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



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 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/
> 
> *** Software bugs are stupid.
>     Nevertheless it needs not so stupid people to solve them ***
> 
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> 
> Heinz Mauelshagen                                 Sistina Software Inc.
> Senior Consultant/Developer                       Am Sonnenhang 11
>                                                   56242 Marienrachdorf
>                                                   Germany
> Mauelshagen Sistina com                           +49 2626 141200
>                                                        FAX 924446
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> 
> _______________________________________________
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> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
> 




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