the libvirt image has some problems
Dec 30 17:02:26 Tintin kernel: BTRFS info (device loop3): disk space caching is enabled
Dec 30 17:02:26 Tintin kernel: BTRFS info (device loop3): has skinny extents
Dec 30 17:02:26 Tintin kernel: BTRFS error (device loop3): bad tree block start, want 30539776 have 7795346113052941553
Dec 30 17:02:26 Tintin kernel: BTRFS error (device loop3): bad tree block start, want 30539776 have 113003311045498874
Dec 30 17:02:26 Tintin kernel: BTRFS warning (device loop3): failed to read tree root
Dec 30 17:02:26 Tintin root: mount: /etc/libvirt: wrong fs type, bad option, bad superblock on /dev/loop3, missing codepage or helper program, or other error.
Dec 30 17:02:26 Tintin kernel: BTRFS error (device loop3): open_ctree failed
Dec 30 17:02:26 Tintin root: mount error
Do you have a backup of it?
Also, does the following mean anything to you, since this all happened in quick succession?
Dec 30 17:05:31 Tintin sshd[2376]: Invalid user yamilet from 92.242.240.17 port 56708
Dec 30 17:05:31 Tintin sshd[2376]: Received disconnect from 92.242.240.17 port 56708:11: Bye Bye [preauth]
Dec 30 17:05:31 Tintin sshd[2376]: Disconnected from invalid user yamilet 92.242.240.17 port 56708 [preauth]
Dec 30 17:06:20 Tintin sshd[3862]: Received disconnect from 112.162.191.160 port 33264:11: Bye Bye [preauth]
Dec 30 17:06:20 Tintin sshd[3862]: Disconnected from authenticating user root 112.162.191.160 port 33264 [preauth]
Dec 30 17:06:43 Tintin sshd[4599]: Invalid user pascal from 164.132.57.16 port 40849
Dec 30 17:06:43 Tintin sshd[4599]: Received disconnect from 164.132.57.16 port 40849:11: Bye Bye [preauth]
Dec 30 17:06:43 Tintin sshd[4599]: Disconnected from invalid user pascal 164.132.57.16 port 40849 [preauth]
Dec 30 17:10:30 Tintin sshd[11798]: Received disconnect from 49.234.30.113 port 45073:11: Bye Bye [preauth]
Dec 30 17:10:30 Tintin sshd[11798]: Disconnected from authenticating user mail 49.234.30.113 port 45073 [preauth]
Dec 30 17:12:02 Tintin webGUI: Successful login user root from 192.168.88.109