[Emergency Mode] System won't boot after deleting Snapper snapshots (B

veerendra · 2026-02-25 14:06:16

Hi Arch community,

I need help recovering my system from emergency mode after deleting Snapper snapshots.

## System Setup:
- Arch Linux
- Btrfs filesystem with Snapper
- NVMe drive (nvme0n1p2 = 475GB root, nvme0n1p1 = 1GB boot)
- Subvolume layout: @, @home, @log, @pkg, @/.snapshots, @home/.snapshots

## What I Did:
I ran this command to delete old snapshots:
sudo snapper -c home delete 400-1400
sudo snapper -c root delete 400-1400

## Problem:
After reboot, the system drops to emergency mode with errors like:
- "Dependency failed for Local File Systems"
- "Dependency failed for /var/log"
- "Dependency failed for /home"
- "Dependency failed for /swap"
- "Timed out waiting for device /dev/disk/by-uuid=..."

## What I've Tried:
1. Booted from Arch Live USB
2. Mounted Btrfs top level with: `mount -o subvolid=5 /dev/nvme0n1p2 /mnt`
3. Listed subvolumes with: `btrfs subvolume list /mnt`
4. Found that snapshots 749, 750, 1150, etc. still exist in the subvolume list

current /etc/fstab had
UUID=099bb245-f132-441c-b8bc-b131696c381d / btrfs rw,relatime,compress=zstd:3,ssd,discard=async,space_cache=v2,subvol=@ 0 0
UUID=099bb245-f132-441c-b8bc-b131696c381d /home btrfs rw,relatime,compress=zstd:3,ssd,discard=async,space_cache=v2,subvol=@home 0 0
UUID=099bb245-f132-441c-b8bc-b131696c381d /var/log btrfs rw,relatime,compress=zstd:3,ssd,discard=async,space_cache=v2,subvol=@log 0 0
UUID=099bb245-f132-441c-b8bc-b131696c381d /var/cache/pacman/pkg btrfs rw,relatime,compress=zstd:3,ssd,discard=async,space_cache=v2,subvol=@pkg 0 0
UUID=F441-C43A /boot vfat rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=ascii,shortname=mixed,utf8,errors=remount-ro 0 2
UUID=099bb245-f132-441c-b8bc-b131696c381d /swap btrfs noatime,nodatacow,compress=no,subvolid=266 0 0
/swap/swapfile none swap sw 0 0

Screenshots:

Boot error screen
fstab content
btrfs subvolume list
Emergency mode errors

seth · 2026-02-25 22:26:05

The timeout in https://ibb.co/cSXVY3ZZ is a late response from the btrfs sync?

You obviously still can mount the root partition so chances are that booting and installed kernel / initramfs are just out of sync.

btrfs check /dev/nvme0n1p2 # to see whether the partition has glaring errors…
mount -o subvol=@ /dev/nvme0n1p2 /mnt
ls -l /mnt/boot
mount /dev/nvme0n1p1 /mnt/boot
ls -l /mnt/boot
ls -l /mnt/lib/modules

If the above doesn't show obvious problems, try to mount w/o the quiet parameter.

In future maybe use "-s" w/ snapper (I guess you rebooted quickly after the snapper calls?)

veerendra · 2026-02-25 22:40:19

Sir see this https://ibb.co/YBw0j6KK

seth · 2026-02-25 22:53:52

btrfs check --mode lowmem /dev/nvme0n1p2

Otherwise at least see whether you can mount the partition, what's in it - and also verify the UUID w/ "lsblk -f"

***UNDER NO CIRCUMSTANCES*** USE THE BTRSFS REPAIR IN LOWMEM MODE!

veerendra · 2026-02-26 07:25:46

Tq sir problem sloved and now my laptop is again into normal state but thing is that btrfs-clean is still running and it didnt cleaned any snapshots so again its same emercecy mood happned so its seems like aloop

seth · 2026-02-26 09:08:00

problem solved

How? What was the actual problem?
https://wiki.archlinux.org/title/Genera … way_street - and also because

btrfs-clean is still running and it didnt cleaned any snapshots so again its same emercecy mood happned

Is the system now however running again?
https://wiki.archlinux.org/title/Snappe … _snapshots
Please provide the list of configs and existing snapshots for each config.
Also what exactly triggers the btrfs-clean thread and how long is it "still running" (w/ the same PID!)
Does it time out or use an exceptional amount of cpu time?

Arch Linux

#1 2026-02-25 14:06:16

[Emergency Mode] System won't boot after deleting Snapper snapshots (B

Screenshots:

#2 2026-02-25 22:26:05

Re: [Emergency Mode] System won't boot after deleting Snapper snapshots (B

#3 2026-02-25 22:40:19

Re: [Emergency Mode] System won't boot after deleting Snapper snapshots (B

#4 2026-02-25 22:53:52

Re: [Emergency Mode] System won't boot after deleting Snapper snapshots (B

#5 2026-02-26 07:25:46

Re: [Emergency Mode] System won't boot after deleting Snapper snapshots (B

#6 2026-02-26 09:08:00

Re: [Emergency Mode] System won't boot after deleting Snapper snapshots (B

Board footer