[rhelv6-list] fsck -n always showing errors

[Collins, Kevin]

From ‘man fsck’:

       -N     Don't execute, just show what would be done.

and:

       Options  to  different  filesystem-specific  fsck's  are not standardized.  If in doubt, please consult the man
       pages of the filesystem-specific checker.  Although not guaranteed, the following options are supported by most
       file system checkers:

…
…

       -n     For some filesystem-specific checkers, the -n option will cause the fs-specific fsck to avoid attempting
              to repair any problems, but simply report such problems to stdout.  This is however  not  true  for  all
              filesystem-specific  checkers.   In particular, fsck.reiserfs(8) will not report any corruption if given
              this option.  fsck.minix(8) does not support the -n option at all.

From ‘man e2fsck’:

       -n     Open  the filesystem read-only, and assume an answer of 'no' to all questions.  Allows e2fsck to be used
              non-interactively.  This option may not be specified at the same time as the -p or -y options.

Kevin

From: rhelv6-list-bounces at redhat.com [mailto:rhelv6-list-bounces at redhat.com] On Behalf Of francis picabia
Sent: Friday, December 22, 2017 7:05 AM
To: Red Hat Enterprise Linux 6 (Santiago) discussion mailing-list <rhelv6-list at redhat.com>
Subject: [**EXTERNAL**] Re: [rhelv6-list] fsck -n always showing errors


On Thu, Dec 21, 2017 at 2:48 PM, Tim Mooney <Tim.Mooney at ndsu.edu<mailto:Tim.Mooney at ndsu.edu>> wrote:
In regard to: rhelv6-list Digest, Vol 76, Issue 1, rhelv6-list-request at redh...:
This isn't something we routinely look at, but after
a couple of VMware systems showing scsi errors, I noticed almost
every Redhat 6 system will show some disk errors from
something like fsck -n / or same on /var

# fsck -n /
fsck from util-linux-ng 2.17.2
e2fsck 1.41.12 (17-May-2010)
Warning!  /dev/sda1 is mounted.

There's your problem.  Don't run fsck on a mounted filesystem.  Even
with -n, it just shows you false positives.

Do some web searching for

        fsck on a mounted filesystem

to understand why.

Well, I think they make the -n/-N flag in fsck for some purpose other than don't do it.
It is designed to be run on a system to check it without modifying.
My conclusion is it is only useful for seeing an error such as orphaned
inodes which are persistent across multiple runs of fsck -n
If there are other checksums and such that don't seem correct, that would be expected
on a live filesystem.
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