Take the 2-minute tour ×
Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

I created a lvm snapshot like so:

lvcreate -L 5G -s -n root-snapshot /dev/VolGroup00/LogVol00

Then I mounted the snapshot like so:

mount /dev/VolGroup00/root-snapshot /mnt/root-snapshot/

Now, when I see what's in the dev tree in the snapshot, almost everything is missing except for two items:

[root@server1 ~]# ls /mnt/root-snapshot/dev
mapper  VolGroup00

And there is nothing inside proc. Why is this? I know proc is a virtual fs, but when the snapshot was taken, the system was running and hence there was a lot of stuff in proc and dev... why are they missing in the snapshot.

I particularly needed:

/dev/console
/dev/initctl
/dev/null
/dev/zero

for my backup.

Edit: mount actually reveals that proc is mounted fs on / But what about dev... mount does not show dev being mounted outside of LVM?

/dev/mapper/VolGroup00-LogVol00 on / type ext3 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/sda1 on /boot type ext3 (rw)
tmpfs on /dev/shm type tmpfs (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)
/dev/mapper/VolGroup00-root--snapshot on /mnt/root-snapshot type ext3 (rw)
share|improve this question

3 Answers 3

up vote 1 down vote accepted

They are not real filesystems, and not part of the root filesystem that you created a snapshot on.

But lets ignore that. I am guessing you are asking about the /proc and /dev mounts because you want to chroot into your snapshot? Or the backup tools run within the snapshot directory? If so, why not simply do a bind-mount in addition to mounting the snapshot.

mount /dev/VolGroup00/root-snapshot /mnt/root-snapshot/
mount -o bind /dev/ /mnt/root-snapshot/dev/
mount -o bind /proc/ /mnt/root-snapshot/proc/

When you are ready to unmount your snapshot simply unmount /mnt/root-snapshot/dev/ and /mnt/root-snapshot/proc/ before unmounting /mnt/root-snapshot/

share|improve this answer
    
awesome... thanks.. this is what I was looking for :) –  Sharad Oct 27 '11 at 21:52

/proc and /dev are both virtual file systems that are not at all kept on the LVM volume (as the output of mount will confirm), therefore they are not included in an LVM snapshot.

Both are generated by the kernel at runtime, and there is no need to back them up to begin with.

share|improve this answer
    
thank. pls see my edit –  Sharad Oct 27 '11 at 21:25

An LVM dump would only contain what is on that specific filesystem NOT on any other mounts. The /proc and perhaps /dev are mounted filesystem under root and the data thus is NOT contained within the LVM.

What you would have to do is to back them up specially with something like tar or cpio.

BTW, I would NEVER backup the /proc filesystem as there is nothing archival in it and you may end up with a huge number of process memory dumps.

share|improve this answer
    
yes, you're right.. proc fs is indeed mounted under root... as revealed by mount. but dev is not. see my mount output in my original question. thanks –  Sharad Oct 27 '11 at 21:24
    
I have SuSE...here is the mount line: devtmpfs on /dev type devtmpfs (rw,mode=0755) –  mdpc Oct 27 '11 at 22:09

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.