Autostart
When your machine turns on or reboots, you want certain things to happen automatically. If the 'machine' is a web server hosting websites defined by Apache and also a database server running MySQL, then naturally you would want Apache and MySQL to start automatically. In SysV-style systems that still use init and the rc.d run levels, you can use either chkconfig[1] (RedHat and derivatives) or sysv-rc-conf for Debian variants to make that permanent.
List services
So what are the services controlled by 'init' scripts?
# the easy way
ls -l /etc/rc.d/init.d/
# using chkconfig
chkconfig --list
# for newer systemd controlled systems
systemctl list-units
Here is an example list of the services you might find on your machine:
- NetworkManager
- acpid
- anacron
- atd
- auditd
- autofs
- avahi-daemon
- avahi-dnsconfd
- bluetooth
- capi
- clvmd
- cman
- cmirror
- conman
- cpuspeed
- crashplan
- crond
- cups
- dc_client
- dc_server
- dnsmasq
- dund
- ebtables
- firstboot
- gfs
- gfs2
- gpm
- haldaemon
- hidd
- hplip
- httpd
- ip6tables
- ipmi
- iptables
- irda
- irqbalance
- iscsi
- iscsid
- isdn
- kdump
- kudzu
- libvirt-guests
- libvirtd
- lm_sensors
- luci
- lvm2-monitor
- mcstrans
- mdmonitor
- mdmpd
- messagebus
- modclusterd
- multipathd
- mysql51-mysqld
- mysql55-mysqld
- mysqld
- nagios
- netconsole
- netfs
- netplugd
- network
- networker
- nfs
- nfslock
- nginx
- nrpe
- nscd
- ntop
- ntpd
- nxserver
- oddjobd
- openais
- openwsmand
- pand
- pcscd
- piranha-gui
- portmap
- postfix
- postgresql
- psacct
- pulse
- qdiskd
- rawdevices
- rdisc
- readahead_early
- readahead_later
- restorecond
- rgmanager
- rhnsd
- rhsmcertd
- ricci
- rpcgssd
- rpcidmapd
- rpcsvcgssd
- rsyslog
- saslauthd
- sblim-sfcb
- scsi_reserve
- setroubleshoot
- slinksc
- smartd
- snmpd
- snmptrapd
- squid
- sshd
- svnserve
- syslog
- tomcat5
- tux
- vncserver
- wdaemon
- winbind
- wpa_supplicant
- xfs
- xinetd
- ypbind
- yum-updatesd
Enable/Disable/Start/Stop/Status a service
# for older systems using System V style init
chkconfig apache on|off|start|stop|status
# for newer systemd controlled systems
systemctl enable|disable|start|stop|status <servicename>.service