default,
pg_checksumswill wait for all files to be written safely to disk. This option causespg_checksumsto 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--progressEnable progress reporting. Turning this on will deliver a progress report while checking or enabling checksums.
-v--verboseEnable verbose output. Lists all checked files.
-V--versionPrint the pg_checksums version and exit.
-?--helpShow help about pg_checksums command line arguments, and exit.
Environment
PGDATASpecifies the directory where the database cluster is stored; can be overridden using the
-Doption.PG_COLORSpecifies whether to use color in diagnostic messages. Possible values are
always,autoandnever.
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.