Red Hat's response to my system-config-samba rhel6 issue

[Richard Pieri]

On Dec 20, 2010, at 6:20 PM, Tom Metro wrote:
> 
> The gist of it, as I recall, is that the SysV approach is sequential and
> only has the granularity of runlevels (which, except for a few, were
> mostly unused).

Actually, most are used: 0 = reboot, 1 or S = single user, 3 or 4 = multi-user with networking, 4 or 5 = multi-user with networking and X server, and 6 = reboot.  But as you say, the init method, be it System V or BSD, is sequential both startup and shutdown.

FWIW, OS X uses launchd instead of init, cron and several other tools.  It provides parallel service start, time-based service start, and what I find very useful is even-based start.  The last is something that Linux does not have that I'm aware of.  This part of launchd can be set to monitor a file or device for changes and start or stop a service when the change happens.  So, for example, I could have a launch agent set to watch for a device mount, and automatically kick off a backup when that device is connected.  Or, for example, I could have it watch for changes to /etc/resolv.conf and run a configuration script that sets the default printer, mounts local network shares, etc.  It's *very* useful.

--Rich P.