A number of users have reported that running "rm --no-preserve-root -rf /" not only deletes all their files (as expected), but also permanently bricks their computers (which is not). Tracing the issue revealed that the ultimate cause was that SystemD mounted the EFI pseudo-fs as read-write even when this FS was not listed in fstab, and deleting certain files in this pseudo-fs causes certain buggy, but very common, firmware not to POST anymore. A user reported this bug on SystemD's GitHub issue tracker, asking that the FS be mounted read-only instead of read-write, and said bug was immediately closed as invalid. The comment thread for the bug was locked shortly after. Discuss.
Links:
https://github.com/systemd/systemd/issues/2402
http://thenextweb.com/insider/2016/02/01/running-a-single-delete-command-can-permanently-brick-laptops-from-inside-linux/
(Score: 2) by maxwell demon on Wednesday February 10 2016, @07:28AM
I just checked, and to my surprise you're right. However that was not always the case; I explicitly checked in the fstab of an old OpenSUSE installation that my memory is not wrong; its fstab indeed does contain entries for proc and sys. When did they change this? I consider the old way to be the right way.
The only things that should be mounted by default are those things needed to explicitly mount the rest. Everything else should be mounted only via fstab, no matter how fundamental it is.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 1, Informative) by Anonymous Coward on Monday February 15 2016, @03:12AM
Maybe your initramfs mounts those?
https://stackoverflow.com/questions/34326854/if-there-is-no-sysfs-in-etc-fstab-how-sysfs-is-mounted [stackoverflow.com]