[sclug] Fsck after an unexpected shutdown

[Sapan Ganguly]

Excellent, thanks guys.  There shouldn't be a problem with setting it to do
an fsck after every unexpected shutdown instead of only if I'm there to
press 'Y'.

On 4/6/06, Alex Butcher <lug at assursys.co.uk> wrote:
>
> On Thu, 6 Apr 2006, Sapan Ganguly wrote:
>
> > I have an ext3 filesystem, if my machine is powered off unexpectedly the
> > next time it boots up it asks me if I want to do an fsck, shouldn't
> > journalling negate the need for this?
>
> Usually, yes.
>
> > I read somewhere that if you do hit 'Y' for an fsck and you have a
> > journalled filesystem you may risk screwing things up.
>
> This is what <http://www.brunolinux.com/04-The_File_System/Auto_Fsck.html>
> says:
>
> "In case of a hard-reset, init messages indicate the computer was not shut
> down cleanly, and a message appear :"Press Y within 5 seconds to force the
> file system check "Actually this is very misleading : if you do it with
> ext3, it does NOT use the journal and then you will experience system
> losses. Lots of newbies have reported that problem. Now that would be nice
> to change this message so that people leave the journalisation do the good
> work. --Eric"
>
> This came as a surprise to me, as I try to remember to hit the Y key when
> I
> know I've shut a machine down uncleanly, hoping to force the most paranoid
> checking. I've never (knowingly) lost any data, and I'm quite particular.
>
> > Is that true?
>
> Looking at e2fsck(8), we have:
>
> "E2fsck also supports ext2 filesystems containing a journal, which are
> also  sometimes known as ext3 filesystems, by first applying the jour-
> nal to the filesystem before continuing with normal e2fsck processing."
>
> This appears to mean that e2fsck_run_ext3_journal() is called.
>
> and
>
> "After  the  journal  has  been  applied, a filesystem will normally be
> marked as clean."
>
> Reading rc.sysinit, hitting the 'Y' key appends '-f' to fsck's options.
> According to the fsck manpage, -f:
>
> "-f     Force checking even if the file system seems clean."
>
> Looking at the source for e2fsprogs-1.38 as supplied with FC3, this sets
> the
> E2F_OPT_FORCE bit in the internal options flag, which appears to force a
> check, via check_if_skip() called from unix.c/main() AFTER the calls to
> e2fsck_check_ext3_journal and e2fsck_run_ext3_journal() from unix.c
> /main().
> The only reasons the journal recovery gets skipped is if a) fsck is doing
> a
> read-only check, or b) if it detects the journal has been run twice (due
> to
> bogus hardware or device driver)
>
> Therefore, I'm of the opinion that Eric's comment on the brunolinux.com
> article is incorrect, and has always been incorrect. From the Changelog:
>
> "2001-12-21  Theodore Tso  <tytso at mit.edu>
>
> [...]
>          * e2fsck.h (E2F_OPT_FORCE), unix.c (PRS, check_if_skip): Use a
>                  bitfield in the e2fsck context flags word to indicate
>                  whether or not a check should be forced.  This allows the
>                  journal code to set the option if necessary to force a
>                  filesystem check."
>
> Sure enough, e2fsck_check_ext3_journal can set E2F_OPT_FORCE, just like
> the
> -f switch.
>
> > Thanks,
> > Sapan
>
> HTH,
> Alex.
> --
> Alex Butcher      Brainbench MVP for Internet Security: www.brainbench.com
> Bristol, UK                      Need reliable and secure network systems?
> PGP/GnuPG ID:0x5010dbff                         <http://www.assursys.com/>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.tmdg.co.uk/pipermail/sclug/attachments/20060406/267060dd/attachment.htm