Single btrfs snapshot taking 21 GB on the drive

I currently have a snapshot that is taking 21GB space - almost same as my whole system. It is currently mounted and it is the single snapshot i have. I deleted all other snapshots (mounted snapshot cannot be deleted). I need advice on how to reclaim space used by this snapshot? Why is it taking so much space? I tried creating new snapshot - but the size of the new snapshot is as big (21GB) after deleting previous snapshot.

Here is my btrfs subvolume list / output:

ID 256 gen 29 top level 5 path @
ID 257 gen 444746 top level 256 path @/var
ID 258 gen 444684 top level 256 path @/usr/local
ID 259 gen 437973 top level 256 path @/srv
ID 260 gen 444139 top level 256 path @/root
ID 261 gen 436223 top level 256 path @/opt
ID 262 gen 414808 top level 256 path @/boot/grub2/x86_64-efi
ID 263 gen 248218 top level 256 path @/boot/grub2/i386-pc
ID 264 gen 444678 top level 256 path @/.snapshots
ID 266 gen 16266 top level 257 path @/var/lib/machines
ID 519 gen 444744 top level 264 path @/.snapshots/147/snapshot

And btrfs qgroup show -p / output:

Qgroupid Referenced Exclusive Parent Path
-------- ---------- --------- ------ ----
0/5 16.00KiB 16.00KiB - <toplevel>
0/256 16.00KiB 16.00KiB - @
0/257 16.16GiB 16.16GiB - @/var
0/258 640.03MiB 640.03MiB - @/usr/local
0/259 16.00KiB 16.00KiB - @/srv
0/260 1.36GiB 1.36GiB - @/root
0/261 973.38MiB 973.31MiB - @/opt
0/262 4.23MiB 4.23MiB - @/boot/grub2/x86_64-efi
0/263 16.00KiB 16.00KiB - @/boot/grub2/i386-pc
0/264 16.00KiB 16.00KiB - @/.snapshots
0/266 16.00KiB 16.00KiB - @/var/lib/machines
0/519 21.87GiB 21.87GiB - @/.snapshots/147/snapshot
1/0 0.00B 0.00B - <0 member qgroups>

ID 519 (snapshot 147) takes all the space. Is it safe to just remove it?

Filelight scan shows 23 GB of files in root folder. The other 21 GB are taken by this huge snapshot. I suppose it accumulated history of file changes since installation of the system. I would like to somehow purge this history to save space. At the moment deleting files from / does not free space on the drive. Looking for help, thanks in advance!

Show full output of snapper list. Always post computer text as preformatted (button </> in editor), otherwise it is difficult to read.

1 Like

Output of snapper list:

   # | Тип    | № предварительного снимка | Дата                    | Пользователь | Использовано места | Очистка | Описание            | Данные
-----+--------+---------------------------+-------------------------+--------------+--------------------+---------+---------------------+-------
  0  | single |                           |                         | root         |                    |         | current             |       
147* | single |                           | Чт 28 мар 2024 15:58:57 | root         |          21,87 ГиБ |         | writable copy of #0 |       

This snapshot is your whole system.

This is your current root subvolume. You do not have any snapshots, you only have your root filesystem.