From: Niall O Broin (niall at domain magicgoeshere.com)
Date: Thu 28 Jun 2001 - 13:57:07 IST
Sorry to bug people, but this is
a) weird enough that I though people might find interesting
b) something to which I need to find an answer
The system is back up now, thus making customer happy, but it's up in a
peculiar manner. The box has a 2G IDE disk which is its boot drive and a 50G
RAID-5 SCSI array. As a standby, I keep a copy of / on a small partition on
the RAID array and this is what has saved the day, but in a very strange
manner. When copying / to the standby, you need to modify /etc/fstab (on the
SCSI disk) so that it's mounted on /dev/sda1 rather than /dev/hda1. Last
time I copied I didn't do that. I have an entry in lilo.conf which says
root=/dev/sda1 although that's for an old kernel . However, I booted using
it and up came the system, with me thinking that it was using /dev/sda1 as /
but because I didn't change the fstab file, it's not. So the solution to get
the box working is to do the following at the LILO prompt:
server root=/dev/sda1
where server is the name of an entry in lilo.conf which points to the
correct kernel but has /dev/hda1 as root. This reads the kernel from the IDE
disk, the kernel starts and loads the init binary from the SCSI disk (I'm
sure of this, because an ls -lut on /sbin/init shows it was last read 33
minutes ago, but the box is only up 16 minutes), init reads /etc/fstab and
when it remounts / rw it's /dev/hda1 it remounts. I thought that perhaps
something in /boot on the IDE disk had been corrupted so I copied /boot from
the SCSI disk to the IDE while booted on the BBC but the box still wouldn't
boot from the IDE disk. At this stage I'm fscking baffled. I did earlier do
an md5sum on both the init binaries and they're identical although I didn't
check the libraries that init uses - that's next, but it requires another
boot to the BBC (because in this strange boot from /dev/sda1 but then use
/dev/hda1 as / scenario, I can't mount /dev/sda1 anywhere else - I get told
that it's busy, although it's not mounted and there's no entry for it in
/etc/mtab.)
So, that's the tale up to date. Guesses still welcome :-)
Niall
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