Re: [gentoo-user] running e2fsck pre-mount

[Willie Wong]

On Tue, Sep 08, 2009 at 08:37:49PM -0600, Penguin Lover Maxim Wexler squawked:
> On an Asus netbook during boot after the line
>
> *checking all filesystems
>
> there'll be a message something like 'filesystem mounted 36 times
> without being checked. Check forced' then something like '17.1%
> non-contiguous' then a long delay. Then one of two things, either a
> message saying 'errors fixed' or a forced reboot.

A feature of mount and a feature of e2fs. First, from man 5 fstab

The  sixth field, (fs_passno), is used by the fsck(8) program to deter-
mine the order in which filesystem checks are done at reboot time.  The
root  filesystem  should  be specified with a fs_passno of 1, and other
filesystems should have a fs_passno of 2.  Filesystems within  a  drive
will  be checked sequentially, but filesystems on different drives will
be checked at the same time to utilize  parallelism  available  in  the
hardware.   If  the sixth field is not present or zero, a value of zero
is returned and fsck will assume that the filesystem does not  need  to
be checked.

Now you know what the last dangling number in /etc/fstab is for! For
most of my partitions, except the root one, I set it to 0. Mostly
because that my partitions are in ReiserFS. 

However, it is probably set to 0 in your case, otherwise the message
you saw wouldn't have happened. 

Next, if you look at man tune2fs, you'd see the option '-c', which
(just quoting the relevant parts)

Adjust the number of mounts after which the filesystem will be checked
by e2fsck. If [the number] is 0 or -1, the number of times the
filesystem is mounted will be disregarded by e2fsck. 

>
> What does it mean 'without being checked' Does the boot process expect
> a filesystem check, in this case e2fsck? Why should their be errors. I
> shut the machine like this '#shutdown -h(or -r) now' Everything is
> unmounted and the machine turns off without a glitch that I''m aware
> of.

More from the manpage for tune2fs:

You should strongly consider the consequences of disabling
mount-count-dependent checking entirely. Bad disk drives, cables,
memory, and kernel bugs could all corrupt a filesystem without
makrking the filesystem dirty or in error. If you are using journaling
on your filesystem, your filesystem will never be marked dirty, so it
will not normally be checked. A filesystem error detected by the
kernel will still force an fsck on the next reboot, but it may already
be too late to prevent data loss at that point. 

Basically, since you don't ask the filesystems to be checked on every
boot, to make sure your fs's are sane, ext2/3 will ask the filesystems
to be checked every X mounts (also every T period of time, see the -i
option in tune2fs for details). Like the manpage said, sh*t happens,
and it is better that you check once in a while. 

However, if every single time when the fsck is run you either reboot
or there is an error... there maybe something wrong with your
hardware. If you don't have smartd installed, you should consider it,
your data on the harddrive should be worth your time. 


W
-- 
There was a man in a nuthouse who constantly scared off all the newcomers with 
a menacing smile and the dreadful-sounding phrase, "I differentiate you! I 
differentiate you!"--invariably the newcomer would cower in the corner and stay
far away from the man. However, one day another man came in and confronted the 
first man. Of course, the first began yelling at the newcomer, "I differentiate
you! I differentiate you!" But it had no effect on the newcomer. The man yelled
"I differentiate you!" several times to no avail. Finally, he broke down in 
tears. "Why, why?!?" he asked.

The second man stated simply, "I'm e^x."
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