e2fsck discrepancies

Roland Bock rbock at eudoxos.de
Fri Oct 24 17:49:57 UTC 2008


thanks for the confirmation. Now that I read again the man page, I 
wonder how I could miss that part:

"[...] How-
ever,  even  if  it  is  safe to do so, the results printed by e2fsck 
are not valid if the
filesystem is mounted."

Blessed is he who can read :-)

Best regards,


Eric Sandeen wrote:
> Roland Bock wrote:
>> Hi,
>> yesterday I ran e2fsck -n on a mounted file system and got:
>> /dev/sdb1 contains a file system with errors, check forced.
>> According to Ted, the lines that followed were not to be trusted due to 
>> the fact that the file system was mounted. But this error statement 
>> suggests to run a check with the fs unmounted.
>> Today, we scheduled a downtime and ran the check. It came of completely 
>> clean:
>> ~: e2fsck -fy /dev/sdb1
>> e2fsck 1.40.8 (13-Mar-2008)
>> Pass 1: Checking inodes, blocks, and sizes
>> Pass 2: Checking directory structure
>> Pass 3: Checking directory connectivity
>> Pass 4: Checking reference counts
>> Pass 5: Checking group summary information
>> /dev/sdb1: 32028520/536870912 files (0.5% non-contiguous), 
>> 802465197/2147460933 blocks
>> Does this mean that read-only checks are generally not trustworthy, even 
>> the statement that the filesystem has errors? Or something like
>> Read-only reports clean: fine
>> Read-only reports error: not necessarily really an error
> I think that's possible.  When e2fsck starts off, main() does:
> main()
> 	check_super_block()
> 		if some sanity tests fail
> 			ext2fs_unmark_valid()
> 	check_if_skip()
> 		if EXT2_ERROR_FS || !ext2fs_test_valid()
> 			" contains a file system with errors"
> check_if_skip is what issues the "contains a file system with errors"
> message, and it may do so if the filesystem is marked with errors, OR if
> a call to ext2fs_test_valid() fails.
> Prior to this, check_super_block() may call ext2fs_unmark_valid() for a
> variety of reasons, some of which could, I think, be caused by the
> filesystem being live and not necessarily consistent when viewed by e2fsck.
> So I think that the message is a bit misleading; "filesystem with
> errors" sounds to me like EXT2_ERROR_FS, which should always issue some
> sort of message to the syslog when set - but, you may also get the
> "filesystem with errors" message due to some inconsistencies that may be
> wholly due to the filesystem being mounted and in flux as fsck tries to
> read it.
> -Eric

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