On Thu, Jul 06, 2000 at 09:56:11AM +0930, Mark Phillips wrote: > Hi, > > I am a little confused about how the external services thing works. > > Suppose for example you want to allow exteral rlogins to your > computer. I presume you modify the inetd.conf file to include the line: > > login stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.rlogind > > Now when is this file read? Is it only when you do something like > "/etc/init.d/inetd restart", or is it whenever an external machine > asks to connect to one of your ports?
It's read every time inetd starts, or you send inetd a "HUP" signal
like "kill -hup `cat /var/run/inetd.pid`" or "/etc/init.d/inetd
reload"
> Now am I right in thinking that there is not an rlogin daemon running
> all the time, listening for rlogin connections? I think what happens
> is that inetd listens for connections, and then if it receives one for
> rlogin, it executes in.rlogind --- one for each incomming connection
> --- is that right?
Sort of. First it executes /usr/sbin/tcpd which applies rules found
in /etc/hosts/allow and /etc/hosts.deny.
> Now the above is all correct, I'm still a little confused, because
> what about smtp? Currently I have the following line in inetd.conf
>
> #disabled#smtp stream tcp nowait mail /usr/sbin/exim exim -bs
>
> So it is disabled, yet mail still works on my system! Is this because
> it is handled through a different mechanism? I notice that I have the
> following process:
It's disabled in inetd ... doesn't mean it's disabled for the system!
> mail 286 0.0 0.3 2324 204 ? S Jun24 0:00 /usr/sbin/exim -bd -q30m
^^
"Be a Daemon" - exim opens port 25 itself and forks off children as
connections arrive. inetd is out of the picture altogether.
> Which I am guessing does the job instead of inetd? If so, why do it
> this way instead of through inetd?
Daemons are fast - you skip the overhead of inetd! On the other hand,
sometimes inetd gives you more security (it depends on the service).
> Any clarifications of my understanding of these things would be much
> appreciated.
Hope this helps.
--
Nathan Norman "Eschew Obfuscation" Network Engineer
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