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I noticed in the documentation for rm as obtained by rm --help the following flag:

--no-preserve-root  do not treat `/' specially

What does this mean? Is it actually possible to delete the root directory, apart from its contents? What consequences would that have?

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Yes, they put in place a protection from people who try rm -rf /. They put that in place because yes, you can and you're system will be useless. – nerdwaller Jan 28 '13 at 17:02
In my understanding, rm -rf / deletes the contents of the root directory; but wouldn't the root directory itself still exist? – gerrit Jan 28 '13 at 17:03
@gerrit: Yes, it would. But this command is precisely why the "preserve root" mode was added: rm refuses to operate recursively on / unless you add the --no-preserve-root option. – grawity Jan 28 '13 at 17:04
up vote 11 down vote accepted

You cannot delete the root directory itself. However, you can use rm's recursive mode to delete everything in that directory – the infamous rm -rf / command.

The "preserve root" mode stops rm from recursively operating on the root directory:

$ sudo rm -rf /
rm: it is dangerous to operate recursively on ‘/’
rm: use --no-preserve-root to override this failsafe

The --preserve-root option was added to GNU rm in 2003 (commit 9be74f6f125b2be), and was made the default behavior in 2006 (commit aff5a4f2ab86f).

Some say it is because pranksters in #ubuntu kept telling newbies to run rm -rf / – and many did. Some say it is because it is too easy to mistype rm -rf / tmp/junk. Some say it is to prevent accidents when running rm -rf $dir/ when $dir is empty. All we know is, he's called th

Either way, it is part of POSIX requirements nowadays. Solaris rm also has similar protection, as does OpenBSD.

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Did you actually dare to type that for real? – gerrit Jan 28 '13 at 17:05
Linux is cheap, as are old computers. Admit that you've done it on a decommissioned system to see how to quickly create disk space. And the answer is yes. – Fiasco Labs Jan 28 '13 at 17:19

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