Can I fsck the HD install from the CD?

OK, first the problem: every so often (usually at a scheduled fsck) the HD install of 3.1 decides to mount /dev/null as read only. (I've no idea why: it seems that something is arbitarily setting the permissions to paranoid).

Sometimes I've been able to get out of this by logging on as root and simply resetting the permissions. This time, I'm doomed: post fsck I get a bash prompt with:

bash: /dev/null is read only

repeated umpteen times. I can't even get a shell or a login -- it won't accept input. It looks like the only way back (I can't fsck from my SuSE as ef2fs is an earlier version) is to somehow do it from the CD. But I get the message:

the filesystem must be mounted read/write (not a great idea when running fsck!) or you must be root.

Ideas, please!

This is what I did (and it worked!) thanks to the Debian and Linux Format lists for the answer!

I got in by using the CD and knoppix 2. Mounting the offending drive and chmodding /dev/null 777 and then rebooting into the HD install had the effect of attempting to fsck the drive and reporting the same /dev/null read only problem, but fscking from knoppix 2 (not mounting, of course!) had the desired effect. On checking permissions, they're read/write for everyone.

Looks like something may be reading the permissions wrong and reporting that to fsck, but I've no further ideas on that one!

Sheesh! I'll re-build the kernel this weekend with a vanilla 2.4.20 and look at maybe putting a different version of fsck on.

Any ideas what might be causing this strange and -- to me -- baffling issue would be very welcome, as wierdness aside, I like what I've got (but the learning curve is pretty steep).