On Mon, 8 Aug 2016, Ivan Sizov wrote:

I'd ran "rm -rf //" by mistake two days ago. I'd stopped it after five

Out of curiosity, what version of coreutils is this? The --preserve-root 
option is the default for quite some time now:

Don't include dirname.h, since system.h does it now.
(usage, main): --preserve-root is now the default.
2006-09-03 02:53:58 +0000

http://git.savannah.gnu.org/cgit/coreutils.git/commit/src/rm.c?id=89ffaa19909d31dffbcf12fb4498afb72666f6c9

Even coreutils-6.10 from Debian/5 refuses to remove "/":

$ sudo rm -rf /
rm: cannot remove root directory `/'

Christian.
-- 
BOFH excuse #243:

The computer fleetly, mouse and all.