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Re: [linux-lvm] lvm on loopback mount problems



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 klmontg tmp]# dd if=/dev/zero of=fake_disk.img bs=1M count=500
> 500+0 records in
> 500+0 records out
> [root klmontg tmp]# losetup /dev/loop0 fake_disk.img
> [root klmontg tmp]# pvcreate /dev/loop0
> pvcreate -- physical volume "/dev/loop0" successfully created
> 
> [root 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 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 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 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 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 klmontg tmp]# mount /dev/vgtest/lv_one /mnt
> mount: you must specify the filesystem type
> [root 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 sistina com
> http://lists.sistina.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

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