[linux-lvm] mount root filesystem on lvm

Manfred Gschweidl m.gschweidl at inode.at
Mon May 12 17:38:02 UTC 2003

thanks for your help.

after more than one week, now my system boots cleanly without problems, 
and everything is ok now.

greetings from austria,


Christophe Saout wrote:
> Am Son, 2003-05-11 um 21.38 schrieb Manfred Gschweidl:
>>uupps...sorry, maybe i should carefully read my mails, after writing 
>>them. ;-)
>>i mean only one entry exists in "/dev/mapper", and this is "control", 
>>but no other entry.
> Ah, ok, I'm seeing. Well, I think that's a problem with LVM2. At the
> moment the device files are created either when a volume group gets
> activated or when it is already active and you add a logical volume.
> But when the volume group got activated by the ramdisk and the system
> switches the root filesystem, you now don't have the devices files.
> I think that's where "lvm mknodes" should kick it, but... not
> implemented yet. And you can't deactivate and reactivate the volume
> group because the root filesystem on it is mounted.
> Great. :D
> So it looks like you must create the device files manually.
> cd /dev/mapper
> mknod volumegroupname-logicalvolumename b 254 0
> mknod volumegroupname-logicalvolumename b 254 1
> ...
> After that you also should create the symlinks
> cd /dev/volumegroupname
> ln -s ../mapper/volumegroupname-logicalvolumename logicalvolumename
> ...
> Since you already put an ls command into the ramdisk before you should
> know which minor got assigned to which volume.
> Or, perhaps this should work: AFAIK if you have a directory /initrd on
> your root filesystem, the old ramdisk should be moved there after the
> root filesystem is mounted, so you can just copy the directories and
> device files that got create there in /dev (/initrd/dev/mapper and
> /initrd/dev/volumegroupname) to your /dev. But I have never tested this.
> This sounds rather ugly and complicated, but it only occurs when
> switching from LVM1 to LVM2 while having it mounted (because you can't
> activate it via LVM2 while running on the real filesystem where the
> device nodes should be created correctly. Or wait until the mknodes
> command is finished or implement it yourself. ;-)

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