Deleting Snapshots of the root File System

Note:

A snapshot can't be deleted if it's set as the default ID for a subvolume. Deleting a snapshot while it's in use as the root file system might cause system failure and requires a hard physical reset. Before deleting a snapshot that's set as the default subvolume for the root File System, change the default ID and reboot the system, for example:

sudo btrfs subvolume set-default 258 /
reboot

To delete a snapshot, do the following:

Mount the top level of the file system.
For example, run:
```
sudo mount -o subvolid=5 /dev/sda2 /mnt
```
Use the btrfs subvolume delete command to delete the snapshot.
```
sudo btrfs subvolume delete /mnt/.snapshots/root-snapshot1
```

Unmount the top level of the file system:

sudo umount /mnt

The list of subvolumes relative to the root file system now doesn't include snapshots/root-snapshot1.

sudo btrfs subvolume list /

ID 256 gen 1332 top level 5 path boot
ID 258 gen 1349 top level 5 path root
ID 259 gen 1309 top level 5 path home
ID 261 gen 1309 top level 258 path var/lib/portables