On Wed, Oct 20, 1999 at 02:32:35PM +1000, raf wrote:
> On Tue, Oct 19, 1999 at 09:13:15PM +0200, Niels M?ller wrote:
> > Thayne Harbaugh <[EMAIL PROTECTED]> writes:
> >
> > > daemonization cannot be done be a shell script - it has to happen
> > > in the executeable. It is quite easy to do, however:
> >
> > Ok, I guess I should drop that idea. Even if I'm not sure I see why it
> > can't be done (at least on this machine, there's a setsid program that
> > should be usable from a script).
> >
> > > cd /
> > > fork/exec - parent exits
> > > set sid
> > > close all file descriptors (more of a concern on sysV)
> > > fork/exec - parent exits
> > > syslog all messages
> > >
> > > It's also a good idea to add some commandline args to tell it
> > > to not fork/exec and become a daemon and also dump messages to
> > > stdout/stderr instead of syslog.
>
> preventing core dumps is also a good idea for security,
> and creating a locked pid file to prevent multiple instances running,
> and leaving stdin/out/err open to /dev/null for stray library calls
> that want them to be open to something. also, the second fork/exec
> is only usefdul on svr4 (to prevent gaining a controlling terminal).
> on bsd it doesn't prevent it. you still need to use O_NOCTTY when
> opening terminals.
>
> > Another case is if the deamon is started directly by init (listed in
> > inittab). In this case it's a bad idea to fork and let the parent
> > exit. Perhaps
> >
> > if ( (getppid() != 1) && fork() ) exit(0);
> >
> > should do that trick.
>
> there's shouldn't be any problem as long as init hasn't been told
> to respawn it.
>
> another case is daemons started by inetd. if stdin/out/err are open
> to a socket, the daemon was invoked by inetd and is already in an
> appropriate context for a daemon so the fork/exec/setsid... isn't
> necessary and the closing of file descriptors would be very bad.
>
> > > If you have any questions concerning the above - let me know.
> >
> > Thanks.
> >
> > > Hmmm. I guess I'm just as liable telling you how to do it as
> > > writing the code - maybe I'll just write some code . . . I dunno
> > > (stinking munition laws).
> > >
> >
> > Somebody else just offered to write the code. So we'll see what
> > happens.
>
> i've got the code at home (but i'm at work now).
> i can mail it to you later today if you want it.
> it doesn't handle the inetd case but if it needs
> to it can be added in a few seconds.
>
> raf
now it handles the init and inetd cases.
http://www.zip.com.au/~raf2/lib/software/daemon
raf
