[linux-help] Re: understanding daemons

[John Reinke <jmreinke@xxxxxxxxx>]

Hmmm... Did you light a bunch of candles and turn out the lights before
invoking the daemon? Just Kidding!

In a nutshell, any daemon that needs to be started or stopped should have a
script in /etc/init.d to perform those tasks when needed. However, items in
that directory aren't run directly. Depending on the runlevel the system
changes from and to, those scripts are called from within the /etc/rcX.d
(where X is the runlevel) directories. Those directories contain links to
the scripts in /etc/init.d, and the links starting with S (start) are
executed when entering that runlevel and K (kill) are executed when leaving
that runlevel. The number in the link name controls the order in which they
are executed.

If you use Debian, you can read about this in /usr/doc/debian-policy. I
suggest also reading the man pages for update-rc.d and inittab. The former
is used to create the links I mentioned above and the latter controls which
runlevel the system initially boots into.

That should be helpful for getting your DHCP server to start automatically.

John

>I'm trying to better understand daemons and how they
>work with Linux.  I just finished setting up a DHCP
>server on my 486 Linux box.  I got everything setup to
>go (/etc/init.d/dhcp, dhcpd.conf & dhcp.leases)  The
>man pages said I had to "invoke" the daemon, but I
>didn't know how to "invoke" anything.  I thought maybe
>I could set the ball in motion by rebooting
>instead...but that didn't work.  I finally learned to
>invoke the daemon by typing "dhcpd start eth0".  At
>that point, I was wondering if the daemon would still
>be running after a reboot or if I'd have to invoke it
>every time I started the machine.  The daemon was
>running after a reboot.  I don't understand why the
>reboot didn't work.  The dhcp file in init.d is what
>causes dhcp to start during a boot, right?  So why
>didn't that work when the daemon hadn't yet been
>invoked?  I thought a "dhcpd start" was nothing more
>than a manual way to do what's done automatically
>during a boot.



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