Ubuntu :: Can Running E2fsck On Live System Cause Errors ?

We have an old server running, and I decided to run fsck.ext3 -n on the disk to check it (while it was running). Turns out it reports lots of errors - not a good thing.

The weird thing is that when booting up a rescue cd and running fsck.ext3 on it, it says there are no problems with it. The filesystem is marked clean. Forcing a check with -f turns up nothing.

Now, when booting it from disk, fsck complains about an unclean file system that has not been checked for like 50000 days (obviously an error). Running e2fsck -n /dev/sda2 turns up errors again - not necessarily the same ones as the last time.

This makes me wonder: Can running e2fsck on a mounted file system cause errors? I ran with -n which is not supposed to do anything, just doing a read-only check. On the other hand, I heard checking a live file system might throw erros since the files being checked might change while bign checked, thus causing false positives.

Can the old version of e2fstools (1.38, approx 2005) mean non-existing errors are shown? Both the rescue cd and the system use this version.

In any case - why would the file system report errors on boot-up when the rescue cd just said it was ok? It should have been marked clean by now.

For laughs, I shut down the system and booted Knoppix which has a quite recent version (1.41.12, May 2010) of e2fstools. It showed no errors on the file system.

What do you think - are there errors or not on the file system?

The system is actually running Suse, but this is not about Suse specific things - just general Linux tools. And I use Ubuntu personally.