Re: networking in rcS
On Mon, 11 Jun 2001, Miquel van Smoorenburg wrote:
> > How's that?
> >
> > Does init kill all running processes when going to single user? (Guess you
> > should know, since you wrote it ;-)
>
> Yes. /etc/rc1.d/S20single
Aha.
Well, guess I learned something new here ;-)
> > > It sure is. No daemons run in single user mode, so remote access
> > > is impossible.
> >
> > I'm not sure, but since most daemons spawn another instance of themselves
> > to actually handle an incoming connection, wouldn't you say that an
> > existing connection could stay alive when the "main" daemon gets killed?
>
> *all* daemons are killed. There's just init running and some kernel
> threads. All other processes have been sent to the eternal bitfields.
Since there is something as killall5, they are. I just assumed
start-stop-daemon was used to kill all running daemons, which seems to be
wrong.
> > It shouldn't (and should go into zombie state), but I've seen situations
> > in which "kill -9" to a hung process simply doesn't work
>
> I know of only 2 situations in which that can happen:
>
> 1) kernel bug
> 2) process hung on an NFS mount
I've seen this happen to something else too -- not NFS, and too many
kernel versions to be a bug as well -- but I can't recall what it was.
Anyway, it doesn't matter. You're right, and I'm wrong ;-)
> > or where a
> > zombie process stayed alive for several minutes after its parent got
> > killed.
>
> Zombies aren't alive. Zombies are dead. A zombie is a child process
> that *still has a parent* but which is dead - however the parent
> hasn't wait()ed for it to collect its exit status
>
> A zombie without a parent doesn't exist. Unix 101
I won't bet on this one.
> > > Say you fscked up the box and bring it to single user mode to fix
> > > things, it is very handy (usually essential) to be able to use
> > > ftp to access debian packages, to save logfiles, what have you.
> >
> > If it's really necessary (which, in this case it is), it's still possible
> > to bring up the network manually. I see no need to leave it up.
>
> Yes - what if your box is diskless. Or, /usr is NFS mounted. I don't
> see a reason to explicitly bring the network down, it simply makes
> no sense.
After your arguments, I agree.
--
wouter dot verhelst at advalvas in belgium
Try does not exist. Believe that you will do it, else you will fail.
-- Luke Skywalker,
in the trilogy "The Jedi Academy", Kevin J. Anderson
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