How to properly use the subvolume and snapshot for a backup method

Hi everyone, first of all, I want to say that I'm learning how to use BTRFS and I really enjoy all the subvolume and the snapshot features.

Also, I'm a backup freak :P

Basically, I have 4 questions :

1. I would like to know what is the best way to install a Linux distribution inside a BTRFS partition ? I mean, do I install it directly inside the subvolid=0 or I create a subvolume for exemple @root to leave the subvolid=0 clean and without any data, of course only subvolume and then I install my distro inside the @root subvolume ? I'm asking that, because I saw that Ubuntu 11.04 use the subvolume @ and @home to install the distribution files so, the subvolid=0 is clean.
I saw that because at boot time, the /boot/grub/grub.cfg use this param with Grub2 : rootflags=subvol=@

2. I would like to know if this Live backup method is correct ?

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My /dev/sda2 contains a @root subvolume that contains my distribution, my /home directory is inside an another subvolume that is at the same level that @root.

# mkdir /mnt/disklayout
# mount /dev/sda2 /mnt/disklayout -o subvolid=0

# cd /mnt/disklayout
# btrfs subvolume snapshot @root snapshot-@racine-live
# btrfs subvolume snapshot @home snapshot-@home-live

# mount /dev/sdb1 /mnt/backup -o subvol=@backup

# time rsync -aHA --del --force --stats --progress
snapshot-@racine-live/ /mnt/backup/funtoo
# time rsync -aHA --del --force --stats --progress snapshot-@home-live/
/mnt/backup/funtoo/home
# time rsync -aHA --del --force --stats --progress /boot/
/mnt/backup/funtoo/boot

# cd /mnt/disklayout
# btrfs subvolume delete snapshot-@root-live
# btrfs subvolume delete snapshot-@home-live

# cd /
# umount /mnt/disklayout

Creation of the snapshot :

# cd /
# umount /mnt/backup
# mount /dev/sdb1 /mnt/backup -o subvolid=0

# cd /mnt/backup
# btrfs subvolume snapshot @backup @snap-20110502
# btrfs subvolume list .

# cd /mnt/backup
# ls -la
# cd @snap-20110502
# ls -la
# cd /
# umount /mnt/backup  

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3. Is there any objection to use a snapshot name or a subvolume that start with a @ ?

4. Finally,I would like to know if we can rename subvolume ?

The best example is this : I crash my box but I made earlier a snapshot that is named @snap-20110502 inside my subvolid=0. Now that my @root is brain dead, I would like to delete it and rename the @snap-20110502 to @root ?

Is this possible and if so, can I use the mv command or something else ? I'm sure that I will need to boot with a LiveCD to do so, but for the rest, is this possible ?

Thanks you very much !!!

Salut
alp
Sylvain

I do so

to me it seems correctly

I did without trouble

I tweaked a bit the grub script (under /etc/grub.d/);now when I run "update-grub", the grub.cfg contains also some entries which permit do boot in the snapshot subvolume. Basycally these entries contains the replace the parameter "rootflags=subvol=@" in "rootflags=subvol=<subvolume name>". Is far to be optimal, but doing so I don't need any LiveCD.

For example in a snapshot I am testing systemd ...