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Service Management Tools: chkconfig and redhat-config-serivces

On Red Hat, redhat-config-services and the

chkconfig command provide simple interfaces you can use to choose what servers you want started up and how you want them to run. You use these tools to control any daemon you want started up, including system services such as

cron , the print server, remote file servers for Samba and NFS, authentication servers for Kerberos, and, of course, Internet servers for FTP or HTTP. Such daemons are referred to as services, and you should think of these tools as managing these services. Any of these services can be set up to start or stop at different runlevels.

These tools manage services that are started up by scripts in the

/etc/rc.d/init.d directory. If you add a new service, both

chkconfig and redhat-config-services can manage it. As described in the following section, services are started up at specific runlevels using startup links in various runlevel directories. These links are connected to the startup scripts in the

init.d directory. Runlevel directories are numbered from 0 to 6 in the

/etc/rc.d directory, such as

/etc/rc.d/rc3.d for runlevel 3 and

/etc/rc.d/rc5.d for runlevel 5. Removing a service from a runlevel only changes its link in the corresponding runlevel

rc.d directory. It does not touch the startup script in the

init.d directory.

redhat-config-services

With the Red Hat redhat-config-services utilities, you can simply select from a list of commonly used services those that you want to run when your system boots up. You can access redhat-config-services from the Services icon in the Server Settings window or menu, located under System Settings. redhat-config-services lets you start, stop, and restart a server, much like the

service command (see Figure 20-1). redhat-config-services provides a GNOME GUI interface for easy use. It displays a list of your installed servers, with checked check boxes for those currently chosen to start up. You can start, stop, or restart any particular service by selecting it and choosing either Start Service, Stop Service, or Restart Service from the Action menu.

Figure 20-1: redhat-configservices

You can also set startup runlevels for services, just as you can with

chkconfig , though you are limited to levels 3, 4, and 5. The list of checked entries differs depending on the runlevel you choose from the Edit Runlevel menu. In effect, you are choosing which services to start at a given runlevel. The default is runlevel 5, the GUI startup level. You may want a different set of services started or stopped for runlevel 3, the command line startup level. In that case, you would select Runlevel 3 from the Edit Runlevel menu to display the services with selected check boxes for runlevel 3.

chkconfig

You can specify the service you want to start and the level you want to start it at with the

chkconfig command. Unlike other service management tools,

chkconfig works equally well on standalone and

xinetd services. Though standalone services can be run at any runlevel, you can also turn

xinetd services on or off for the runlevels that

xinetd runs in. Table 20-3 lists the different

chkconfig options.

Listing Services with chkconfig

To see a list of services, use the

--list option. A sampling of services managed by

chkconfig are shown here. The on or off status of the service is shown at each runlevel.

xinetd services and their status are also shown:

chkconfig -list
dhcpd  0:off 1:off 2:off 3:off 4:off 5:off 6:off
httpd  0:off 1:off 2:off 3:off 4:off 5:off 6:off
named  0:off 1:off 2:off 3:off 4:off 5:off 6:off
lpd    0:off 1:off 2:on  3:on  4:on  5:on  6:off
nfs    0:off 1:off 2:off 3:off 4:off 5:off 6:off
crond  0:off 1:off 2:on  3:on  4:on  5:on  6:off
xinetd 0:off 1:off 2:off 3:on  4:on  5:on  6:off
xinetd based services:
time:       off
finger:     off
pop3s:      off
swat:       on

Starting and Stopping Services with chkconfig

You use the

on option to have a service started at specified runlevels, and the

off option to disable it. You can specify the runlevel to affect with the

--level option. If no level is specified,

chkconfig will use any

chkconfig default information in a service's

init.d startup script. Red Hat installs its services with

chkconfig default information already entered (if this is missing,

chkconfig will use runlevels 3, 4, and 5). The following example has the Web server (

httpd ) started at runlevel 5:

chkconfig --level 5 httpd on

The

off option configures a service to shut down if the system enters a specified runlevel. The next example shuts down the Web server if runlevel 3 is entered. If the service is not running, it remains shut down:

chkconfig --level 3 httpd off

The

reset option restores a service to its

chkconfig default options as specified in the service's

init.d startup script:

chkconfig httpd reset

To see just the startup information for a service, you use just the service name with the

--list option:

chkconfig --list httpd
httpd   0:off  1:off 2:off 3:on 4:off 5:on 6:off

Enabling and Disabling xinetd Services with chkconfig

Unlike redhat-config-services,

chkconfig can also enable or disable

xinetd services. Simply enter the

xinetd service with either an

on or

off option. The service will be started up or shut down, and the disable line in its

xinetd configuration script in the

/etc/xinetd.d directory will be edited accordingly. For example, to start

swat , the Samba configuration server, which runs on

xinetd , you simply enter:

chkconfig swat on
chkconfig --list swat
swat          on

The

swat configuration file for

xinetd ,

/etc/xinetd.d/swat , will have its disable line edited to no, as shown here:

disable=no

If you want to shut down the swat server, you can use the

off option. This will change the disable line in

/etc/xinetd.d/swat to read "disable=yes".

chkconfig swat off

The same procedure works for other

xinetd services such as the POP3 server and

finger .

Removing and Adding Services with chkconfig

If you want a service removed entirely from the entire startup and shutdown process in all runlevels, you can use the

--del option. This removes all startup and shutdown links in all the runlevel directories.

chkconfig --del httpd

You can also add services to

chkconfig management with the

--add option.

chkconfig will create startup links for the new service in the appropriate startup directories,

/etc/rc.d/rc

n

.d . If you have previously removed all links for a service, you can restore them with the

add option.

chkconfig --add httpd

Configuring xinetd Services for Use by chkconfig

Default runlevel information should be placed in the startup scripts that are to be managed by

chkconfig . Red Hat has already placed this information in the startup scripts for the services that are installed with its distribution. You can edit these scripts to change the default information if you wish. This information is entered as a line beginning with a

# sign and followed by the

chkconfig keyword and a colon. Then you list the default runlevels that the service should start up on, along with the start and stop priorities. The following entry lists runlevels 3 and 5 with a start priority of 85 and a stop of 15. See the section on Service Script Tags for more information:

# chkconfig: 35 85 15

So when a user turns on the

httpd service with no level option specified,

chkconfig will start up

httpd at runlevels 3 and 5.

chkconfig httpd on

How chkconfig Works

The

chkconfig tool works by creating startup and shutdown links in the appropriate runlevel directories in the

/etc/rc.d directory. For example, when

chkconfig adds the

httpd service at runlevel 5, it creates a link in the

/etc/rc.d/rc5.d directory to the startup script

httpd in the

/etc/rc.d/init.d directory. When it turns off the Web service from runlevel 3, it creates a shutdown link in the

/etc/rc.d/rc3.d directory to use the script

httpd in the

/etc/rc.d/initd directory to make sure the Web service is not started. In the following example, the user turns on the Web service (

httpd ) on runlevel 3, creating the startup link in

rc5.d ,

S85httpd , and then turns off the Web service on runlevel 3, creating a shutdown link in

rc3.d ,

K15httpd .

chkconfig -level 5 httpd on
ls /etc/rc.d/rc5.d/*httpd
/etc/rc.d/rc5.d/S85httpd
chkconfig -level 3 httpd off
ls /etc/rc.d/rc3.d/*httpd
/etc/rc.d/rc3.d/K15httpd