svn commit: r216823 - head/sbin/shutdown

[Erik Trulsson]

On Fri, Dec 31, 2010 at 07:00:58PM +0000, Alexander Best wrote:

[snip]

> another thought: running 'reboot' instead of 'shutdown -r now' *can* cause
> harm to the system, because an important rc.shutdown script wasn't executed.
> however running 'shutdown -r now' in single-user mode e.g. will cause a few
> sterr warnings; however it *cannot* cause any harm.

Oh, yes, it can! (And I have been burnt by it once, after which I got
very careful about not using 'shutdown -r now' from single user mode.)

Take a look at /etc/rc.d/mixer
At shutdown it saves the current state of the soundcard mixer values
into a file and at start it restores the mixer values from that file.
If you boot into single user mode the start function will of course not
be executed leaving the mixer values at their default values.  If you
then use 'shutdown' these default values are what will be saved,
overwriting whatever values had been saved before, while if you had
instead had used 'reboot' the old saved values would have been left
untouched.
If you never change the mixer values from their defaukt you won't notice
anything, but otherwise it might take a while to figure out why the
sound is at the 'wrong' volume.

This is one example I have found where bad things can happen if you use
'shutdown' when you should have used 'reboot'.  I am fairly sure that
there are other instances that I just haven't run into (yet.)




-- 
<Insert your favourite quote here.>
Erik Trulsson
ertr1013 at student.uu.se