start main, working folder: /usr/local/bin/backup_data
start main, time is:        20260918-1752
 == start new loop '10545', 20260918-175229 ==
20260918-180001: remove file 'main_lock'
 == start new loop '10546', 20260918-180003 ==
20260918-190001: remove file 'main_lock'
 == start new loop '10547', 20260918-190003 ==
20260918-200000: remove file 'main_lock'
 == start new loop '10548', 20260918-200001 ==
btrfs subvolume list . | grep -w "snapshot/ro_backup" 
 doesn't exist, after test
Create a readonly snapshot of 'subvolume/' in 'snapshot/ro_backup'
snapshot /home/linuxday/snapshot/ro_backup/ angelegt
btrfs subvolume list . | grep -w "snapshot/ro_backup" 
ID 721 gen 97595 top level 457 path snapshot/ro_backup
 existsi, delete
Delete subvolume 721 (no-commit): '/home/linuxday/snapshot/ro_backup'
  deleted
20260918-210000: remove file 'main_lock'
 == start new loop '10549', 20260918-210001 ==
