Most server software using RPM Red Hat packages will automatically install the startup scripts and create the needed links in the appropriate
rc
N
.d directories, where N is the runlevel number. Startup scripts, though, can be used for any program you may want run when your system starts up. To have such a program start automatically, you first create a startup script for it in the
/etc/rc.d/init.d directory, and then create symbolic links to that script in the
/etc/rc.d/rc3.d and
/etc/rc.d/rc5.d directories. A shutdown link (K) should also be placed in the
rc6.d directory used for runlevel 6 (reboot).
A simplified version of the startup script
httpd uses on Red Hat systems is shown in a later section. You can see the different options, listed in the
/etc/rc.d/init.d/httpd example, under the
case statement:
start ,
stop ,
status ,
restart , and
reload . If no option is provided (
* ),the script use syntax is displayed. The
httpd script first executes a script to define functions used in these startup scripts. The
daemon function with
httpd actually executes the
/usr/sbin/httpd server program.
echo -n "Starting httpd: " daemon httpd echo touch /var/lock/subsys/httpd
The
killproc function shuts down the daemon. The lock file and the process ID file (
httpd.pid ) are then deleted:
killproc httpd echo rm -f /var/lock/subsys/httpd rm -f /var/run/httpd.pid
The
daemon ,
killproc , and
status functions are shell scripts defined in the
function s script, also located in the
inet.d directory. The
functions script is executed at the beginning of each startup script to activate these functions. A list of these functions is provided in Table 20-4.
. /etc/rc.d/init.d/functions
|
Init Script Function
|
Description
|
|---|---|
|
daemon [+/-nicelevel] program [arguments] [&]
|
Starts a daemon, if it is not already running.
|
|
killproc program [signal]
|
Sends a signal to the program; by default it sends a SIGTERM , and if the process doesn't stop, it sends a SIGKILL . It will also remove any PID files, if it can.
|
|
pidofproc program
|
Used by another function, it determines the PID of a program.
|
|
status program
|
Displays status information.
|
The beginning of the startup script holds tags used to configure the server. These tags, which begin with an initial
# symbol, are used to provide runtime information about the service to your system. The tags are listed in Table 20-5, along with the startup functions. You enter a tag with a preceding
# symbol, the tag name with a colon, and then the tag arguments. For example, the
processname tag specifies the name of the program being executed, in this example
|
Init Script Tags
|
Description
|
|---|---|
|
# chkconfig: startlevellist startpriority endpriority
|
Required. Specifies the default start levels for this service as well as start and end priorities.
|
|
# description [ln]: description of service
|
Required. The description of the service, continued with \ characters. Use an initial # for any added lines. With the ln option, you can specify the language the description is written in.
|
|
# autoreload: true
|
Optional. If this line exists, the daemon checks its configuration files and reloads them automatically when they change.
|
|
# processname: program
|
Optional, multiple entries allowed. The name of the program or daemon started in the script.
|
|
# config: configuration-file
|
Optional, multiple entries allowed. Specifies a configuration file used by the server.
|
|
# pidfile: pid-file
|
Optional, multiple entries allowed. Specifies the PID file.
|
|
# probe: true
|
Optional, used in place of autoreload , processname , config , and pidfile entries to automatically probe and start the service.
|
# processname: httpd
If your script starts more than one daemon, you should have a
processname entry for each. For example, the Samba service starts up both the
smdb and
nmdb daemons.
# processname: nmdb
The end of the tag section is indicated by an empty line. After this line, any lines beginning with a
# are treated as comments. The
chkconfig line lists the default runlevels that the service should start up on, along with the start and stop priorities. The following entry lists runlevels 3, 4, and 5 with a start priority of 85 and a stop of 15:
# chkconfig: 345 85 15
For the description, you enter a short explanation of the service, using the \ symbol before a newline to use more than one line.
# description: Apache Web server
With
config tags, you specify the configuration files the server may use. In the case of the Apache Web server, there may be three configuration files:
# config: /etc/httpd/conf/access.conf # config: /etc/httpd/conf/httpd.conf # config: /etc/httpd/conf/srm.conf
The
pidfile entry indicates the file where the server's process ID is held.
As an example, a simplified version of the Web server startup script,
/etc.rc.d/init.d/httpd
, is shown here. Most scripts are much more complicated, particularly when determining any arguments or variables a server may need to specify when it starts up. This script has the same name as the Web server daemon,
#!/bin/sh
#
# Startup script for the Apache Web Server
#
# chkconfig: 35 85 15
# description: Apache is a World Wide Web server. # It is
used to serve HTML files and CGI.
# processname: httpd
# pidfile: /var/run/httpd.pid
# config: /etc/httpd/conf/access.conf
# config: /etc/httpd/conf/httpd.conf
# config: /etc/httpd/conf/srm.conf
# Source function library.
. /etc/rc.d/init.d/functions
# See how we were called.
case "$1" in
start)
echo -n "Starting httpd: "
daemon httpd
echo
touch /var/lock/subsys/httpd
;;
stop)
killproc httpd
echo
rm -f /var/lock/subsys/httpd
rm -f /var/run/httpd.pid
;;
status)
status httpd
;;
restart)
$0 stop
$0 start
;;
reload)
echo -n "Reloading httpd: "
killproc httpd -HUP
echo
;;
*)
echo "Usage: $0 {start|stop|restart}"
exit 1
esac
exit 0
The RPM packaged versions for an Internet server include the startup script for that server. Installing the RPM package installs the script in the
/etc/rc.d/init.d directory and creates its appropriate links in the runlevel directories, such as
/etc/rc.h/rc3.d . If you decide, instead, to create the server using its source code files, you can then manually install the startup script. If no startup script exists, you first make a copy of the
httpd script— renaming it—and then edit the copy to replace all references to
httpd with the name of the server daemon program. Then place the copy of the script in the
/etc/rc.d/init.d directory and make a symbolic link to it in the
/etc/rc.d/rc3.d directory. Or you could use redhat-config-services to create the link in the
/etc/rc.d/rc3.d directory. Select File | Refresh Services. When you start your system now, the new server is automatically started up, running concurrently and waiting for requests.