<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> <HTML> <HEAD> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=US-ASCII"> <META NAME="Generator" CONTENT="MS Exchange Server version 5.5.2653.12"> <TITLE>lvm on loopback mount problems</TITLE> </HEAD> <BODY> 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. </BODY> </HTML>