[Chapter 7] 7.3 Starting and Stopping the System and Services

7.3 Starting and Stopping the System and Services

Using Linux commands, you can start and stop the system or start and start services, such as the Apache web server.

7.3.1 Starting and Stopping the System

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

7.3.2 Starting and Stopping Services

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.