Arch Linux

ArcSnap

Member

Registered: 2025-05-07

Posts: 4

Question about regarding Snapper article in arch wiki.

Question about Snapper page on Arch Linux wiki: https://wiki.archlinux.org/title/Snappe … e_snapshot

Under chapter Restore using the default layout it starts with commands:

# mount -t btrfs -o subvol=/ /dev/disk/by-uuid/UUID_of_root_volume /mnt
# cd /mnt

Do I understand correctly that this is written with assumption entire system is BTRFS and subvol=/  references the / of system?

Can and should this chapter from Arch wiki be applied if OS itself is not BTRFS and only data is on BTRFS?

And what would be steps in case when / is normal EXT4 and /home is a separate hard drive with BTRFS?

Should I still for example do this mv command?

# mv /home /home-backup

Or what would be the exact process when OS itself is not on BTRFS?

Lone_Wolf

Administrator

From: Netherlands, Europe

Registered: 2005-10-04

Posts: 14,971

Re: Question about regarding Snapper article in arch wiki.

Snapper is in archlinux repos, Moving to Newbie Corner

---

Disliking systemd intensely, but not satisfied with alternatives so focusing on taming systemd.

clean chroot building not flexible enough ?
Try clean chroot manager by graysky

V1del

Forum Moderator

Registered: 2012-10-16

Posts: 25,156

Re: Question about regarding Snapper article in arch wiki.

subvol=/ means the root of the btrfs volume and is not strictly related to "the system root". (Every distinct filesystem/partition has their own "root" that's what you invoke with subvol=/ NOT whatever is mounted on /)

you should still be doing this move command, but note that it's

mv @home @home-backup

and is done following a cd into /mnt (long story short, you can follow this exactly as is mentioned there. just replace UUID_of_root_volume with the UUID of your relevant volume)

ArcSnap

Member

Registered: 2025-05-07

Posts: 4

Re: Question about regarding Snapper article in arch wiki.

How should it exactly work?

If I have just this in my fstab

UUID=9c76582a-95c4-437c-abf2-81e3542665ae /home btrfs defaults 0 0

Should I start by creating subvolume first?

Right now if I type:

btrfs subvolume list /home

Then it shows nothing.

However when I initialize snapper:

# btrfs subvolume list /home
# snapper -c homeConf create-config /home
# snapper list-configs
Config   | Subvolume
---------+----------
homeConf | /home 

It works just fine and I can take even snapshots:

# echo "before" > /home/user/test.txt
# snapper -c homeConf create
# echo "after" > /home/user/test.txt

And I can even confirm that snapshots appear:

# ls -a /home
.  ..  .snapshots  user
# cat /home/user/test.txt 
after snapshot
# cat /home/.snapshots/1/snapshot/user/test.txt 
before snapshot

But I cannot do mv:

# mv /home /home-backup
mv: cannot move '/home' to '/home-backup': Device or resource busy

Question: Should I have created some subvolume first? Like this?

btrfs subvolume create /home/@home

My confusion comes from the fact that according to my understanding (not sure if it's correct) snapper already creates some subvolume. And since Snapper already created something I didn't recreate it myself. But from the fact that I am stuck with mv command shows that I should always create subvoume myself and not use what snapper does?

V1del

Forum Moderator

Registered: 2012-10-16

Posts: 25,156

Re: Question about regarding Snapper article in arch wiki.

What subvolume is currently being mounted? If you unmount home and mount it as described you should see multiple @ prefixed "directories" which are your subvolumes. FWIW to check what snapper did you could probably use a btrfs list subvolumes or so https://wiki.archlinux.org/title/Btrfs# … subvolumes

ArcSnap

Member

Registered: 2025-05-07

Posts: 4

Re: Question about regarding Snapper article in arch wiki.

It turned out that I had to manually create a subvolume before creating Snapper configuration. At first I understood that Snapper itself will create a subvolumes. Solution was to create @home subvolume with command

btrfs subvolume create /home/@home

And then fix my fstab to to use subvol=@home parameter to make /home/@home/user-name/ become /home/user-name/

UUID=9c76582a-95c4-437c-abf2-81e3542665ae /home btrfs defaults,subvol=@home 0 0

After that I was able to follow Arch Wiki: https://wiki.archlinux.org/title/Snappe … e_snapshot

Last edited by ArcSnap (2025-05-10 13:38:22)