Using Global File System Checking

Describes how to use the gfsck command to check and repair filesystem errors.

You can use the gfsck (global filesystem check) command to perform a consistency check and repair operation on a volume or volume snapshot, including the following entities:

All cross-container links (for example, from file to filelet, or from table to tablets)
The tabletmap key range
The attributes of filelet (uid/gid/mode)

This command identifies the unreachable files, directories, and tables in the volume, and moves them to /lost+found to be repaired. It also identifies and fixes any unreachable DB inodes or dangling pointers to lost inodes.

Take the affected storage pools offline by running the mrconfig sp offline command.
For example:
```
/opt/mapr/server/mrconfig sp offline /dev/sdc
```
Execute the fsck command on the storage pools or disks.
Bring the storage pools back online by running the mrconfig sp online command.
For example:
```
mrconfig sp online /dev/sdc
```
Run the gfsck command on the affected volumes, or snapshots, with the appropriate options.
If there are alarms, such as DataUnavailableAlarm or DataUnderReplicatedAlarm, do not run the gfsck command with the -r (--repair) option. Running the gfsck command with the -r (--repair) option, might result in data loss. If necessary, first run gfsck without the -r (--repair) option, and attempt to repair only after analyzing the command output.