Following circumstance caused the strange behavior: When the root disk went full, I tried to free disk space by deleting the content of the /tmp directory (sorry, I forgot to mention this).
... and when using apt-btrfs-snapshot and doing a 'apt update' the btrfs partition will be mounted under /tmp/apt-btrfs-snapshot-* . So deleting /tmp actually deleted the root disk what crashed the system. ** Changed in: ubuntu Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2063029 Title: Symlinks /bin, /sbin, /lib ... disappeared after root disk full To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+bug/2063029/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs