[PLUG] "services" under Linux

[Wayne Dawson <jongalt@pinn.net>]

Hello everyone, I have a question about "services" under Linux, 
specifically RH8.0.  What exactly is a service?  I thought perhaps services 
are always processes that run whenever the system is running, but that 
doesn't appear to be the case.

In the RH8.0 gui (Gnome) I have an icon called "Start Here".  Within that I 
have one called "Server Settings" and within that "Services".  When I open 
that icon, I get a list of services, and the ones that are checked off (and 
my understanding of what they do) are:
- anacron - ?
- atd - daemon that runs commands at specified times (related to cron?)
- autofs - something to do with automounting file systems?
- crond - daemon that runs commands at specified times (related to atd?)
- cyrus-imapd - email server
- gpm - ?
- ip6tables - related to ip6 (I think not), or related to iptables 
(firewall software)?
- ipchains - firewall software?
- iptables - firewall software, an alternative to ipchains?
- keytable - keyboard remapping or crypto related?
- kudzu - ?
- mdmonitor - something to do with RAID?
- microcode_ctl - ?
- netfs - something related to network file systems
- network - something related to network setup
- nfslock - something related to locking files in network file systems
- portmap - something related to port forwarding?
- privoxy - ?
- random - pseudo random number generator
- syslog - service related to keeping logs of system activity
- wine - software that allows Windows executables to run under Linux
- xinetd - daemon that runs multiple netowork related things (some software 
can run under inetd/xinetd or on its own)

Can anyone tell me what defines a "service" under Linux and where to look 
to find out for sure what these various services do?  And which ones I can 
turn off?

Thanks,
Wayne

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