Brain Teaser

[Joe Smith]

In article <1990Oct6.042126.24228 at athena.mit.edu> wchuang at athena.mit.edu (Mithrandir) writes:
>>mv /bin/sh /bin/sh.in		# now you're stuck
>On a single-machine, you could reboot the workstation, bring it up in
>single-user mode, and move /bin/sh.bin back to /bin/sh.

You can only do that on a system where the single-user shell is something
other than /bin/sh.  One such example is SunOS 4.0 and later.  When a Sun
system comes up single-user, the kernel starts up /sbin/init which invokes
/sbin/sh.  (/usr/bin/sh is not used since /usr is often NFS mounted.)
-- 
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