[RndTbl] boot / fsck debug shells
trevor at tecnopolis.ca
Wed Dec 14 02:34:41 CST 2011
Further to Gilbert's debug shell keyboard issues:
I've been dealing with lots of md upgrade problems lately and non-boot
scenarios. Not sure if you're seeing the same thing, but what's worked
great for me is boot with kernel args: rdshell rddebug. Don't use the
sushell or whatever it was you were mentioning as that forces your login.
When the system can't boot due to md / fsck it will drop you in a rdshell
(real crap shell) without any pw prompt. From there you can run mdadm
commands, and probably fsck, to get your system bootable. In fact, once
you get your / fs alive you can mount it to /sysroot and type "exit" and
the system will boot as normal!
Once in the live system you can run "dracut" (possibly with --force) to
create a fixed/bootable rd. Assuming that's your problem.
I've used this TONS lately when upgrading linux boxes from non-raid to md
raid or small disks (raid) to bigger disks (raid). Any situation where
your drive labels/uuids/majors/minors change can fark up your booting.
This lets you fix it (without OS reinstall).
Had a horrible time just this last week where I had booting md complain
that sda3 and sda shared a md superblock and it wouldn't boot. Even with
the above tools, I couldn't get it to boot without manual rdshell
intervention until I revamped the whole disk so that there was a tiny bit
of space at the very end of the disk, so sda had its own tiny area at the
end (and I zeroed its superblock).
Anyhow, just thought perhaps there may be some overlap in problems and I
could save you some headache.
Linux: the (nearly) only OS you can always fix and never need to reinstall
(upgrade or wipe/install). Love it!
(Note to others, this stuff may be RH/Fedora specific as I have no idea if
other distros use dracut or provide rdshell.)
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