Re: [PLUG] "services" under Linux

[Wayne Dawson <jongalt@pinn.net>]

At 07:27 AM 3/11/03 -0500, you wrote:
> On Tue, Mar 11, 2003 at 06:57:44AM -0800, Wayne Dawson wrote:
> > What exactly is a service?
>
> A service is also refered to as a daemon under unix. Daemons typically
> run in user-land memory space, but can run as part of the kernel (system
> core) if necessary. They are usually triggered at startup from scripts
> running in /etc/init.d/.
>
> > I thought perhaps services are always processes that run whenever the
> > system is running, but that doesn't appear to be the case.
>
> If setup correctly that is the case.

I get the following list of "services" in the gui "Services" 
tool:  anacron, atd, autofs, crond, cyrus-imapd, gpm, ip6tables, ipchains, 
iptables, keytable, kudzu, mdmonitor, microcode_ctl, netfs, network, 
nfslock, protmap, privoxy, random, syslog, wine, xinetd>

At the command prompt, I typed "ps -ef | less".  Some "services" are 
listed, and some are not.
Those in the list that are listed (or have very similar names):  atd, 
crond, imapd, gpm, portmap, privoxy, syslogd, xinetd
Those that are *not* listed:  anacron, autofs, ip6tables, ipchains, 
iptables, keytable, kudzu, mdmonitor, microcode_ctl, netfs, network, 
nfslock, random, wine

Apparently a "service" is not precisely defined in terms of the software 
architecture, but simply means some software that in one way or another 
resides on the system for the purpose of providing a service (or services) 
to other software that may need it (or them).

>  Running `setup` as root in RH
> simply gives you the option to enable/disable the script to be run from
> init.d.

Ok, that appears to be the same list as in the gui "Services".

I'm familiar with the /etc/rc.d/init.d directory, and somewhat familiar 
with how those scripts work (running "/etc/rc.d/init.d/httpd restart", for 
example).  Are "services" defined in terms of /etc/rc.d?

>  However, the script will not run until you initialize it
> yourself by giving a command like:
>
> /etc/init.d/foo start
>
> > ...where to look to find out for sure what these various services do?
>
> The man pages are a good place to start. Type `man daemonname` or
> similar.

Many of them don't seem to have man pages.  For example when I type "man 
keytable", there's "No manual entry for keytable".  I get similar results 
for mdmonitor, netfs, network, nfslock.  However, I've found something on 
them from Google.

> > And which ones I can turn off?
>
> Well, that's entirely up to you. :-D

What I mean by this is which ones I can turn off and still retain the 
functionality that I need.  For example, when I start running apache, I 
will clearly need httpd running.  I want to turn things off that I'm not 
using, for security purposes.  But most of these services are things that I 
have found running even though I don't know exactly what they do.

Thanks,
Wayne 

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