[Bug 246324] Re: initramfs-tools lvm2-hookscript won't include lvm.conf and claim devices it shouldn't

Maxim Doucet maxim at alamaison.fr
Tue Jan 6 17:37:39 UTC 2009


I also encounter this problem in the same configuration: LVM on top of
DRBD.

Here's the setup:
 * a DRBD device is created from a standard partition (ie. /dev/sda6). The drbd device is named /dev/drbd0
 * /dev/drbd0 is a LVM's PV (Physical Volume): pvcreate /dev/drbd0
 * this DRBD's Physical Volume contains a LVM Volume Group (VG) which itself contains several LVM Logical Volumes (ie. /dev/mapper/vgstor-lv1)

Because /dev/drbd0 is a device based on /dev/sda6, we have to make sure
that LVM does not use /dev/sda6 when it gets initalized. In other words,
/dev/drbd0 must be the device to use for LVM's initialization. This is
done thanks to a filter in /etc/lvm/lvm.conf which rejects all devices
but DRBD ones. Here's the LVM rule inside /etc/lvm/lvm.conf:

    filter = [ "a|/dev/drbd.*|", "r|.*|" ]

Now indeed everything works fine... until the next boot.

Here's the problem on next boot: as described in the bug, the initramfs-
tools hookscript doesn't include for /etc/lvm/lvm.conf. The consequence
is that all devices are scanned for LVM tags, in order to create Logical
Volumes devices in /dev/mapper/.

In my exemple, because /dev/sda6 is not filtered during initramfs's
boot, the Logical Volume /dev/mapper/vgstor-lv1 is created. Now,
/etc/init.d/drbd is launched later in the boot sequence. It tries to use
/dev/sda6 to create /dev/drbd0 but it fails saying:

     /dev/drbd0: Failure: (114) Lower device is already claimed. This
usually means it is mounted.

A dirty workaround is to delete the LVM device with:
    dmsetup remove /dev/mapper/vgstor-lv1

... then to launch DRBD.

The good fix is of course to take care to include /etc/lvm/lvm.conf with
the initramfs-tools hookscript just as described in the bug.

Problem encountered on a default Ubuntu 8.10 Server edition.

-- 
initramfs-tools lvm2-hookscript won't include lvm.conf and claim devices it shouldn't 
https://bugs.launchpad.net/bugs/246324
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