Arch Linux

Lesh13imtoostupid

Member

Registered: 2025-02-01

Posts: 7

System broke after deleting Timeshift snapshot while booted from it

Hi everyone,

My system once broke, and I booted it through a Timeshift snapshot via GRUB. After that, when I ran:

 mount | grep ' / ' 

I got:

 /dev/sdb3 on / type btrfs (rw,relatime,compress=zstd:3,ssd,discard=async,space_cache=v2,subvolid=307,subvol=/timeshift-btrfs/snapshots/2025-10-02_13-24-50/@) 

Then I deleted the snapshot that I was currently booted from (how i think). As a result, my system became unbootable. I had to boot again through a Timeshift snapshot via GRUB.

What is the proper way to recover from this situation, and how can I safely manage snapshots without breaking my system?

c>rust

Member

Registered: 2025-09-07

Posts: 23

Re: System broke after deleting Timeshift snapshot while booted from it

in my experience "#mount -a" dont remount root
and grup will use the current root and put it in /boot/grub/grub.cfg if not explicitly specify like below
in /etc/default/grub

GRUB_CMDLINE_LINUX_DEFAULT+="rootflags=subvol=@archlinux,degraded "

this is to avoid grub breaking when accidentally rebuild it from a snapshot
each param can only be specify once and will over write the previous one
this does not work

GRUB_CMDLINE_LINUX_DEFAULT+="rootflags+=subvol=@archlinux roorflags+=,degraded "

you don't need 'degraded' mount option that is for raid btrfs
don't use snapshots directly they are and should be readonly

sudo btrfs property get /.btrfsroot/snapshots/@archlinux/460/snapshot/
ro=true                                                                    

What is the proper way to recover from this situation, and how can I safely manage snapshots without breaking my system?

you didnt break the system you just haven't fix it
to make a snapshot the default snapshot run the below and replace with your own dir
and reboot
example for  snapper-rollback

$ snapper-rollback --dry-run 2
Are you SURE you want to rollback? Type 'CONFIRM' to continue: CONFIRM
2025-10-05 16:01:32,351 - INFO - mv /.btrfsroot/@archlinux /.btrfsroot/@archlinux2025-10-05T16:01
2025-10-05 16:01:32,351 - INFO - btrfs subvolume snapshot /.btrfsroot/snapshots/@archlinux/2/snapshot /.btrfsroot/@archlinux
2025-10-05 16:01:32,352 - INFO - btrfs subvolume set-default /.btrfsroot/@archlinux
2025-10-05 16:01:32,352 - INFO - [DRY-RUN MODE] Rollback to /.btrfsroot/snapshots/@archlinux/2/snapshot complete. Reboot to finish

you should have a file like btrfsroot for the fs root
move your current root snapshot
snapshot the (snapshot from your backup snapshots list) to replace (the previous root location) #readonly disable by default
set-default isn't necessary grub always have the subvol option set and will ignore it
reboot and grub should automatically use the new one as the default boot option

Last edited by c>rust (2025-10-05 09:24:29)