[linux-lvm] lvm on loopback mount problems
Paulson McIntyre
gpmidi at k4lrg.org
Sun Oct 19 11:36:01 UTC 2003
I tryed the same procedure on my rh9 box; dident work for me either. I
then used dd to create a random file the same size as the lv i had
created, copyed the data onto the lv, copyed the data off the lv, and
did a 'cmp'...they differ at byte1, line1.
On Wed, 2003-09-24 at 04:33, Heinz J . Mauelshagen wrote:
> Never seen this here.
> Did a quick test and it works with 1.0.7 on 2.4.21 vanilla here.
> It could be a problem with that RedHat kernel.
>
> Regards,
> Heinz -- The LVM Guy --
>
>
> On Tue, Sep 23, 2003 at 05:14:31PM -0400, Montgomery, Kendal L wrote:
> > I've seen a few things about using lvm on a loopback filesystem, but nothing
> > concrete, so I tried it myself. Most everything works okay until I get to
> > acutally mounting the filesystem. Here are the steps I did:
> >
> > [root at klmontg tmp]# dd if=/dev/zero of=fake_disk.img bs=1M count=500
> > 500+0 records in
> > 500+0 records out
> > [root at klmontg tmp]# losetup /dev/loop0 fake_disk.img
> > [root at klmontg tmp]# pvcreate /dev/loop0
> > pvcreate -- physical volume "/dev/loop0" successfully created
> >
> > [root at klmontg tmp]# vgcreate /dev/vgtest /dev/loop0
> > vgcreate -- INFO: using default physical extent size 4 MB
> > vgcreate -- INFO: maximum logical volume size is 255.99 Gigabyte
> > vgcreate -- doing automatic backup of volume group "vgtest"
> > vgcreate -- volume group "vgtest" successfully created and activated
> >
> > [root at klmontg tmp]# lvcreate --name lv_one --size 200M /dev/vgtest
> > lvcreate -- doing automatic backup of "vgtest"
> > lvcreate -- logical volume "/dev/vgtest/lv_one" successfully created
> >
> > [root at klmontg tmp]# mke2fs /dev/vgtest/lv_one
> > mke2fs 1.32 (09-Nov-2002)
> > Filesystem label=
> > OS type: Linux
> > Block size=1024 (log=0)
> > Fragment size=1024 (log=0)
> > 51200 inodes, 204800 blocks
> > 10240 blocks (5.00%) reserved for the super user
> > First data block=1
> > 25 block groups
> > 8192 blocks per group, 8192 fragments per group
> > 2048 inodes per group
> > Superblock backups stored on blocks:
> > 8193, 24577, 40961, 57345, 73729
> >
> > Writing inode tables: done
> > Writing superblocks and filesystem accounting information: done
> >
> > This filesystem will be automatically checked every 26 mounts or
> > 180 days, whichever comes first. Use tune2fs -c or -i to override.
> > [root at klmontg tmp]# e2fsck /dev/vgtest/lv_one
> > e2fsck 1.32 (09-Nov-2002)
> > Couldn't find ext2 superblock, trying backup blocks...
> > e2fsck: Bad magic number in super-block while trying to open
> > /dev/vgtest/lv_one
> >
> > The superblock could not be read or does not describe a correct ext2
> > filesystem. If the device is valid and it really contains an ext2
> > filesystem (and not swap or ufs or something else), then the superblock
> > is corrupt, and you might try running e2fsck with an alternate superblock:
> > e2fsck -b 8193 <device>
> >
> > [root at klmontg tmp]# e2fsck -b 8193 /dev/vgtest/lv_one
> > e2fsck 1.32 (09-Nov-2002)
> > e2fsck: Bad magic number in super-block while trying to open
> > /dev/vgtest/lv_one
> >
> > The superblock could not be read or does not describe a correct ext2
> > filesystem. If the device is valid and it really contains an ext2
> > filesystem (and not swap or ufs or something else), then the superblock
> > is corrupt, and you might try running e2fsck with an alternate superblock:
> > e2fsck -b 8193 <device>
> >
> > [root at klmontg tmp]# mount /dev/vgtest/lv_one /mnt
> > mount: you must specify the filesystem type
> > [root at klmontg tmp]# mount -t ext2 /dev/vgtest/lv_one /mnt
> > mount: wrong fs type, bad option, bad superblock on /dev/vgtest/lv_one,
> > or too many mounted file systems
> >
> > As you can see, one the filesystem was made, nothing else works. I can't
> > fsck the filesystem on the new logical volume, or mount it. This is
> > obviously a problem since, well, it's useless unless I can mount it.
> >
> > I'm using RedHat 9 with the 2.4.20-20.9 kernel. I've also tried this on
> > RedHat 8 on another box. I got the latest version of util-linux which is
> > 2.11z and compiled that (in case it was a possible bug in mount 2.11y which
> > comes with redhat). I'm using lvm 1.0.3-12 that comes with redhat 9. I
> > have not tried getting the latest lvm tools. That's my next step...
> >
> > Anyone else had this problem, or tried doing this? The reason I wanted to
> > do this in the first place is so I can test snapshots. I want to be able to
> > have a filesystem which is static, that I will then take a snapshot of, then
> > change things on it, and then use the snapshot to bring it back to it's
> > original form. I know there is some work on union filesystems or
> > translucent filesystems, and such things, but none of it seems mature
> > enough, so this solution seemed like it might work until I hit this snag.
> >
> > Is anyone else doing this (lvm on loopback)? Does anyone have it working
> > correctly? Am I doing something wrong? Do I need a different version of
> > something?
> >
> > Thanks in advance for any help.
> >
> > Kendal.
> >
> > _______________________________________________
> > linux-lvm mailing list
> > linux-lvm at sistina.com
> > http://lists.sistina.com/mailman/listinfo/linux-lvm
> > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>
> *** Software bugs are stupid.
> Nevertheless it needs not so stupid people to solve them ***
>
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>
> Heinz Mauelshagen Sistina Software Inc.
> Senior Consultant/Developer Am Sonnenhang 11
> 56242 Marienrachdorf
> Germany
> Mauelshagen at Sistina.com +49 2626 141200
> FAX 924446
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>
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