ZZZZOn Thu, 1 May 2008, Charles Marcus wrote:
> In Gerry's scenario here, if the snapshot volume had NOT been on a ram
> disk, would he have had the problem he had or not?
Here is the snip from Fedora/RHEL for activating the VG containing
the root filesystem (note: kernel modules and lvm command are contained in
initrd filesystem, and do not depend on /lib/modules/...):
...
echo "Loading dm-mod.ko module"
insmod /lib/dm-mod.ko
echo "Loading dm-mirror.ko module"
insmod /lib/dm-mirror.ko
echo "Loading dm-zero.ko module"
insmod /lib/dm-zero.ko
echo "Loading dm-snapshot.ko module"
insmod /lib/dm-snapshot.ko
echo Making device-mapper control node
mkdmnod
mkblkdevs
echo Scanning logical volumes
lvm vgscan --ignorelockingfailure
echo Activating logical volumes
lvm vgchange -ay --ignorelockingfailure rootvg
...
This will fail if any of the physical volumes are missing. More logic
in initrd is required to boot with missing PVs.
So yes, a ram disk is guaranteed to be missing on reboot, and thus to
fail in the RH/Fedora distros. There is no problem taking snapshots
of the root fs otherwise. If there is a robust way to reduce
missing PVs automagically in the above script from initrd, Fedora could
use the contribution.
--
Stuart D. Gathman <stuart@bmsi.com>
Business Management Systems Inc. Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.
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