Checking Mounted Filesystems

Checking Mounted Filesystems

If you cannot shut down the system and cannot unmount the filesystem, but you need to perform the check immediately, you can run fsck in "no-write" mode. The fsck command checks the filesystem, but makes no changes and does not repair inconsistencies.

For example, the following command invokes fsck in no-write mode:

# fsck -n /dev/usr

If any inconsistencies are found, they are not repaired. You must run fsck again without the -n flag to repair any problems. The benefit of this procedure is that you should be able to gauge the severity of the problems with your filesystem. The disadvantage of this procedure is that fsck may complain about inconsistencies that don't really exist (because the filesystem is active).