- PR_SET_MM_MAP is required (the kernel version >= 3.18)
- shared memory can't be dumped from a non-root user
Error: Can't open 24/map_files/7f72d1687000-7f72d1688000 on procfs: Operation not permitted
- criu restore doesn't work
Error: Write 29 to sys/kernel/ns_last_pid: Operation not permitted
- criu restore works in a new userns only if setgroups is set to "allow"
pie: 235: Error (criu/pie/restorer.c:172): Can't setup supplementary groups
||FIXME: describe checkpoint/restore as an unprivileged (non-root) user.