They say rm command defaults to the option --preserve-root. Is that right?

Otherwise I should put the line

alias rm='rm --preserve-root'`

in ~/.bashrc to make that option happen without typing it every time I run the rm command. To confirm this I ran type rm, and got rm is hashed (/bin/rm).

I expected rm is aliased to rm --preserve-root. Does anyone know what's going on with the rm command?

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    sorry I have no idea who "they" are, but I think you'll find it depends on your kernel & shell/bash version. I know some of the systems I use (which are still supported) don't have --preserve-root on rm. – guiverc Dec 1 '17 at 12:34
  • Oh, I said they cause I'm reading a book, whose name is like Ubuntu Unlished 2017 or something. I thought saying specific book name makes me look like book seller, so I did like that. My ubuntu version is Ubuntu 16.04. I still want to know how to confirm whether --preserve-root is default or not. – Smile Dec 1 '17 at 12:42
  • At least for me I get for sudo rm -r / the following message: rm: it is dangerous to operate recursively on '/' and rm: use --flag-i-wont-mention to override this failsafe – Videonauth Dec 1 '17 at 12:44
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    This is also present in the manpage for rm. – user595510 Dec 1 '17 at 12:57
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    @guiverc It has nothing to do with the kernel, or your shell (bash or otherwise). It's a default option in GNU rm since some years, which is a separate program from your shell. (It's in coreutils in Debian and Ubuntu). – marcelm Dec 1 '17 at 13:46

rm is not being aliased to rm --preserve-root, but the option is selected by default in the rm binary.

From the manpage of rm in Ubuntu 17.10, you can find the following details of the --preserve-root and --no-preserve-root options:

          do not treat '/' specially

          do not remove '/' (default)
  • I have read man page, but I totally missed the "(default)". Thanks for the reply. BTW when you mention 'rm binary', did you mean rm is programmed in that way?? – Smile Dec 1 '17 at 12:56
  • @Smile Yes, that's what it means. – user595510 Dec 1 '17 at 12:57

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