Delays on bad passwords considered harmful, accidental reboot edition
Here is what I just did to myself, in transcript form:
$ /bin/su Password: <type> [delay...] ['oh, I must have mistyped the password'] [up-arrow CR to repeat the su] bash# reboot <CR>
The normal root shell is bash and it had a bash history file with
'reboot' as the most recent command. When my
su invocation didn't drop
me into a root shell immediately I assumed that I'd fumbled the password
and it was forcing a retry delay (as almost all systems are configured
to do). These retry delays have trained me so that practically any time
su stalls on a normal machine I just repeat the
su; in a regular
shell session this is through my shell's interactive history mechanism
with an up-arrow and a CR, which I can type ahead before the shell
prompt reappears (and so I do).
Except this time around
su had succeeded and either the machine or the
network path to it was slow enough that it had just looked like it had
failed, so my 'up-arrow CR' sequence was handled by the just started
bash and was interpreted as 'pull the last command out of history
and repeat it'. That last command happened to be a 'reboot', because I'd
done that to the machine relatively recently.
(The irony here is that following my own advice I'd turned the delay off on this machine. But we have so many others with the delay on that I've gotten thoroughly trained in what to do on a delay.)
Comments on this page:Written on 24 November 2014.