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  From: Alan Kennington <akenning@topology.org>
  To  : LinuxSA <linuxsa@linuxsa.org.au>
  Date: Thu, 31 May 2001 16:35:43 +0930

Re: Services file

On Thu, May 31, 2001 at 12:45:38PM +0930, Martin Stacey wrote:
> If I add a entry into the file /etc/services do I need to reboot my server
> in order to make the service (port) active?

Martin,

The reason the services file is not relevant to making
a port active is that it is just a name list.
It gives names to ports in the way that
the DNS gives names to IP host interfaces.

Thus you do not use the DNS to make a computer active!
On some SuSE machines, over 10,000 ports are listed in
the /etc/services file. I certainly hope these
ports are not all active!!!

The best way to think of the /etc/services file is that
it does for port numbers what the /etc/hosts file does
for IP addresses.
The difference is that the /etc/hosts file is extended
by the DNS, whereas there is nothing that extends the
/etc/services file in this way.

As Mark said, it's the inetd.conf file which makes ports active
- and there are other ways to make them active too, e.g.
by running daemons direct out of /etc/init.d scripts
instead of via inetd.conf, which is reads by inetd at start-up.

So if you want a service, you have to first find out what
software (usually a daemon) implements that service,
then determine if it can be run via inetd, and if so,
you can use inetd.conf. If not, you have to start it up
from one of them /etc/init.d scripts, which are usually
themselves turned on and off via system-wide config
scripts, like /etc/rc.config in SuSE and various /etc/sysconfig
files in RH.

Cheers,
Alan Kennington.

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