3 Create An LVM Snapshot Of /

Now it's time to create the snapshot of the /dev/server1/root volume. We will call the snapshot rootsnapshot:

lvcreate -L10G -s -n rootsnapshot /dev/server1/root

The output of

lvdisplay

should look like this:

server1:~# lvdisplay
  --- Logical volume ---
  LV Name                /dev/server1/root
  VG Name                server1
  LV UUID                UK1rjH-LS3l-f7aO-240S-EwGw-0Uws-5ldhlW
  LV Write Access        read/write
  LV snapshot status     source of
                         /dev/server1/rootsnapshot [active]
  LV Status              available
  # open                 1
  LV Size                9.30 GB
  Current LE             2382
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           254:0

  --- Logical volume ---
  LV Name                /dev/server1/swap_1
  VG Name                server1
  LV UUID                2PASi6-fQV4-I8sJ-J0yq-Y9lH-SJ32-F9jHaj
  LV Write Access        read/write
  LV Status              available
  # open                 2
  LV Size                464.00 MB
  Current LE             116
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           254:1

  --- Logical volume ---
  LV Name                /dev/server1/backups
  VG Name                server1
  LV UUID                sXq2Xe-y2CE-Ycko-rCoE-M5kl-E1vH-KQRoP6
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                30.00 GB
  Current LE             7680
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           254:2

  --- Logical volume ---
  LV Name                /dev/server1/rootsnapshot
  VG Name                server1
  LV UUID                9zR5X5-OhM5-xUI0-OolP-vLjG-pexO-nk36oz
  LV Write Access        read/write
  LV snapshot status     active destination for /dev/server1/root
  LV Status              available
  # open                 1
  LV Size                9.30 GB
  Current LE             2382
  COW-table size         10.00 GB
  COW-table LE           2560
  Allocated to snapshot  0.01%
  Snapshot chunk size    8.00 KB
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           254:5

We want to mount /dev/server1/rootsnapshot on /mnt/server1/rootsnapshot, so we have to create that directory first:

mkdir -p /mnt/server1/rootsnapshot

Then we mount our snapshot:

mount /dev/server1/rootsnapshot /mnt/server1/rootsnapshot

Then we run

ls -l /mnt/server1/rootsnapshot/

This should show all directories and files that we know from our / partition:

server1:~# ls -l /mnt/server1/rootsnapshot/
total 132
drwxr-xr-x  2 root root  4096 2007-04-10 21:02 backups
drwxr-xr-x  2 root root  4096 2007-04-10 20:35 bin
drwxr-xr-x  2 root root  4096 2007-04-10 20:25 boot
lrwxrwxrwx  1 root root    11 2007-04-10 20:25 cdrom -> media/cdrom
drwxr-xr-x 13 root root 40960 2007-04-10 20:36 dev
drwxr-xr-x 57 root root  4096 2007-04-10 21:09 etc
drwxr-xr-x  3 root root  4096 2007-04-10 20:36 home
drwxr-xr-x  2 root root  4096 2007-04-10 20:26 initrd
lrwxrwxrwx  1 root root    28 2007-04-10 20:29 initrd.img -> boot/initrd.img-2.6.18-4-486
drwxr-xr-x 13 root root  4096 2007-04-10 20:34 lib
drwx------  2 root root 16384 2007-04-10 20:25 lost+found
drwxr-xr-x  4 root root  4096 2007-04-10 20:25 media
drwxr-xr-x  2 root root  4096 2006-10-28 16:06 mnt
drwxr-xr-x  2 root root  4096 2007-04-10 20:26 opt
drwxr-xr-x  2 root root  4096 2006-10-28 16:06 proc
drwxr-xr-x  3 root root  4096 2007-04-10 20:42 root
drwxr-xr-x  2 root root  4096 2007-04-10 20:36 sbin
drwxr-xr-x  2 root root  4096 2007-03-07 23:56 selinux
drwxr-xr-x  2 root root  4096 2007-04-10 20:26 srv
drwxr-xr-x  2 root root  4096 2007-01-30 23:27 sys
drwxrwxrwt  2 root root  4096 2007-04-10 21:09 tmp
drwxr-xr-x 10 root root  4096 2007-04-10 20:26 usr
drwxr-xr-x 13 root root  4096 2007-04-10 20:26 var
lrwxrwxrwx  1 root root    25 2007-04-10 20:29 vmlinuz -> boot/vmlinuz-2.6.18-4-486

So our snapshot has successfullly been created!

Now we can create a backup of the snapshot on the /backups partition using our preferred backup solution. For example, if you like to do a file-based backup, you can do it like this:

tar -pczf /backups/root.tar.gz /mnt/server1/rootsnapshot

And if you like to do a bitwise backup (i.e. an image), you can do it like this:

dd if=/dev/server1/rootsnapshot of=/backups/root.dd

server1:~# dd if=/dev/server1/rootsnapshot of=/backups/root.dd
19513344+0 records in
19513344+0 records out
9990832128 bytes (10 GB) copied, 320.059 seconds, 31.2 MB/s

You could also use both ways to be prepared for whatever might happen to your /dev/server1/root volume. In this case, you should have two backups afterwards:

ls -l /backups/

server1:~# ls -l /backups/
total 9947076
drwx------ 2 root root      16384 2007-04-10 21:04 lost+found
-rw-r--r-- 1 root root 9990832128 2007-04-10 21:28 root.dd
-rw-r--r-- 1 root root  184994590 2007-04-10 21:18 root.tar.gz

Afterwards, we unmount and remove the snapshot to prevent it from consuming system resources:

umount /mnt/server1/rootsnapshot
lvremove /dev/server1/rootsnapshot

That's it, you've just made your first backup from an LVM snapshot.