fsck does not touch your files. It is basically a front-end program that does all kinds of filesystem checks (ie. it checks the integrity of the journaling system).

If you run it interactively it will report on what it did. The checks it runs are:

** Phase 1 - Check Blocks and Sizes

** Phase 2 - Check Pathnames

** Phase 3 - Check Connectivity

** Phase 4 - Check Reference Counts

** Phase 5 - Check Cyl groups

and below this it will show a summary of

• Number of inodes in use


• Number of fragments in use


• Number of unused fragments


• Number of unused non-block fragments


• Number of unused full blocks


• Percentage of fragmentation, where: free fragments x 100 / total fragments in the file system

Besides checking inodes and blocks fsck also checks for incorrect . and .. entries and incorrect directories.

More reading material (links from wikipedia on fsck):

• adminchoice.com


• Oracle docs


• lwn.net