On Sat, Sep 07, 2013 at 09:53:28PM +0300, Alexander Kapshuk wrote:
> <SNIP>
> Based on the 'dmesg' output below, EXT2-fs attempted to mount the '/'
> partition instead of the '/boot' one.
>
> box0 ~ # dmesg|grep 'EXT.*fs'
> [    2.444214] EXT2-fs (sda3): error: couldn't mount because of
> unsupported optional features (240)
> [    2.444736] EXT4-fs (sda3): couldn't mount as ext3 due to feature
> incompatibilities
> [    2.481412] EXT4-fs (sda3): mounted filesystem with ordered data
> mode. Opts: (null)
> [    9.448819] EXT4-fs (sda3): re-mounted. Opts: (null)
> [    9.731383] EXT4-fs (sda5): mounted filesystem with ordered data
> mode. Opts: (null)
>
> Would that suggest a corrupted /boot/grub/grub.conf file?
>
> How did the system boot then?

Most likely your /boot partition is not ext2 as stated in fstab and it
therefore fails to mount (the unsupported optional features hint in that
direction).
Simply try to mount it by hand (mount /boot). If that fails try to mount it
with option -t <filesystem> (for filesystem try ext3 or ext4).

Your system still boots because grub is able to read the filesystem (which
makes corruption unlikely). grub doesn't use fstab or the drivers in the
kernelimage (which isn't even loaded at that point of time).

WKR
Hinnerk