Re: / on LVM and rescue

After a long battle with technology, der.hans wrote:
> RedHat defaults to putting root on an LVM. It generally boots and works
> fine. For the times where it doesn't boot correctly, I'm trying to learn how
> to rescue the system.
>
> I'm trying to use System Rescue CD to boot the currently installed system.
> It's not working. Grub lists root as /dev/VolGroup00/LogVol00, but
> specifying that ( and several other variations ) doesn't work.

/boot *CANNOT* be on LVM. The x86 BIOS is just too simple to grok LVM, so
your /boot, kernel image, initrd, stage 1.5, stage2, and so forth must be on
a regular partition. If you don't have a /boot , then your / needs to be on
a regular partition. The root= bit in the "kernel" can of course refer to an
LV if you have device-mapper and all that junk compiled into the kernel or in
the initrd.

> What's the magic goo needed to get grub to boot and use a root partition
> on LVM?

If your / is on an LV, you typically need to have GRUB load an initrd that
contains the LVM tools as well as other junk. One should be provided with
Redhat in /boot . Something sort of like:

title CentOS (2.6.18-53.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-53.el5 ro root=/dev/vg00/lv00
initrd /initrd-2.6.18-53.el5.img

...that's from CentOS, but that's similar to Redhat. I dunno, I kept my / on
a regular partition just because so many things don't understand LVM that
well. (/usr, /home, /var, /data ... all on LVs!) HTH,

--
You have me mixed up with more creative ways of being stupid.
--MegaHAL, trained on random gibberish
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Matt G|There is no Darkness in Eternity/But only Light too dim for us to see
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