Arch Linux

ilblasco

Member

Registered: 2021-02-22

Posts: 7

Enable snapshots for Luks on LVM system

Hello!

I apologize for the length of the message.

CURRENT STATUS:
- Fresh install (LUKS on LVM, btrfs filesystem, grub bootloader)
- No subvolumes (at least not created on purpose)
- /etc/fstab
UUID=<DISK UUID>   /   btrfs   rw,noatime,compress=zstd,ssd,space_cache=v2,subvolid=5,subvol=/    0   1
# + line for bootloader, no mountpoint for my home folder
- /etc/default/grub line
GRUB_CMDLINE_LINUX="cryptdevice=/dev/vg/cryptroot:root root=/dev/mapper/root rootfstype=btrfs"
- output of "btrfs subvolume list -p /"
ID 256 gen 11 parent 5 top level 5 path var/lib/portables
ID 257 gen 12 parent 5 top level 5 path var/lib/machines

GOAL:
- Enable "easy" snapshots support (only root partition, my home directory excluded) using snapper

After reading the arch wiki and other resources, I'm still struggling to understand subvolumes and mountpoints.
Before messing up with my up and running installation, I would like to "dry-run" the needed changes but, without snapshot support working, I'm afraid I can end up in a unbootable system.

WHAT I THINK I SHOULD DO:
1. Create "@" subvolume (according to the output of "btrfs subvolume list" command, the "@" subvolume is missing) and mount it
--> btrfs subvolume create @
2. Create "@home" subvolume (to exclude it from snapshots) and "@snapshots"
--> btrfs subvolume create @home
--> btrfs subvolume create @snapshots
3. Create snapper initial configuration
--> snapper -c root create-config @

QUESTIONS:
Assuming my procedure is correct,
- How should I modify fstab to 1. modify the root mountpoint and 2. add the mountpoint for home and snapshots?
- Can I simply change "subvol=/" to "subvol=@" in fstab for root?
- Can I lose acces to root filesystem if I modify the subvol option? If yes, how can avoid this problem?

Thank you!