Rob Landley
rob at landley.net

Thu Dec 9 15:45:39 UTC 2010

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On Tuesday 30 November 2010 15:58:00 David Collier wrote:
> I see that busybox spreads it's links over these 4 directories.
>
> Is there a simple rule which decides which directory each link lives
> in.....
>
> For instance I see kill is in /bin and killall in /usr/bin.... I don't
> have a grip on what might be the logic for that.

You know how Ken Thompson and Dennis Ritchie created Unix on a PDP-7 in 1969?  
Well around 1971 they upgraded to a PDP-11 with a pair of RK05 disk packs (1.5 
megabytes each) for storage.

When the operating system grew too big to fit on the first RK05 disk pack (their 
root filesystem) they let it leak into the second one, which is where all the 
user home directories lived (which is why the mount was called /usr).  They 
replicated all the OS directories under there (/bin, /sbin, /lib, /tmp...) and 
wrote files to those new directories because their original disk was out of 
space.  When they got a third disk, they mounted it on /home and relocated all 
the user directories to there so the OS could consume all the space on both 
disks and grow to THREE WHOLE MEGABYTES (ooooh!).

Of course they made rules about "when the system first boots, it has to come up 
enough to be able to mount the