lt_checksums — enable, disable or check data checksums in a LightDB database cluster
lt_checksums [option...] [[ -D | --pgdata ]datadir]
lt_checksums checks, enables or disables data checksums in a LightDB cluster. The server must be shut down cleanly before running lt_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 lt_control.
The following command-line options are available:
-D directory--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.
-f filenode--filenode=filenode
Only validate checksums in the relation with filenode
filenode.
-N--no-sync
By default, lt_checksums will wait for all files
to be written safely to disk. This option causes
lt_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--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 lt_checksums version and exit.
-?--helpShow help about lt_checksums command line arguments, and exit.
LTDATA
Specifies the directory where the database cluster is
stored; can be overridden using the -D option.
LT_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 lt_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 lt_checksums is aborted or killed while enabling or disabling checksums, the cluster's data checksum configuration remains unchanged, and lt_checksums can be re-run to perform the same operation.