[PLUG] /bin/bash: Permission denied

Keith Lofstrom keithl at kl-ic.com
Mon Jan 16 04:33:06 UTC 2012


Doing some sysadmin on my wife's work computer.  scp'ed some
files from another machine - and put an extra space in the wrong
place.  No visible damage, except all of a sudden, all the
commands stopped working in the "keithl" windows.  I had an
open root window (bad security, but it saved my ass this time)
and I could run everything as root.  I could even create some
new xterms (as root) for experements.  But when I tried to 
"su - keithl" I got:

  Could not chdir to home directory /home/keithl: Permission denied
  /bin/bash: Permission denied

YIKES! 

It is now three hours later, there are a lot of dents in the wall
and in my forehead, and I found the "d-oh!" answer.  It turns
out that the borked scp had changed the permissions of "/" -
the root directory itself - from 755 to 750 .  Thus making the
entire filesystem unreadable to anyone besides root.  I changed
it back to 755, and everything is back to expectations. 
Fortunately, I did not do too much irreversable damage while
frobbing and fussing.

So, kiddies, when this happens, do an "ll -ad /" and pay attention.
Root is a directory, with permissions like everything else.  If it
ever gets set to 750, there goes user functionality.  If it gets
set to 777, there goes your security.

Keith

-- 
Keith Lofstrom          keithl at keithl.com         Voice (503)-520-1993
KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs



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