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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: 5, Insightful) by pTamok on Tuesday February 09 2016, @11:14AM
There is a principle in security, which is the 'principle of least access' - you get the minimum access needed to do your job.
In this case, systemd opening the efi filesystem as rw when it didn't need to violates that principle: it should, as you point out later in your post, only open the filesystem for rw when it _needs_ to write, given what this pseudo filesystem is actually for.
If you think this argument is wrong, reflect on why some people prefer to use strongly typed languages. In principle, you can write everything in self-modifying assembler, and treat pointers as integers and have all sorts of fun - the point is not whether you can do it, the point is whether or not you should.
Having sane defaults is a good thing.