Using Linux commands, you can start and stop the system or start
and start services, such as the Apache web server.
Generally, you start your system by turning on its
power. However, you can use a Linux command to cause a system to
restart itself. If you enter the command:
shutdown -r now
the system will immediately begin to shut down. Once it's shut
down, it will reboot. If you want to provide a delay before commencing
the shutdown, use this form of the command:
shutdown -r +
mm
where
mm gives the number of minutes
until the shutdown commences. The command displays a message to
system users who have active shells displaying a command prompt. After
commencement of a shutdown, users cannot initiate new login
sessions.
If you want to halt the system, that is, shut down the system
without causing it to reboot, use the command:
shutdown -h now
Services are daemon programs that run without an associated
console. They listen for network connections from clients, which
request them to perform an action or provide information.
Table 7.1 describes some of the most important
services.
Table 7.1: Important Services
|
Service |
Function |
|
apache |
Web server |
|
atd |
Runs commands at predefined times. |
|
cron |
Runs commands at predefine times; offers more flexibility than
atd. |
|
exim |
Mail transfer agent. |
|
gpm |
Provides cut and paste to virtual consoles. |
|
lpd |
Controls the printer. |
|
netbase |
Basic networking services (
inetd and
portmap). |
|
netstd_init |
Network routing (
routed). |
|
netstd_misc |
Miscellaneous networking services. |
|
nfs-server |
Network file system (
nfsd). |
|
samba |
Microsoft-compatible networking (
smbd and
nmbd). |
If a network services fails, you may want to restart it without
rebooting your system. To do so, you can enter a command such as
this:
/etc/init.d/
service start
where service gives the name of the service, as shown in
Table 7.1.
If you want to stop a service, use a command such as
this:
/etc/init.d/
service stop
If a service is behaving erratically, you may be able to
stabilize it by stopping and restarting it:
/etc/init.d/
service stop
/etc/init.d/
service start
Pause a few seconds before entering the start command to give
the service time to come to a smooth stop.
