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Safe rm

rm: /: Not happening, bub.
 
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The textbook newbie mistake on a UNIX system is to inadvertently type “rm -rf /” as the superuser. The effect of this command is to remove every single file on every mounted drive (or as many as possible anyway, before the system crashes or the user realizes the terrible mistake and yanks the power cord out of the wall). Doing so is generally considered poor practice. You'd think it wouldn't happen all that often, but considering that just seeing that command typed out likely made anyone with any familiarity with UNIX cringe, it happens often enough that it's high time for a fix.

An easy solution to this problem would be to modify the “rm” program to raise an error if an attempt is made to remove the working directory, or any parent. This is as simple as applying a pattern match, comparing each of the target files (properly globbed and with paths expanded) to the output of “pwd”. In the (vanishingly unlikely) event that you really DID want to destroy the system for some reason, you'd have to “cd /” first, then “rm -rf *”.

I can't think of any reason you'd ever want to deliberately erase the working directory, but I grant that some idiot out there has probably written some script that depends on this functionality. Thus, for the sake of compatibility, you could also enable legacy mode by using the “--no-seriously-i-know-what-im-doing- and-i-really- want-to-do-this” option.

ytk, Sep 28 2012

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       This can be done quite simply by ailiasing the rm command with a shell script. This is Baked and Widely Known To Exist.   

       [-] for anything that restricts the ultimate, terrifing power of the SuperUser.
8th of 7, Sep 28 2012
  

       If you know enough to be able to alias rm to a shell script, you probably don't need this protection. Anyway, in single user mode (which is a prime opportunity for a clueless user to screw things up) your aliases are likely to be disabled anyway.   

       //[-] for anything that restricts the ultimate, terrifing power of the SuperUser.//   

       It's not a restriction. You can still do it if you REALLY want to. You just have to know the correct incantation. There are actually quite a few rm implementations nowadays that simply forbid operating recursively on / without some override switch (check your man page for details); this strikes me as a hack. The correct behavior for rm should be to abort if an attempt is made to remove the working directory, since doing so leaves the system in an inconsistent state and there's no legitimate reason for doing it anyway.
ytk, Sep 28 2012
  

       [marked-for-deletion] remapping the rm -rf command through the logon script is a common practice.   

       And even SU's do it, in case they step out to use the little sysadmin's room, or their fingers betray them after a long night out or summat.
FlyingToaster, Sep 28 2012
  

       So you're saying it never happens?
ytk, Sep 28 2012
  

       saying what never happens ? people blow their systems up all the time. And what [8th] said.   

       Anyways, among the various pieces of paper currently plugging holes in the wall and lining the birdcage are quite a few that proclaim I'm a UNIX sysadmin; some of them were even issued by people other than myself.   

       Even though at this point in time I can't remember a damned thing about UNIX, at least two of the courses mentioned that you should remap the rm-rf command first thing.
FlyingToaster, Sep 28 2012
  

       It's not such a common practice then, is it?
ytk, Sep 28 2012
  

       heh, anno edit interruptus.   

       It's a decent'ish idea, but one that root should be responsible for, not ANSI.   

       Ah, you mean cwd (I suppose occasionally reading more than the Title could be useful) ... extra flag or something I suppose, that could fit into a script.   

       Have you checked the Wikipedia entry for rm ?
FlyingToaster, Sep 28 2012
  

       It's clearly enough of a problem that various ways to prevent it that have been integrated into some versions of rm, as pointed out above. This solution is an alternate method that addresses the problem indirectly, and solves another problem (albeit a less serious one) besides.
ytk, Sep 28 2012
  
      
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