[Ubuntu-users] fsck shows errors on main partition only when mounted

[K. Frank]

Hi Mark and Colin -

On Tue, Nov 16, 2010 at 11:38 AM, Mark <mhullrich at gmail.com> wrote:
> On Tue, Nov 16, 2010 at 7:51 AM, Colin Law <clanlaw at googlemail.com> wrote:
>> On 16 November 2010 15:10, K. Frank <kfrank29.c at gmail.com> wrote:
>>> Hello All -
>>>
>>> I have just installed ubuntu on a former windows machine whose
>>> os had become corrupted, and fsck reports disk errors.
>>>
>>> Should I care, and how can I fix this?
>>>
>> I don't think it is valid to run fsck on a mounted drive.

Does this mean that even in "read-only" mode (-n) fsck assumes,
in effect, that the partition is not mounted, and therefore errors it
reports can be false positives?

> When a drive is mounted, the data on it changes frequently, especially
> if it's the system drive.  You're asking for trouble if you do this.

Am I asking for trouble if I use the -n option?  I am under the impression
that I can run fsck -n to my heart's content on mounted file systems
completely safely (if perhaps not usefully).  Is this not correct?

> However, what are you attempting to do using the -n option?  That won't help.

The idea, if I understand correctly, is that -n tells fsck not to attempt to
fix anything (or otherwise modify anything), but to still go through the
process of checking for and reporting errors.  This it seems to do.

So I was hoping to be able to check (safely) for errors by running fsck -n,
even though the file system was mounted.  Doing so showed errors, so
I ran fsck again with the file system unmounted, and (to my surprise) it
showed no errors.

Hence my original question:  Are the errors that fsck -n showed on my
mounted file system false positives -- not really errors, but rather just
artifacts of the file system being mounted?  Or are they a problem I
should be worrying about (even though they don't show up when the
system is not mounted)?

Thanks for your suggestions and advice.


K. Frank