軟件安裝成服務過程詳解：
service httpd restart
由三部分組成service(服務)、httpd（程序名）、restart（相關命令）少一不可
service: 是系統已經定義可的。無需更改。默認會查找/etc/init.d/*
httpd: 程序名這個是已經確定的。
restart: 相關命令，如start 這個是控制程序走向。
那麼非常明確的一個服務需要的流程:
1、程序是可執行程序
2、位置需放在/etc/init.d/目錄下
3、相關命令，這個由程序本身決定（有沒有指定）。
3.1 如果是已經有相關命令的，那麼文件直接拷貝到/etc/init.d目錄下，並給矛可執行權限。
3.2 如果是沒有定義，那我們需要寫一個腳本。並定義好相關命令。
一、看一個sshd實例，來幫助我們了解整體過程。
# vim /etc/init.d/sshd
----------sshd start------------------
#!/bin/bash
#
# Init file for OpenSSH server daemon
#
# chkconfig: 2345 55 25
# description: OpenSSH server daemon
#
# processname: sshd
# config: /etc/ssh/ssh_host_key
# config: /etc/ssh/ssh_host_key.pub
# config: /etc/ssh/ssh_random_seed
# config: /etc/ssh/sshd_config
# pidfile: /var/run/sshd.pid
# source function library
. /etc/rc.d/init.d/functions
# pull in sysconfig settings
[ -f /etc/sysconfig/sshd ] && . /etc/sysconfig/sshd
RETVAL=0
prog="sshd"
# Some functions to make the below more readable
KEYGEN=/usr/bin/ssh-keygen
SSHD=/usr/sbin/sshd
RSA1_KEY=/etc/ssh/ssh_host_key
RSA_KEY=/etc/ssh/ssh_host_rsa_key
DSA_KEY=/etc/ssh/ssh_host_dsa_key
PID_FILE=/var/run/sshd.pid
runlevel=$(set -- $(runlevel); eval "echo \$$#" )
do_rsa1_keygen() {
if [ ! -s $RSA1_KEY ]; then
echo -n $"Generating SSH1 RSA host key: "
if $KEYGEN -q -t rsa1 -f $RSA1_KEY -C '' -N '' >&/dev/null; then
chmod 600 $RSA1_KEY
chmod 644 $RSA1_KEY.pub
if [ -x /sbin/restorecon ]; then
/sbin/restorecon $RSA1_KEY.pub
fi
success $"RSA1 key generation"
echo
else
failure $"RSA1 key generation"
echo
exit 1
fi
fi
}
do_rsa_keygen() {
if [ ! -s $RSA_KEY ]; then
echo -n $"Generating SSH2 RSA host key: "
if $KEYGEN -q -t rsa -f $RSA_KEY -C '' -N '' >&/dev/null; then
chmod 600 $RSA_KEY
chmod 644 $RSA_KEY.pub
if [ -x /sbin/restorecon ]; then
/sbin/restorecon $RSA_KEY.pub
fi
success $"RSA key generation"
echo
else
failure $"RSA key generation"
echo
exit 1
fi
fi
}
do_dsa_keygen() {
if [ ! -s $DSA_KEY ]; then
echo -n $"Generating SSH2 DSA host key: "
if $KEYGEN -q -t dsa -f $DSA_KEY -C '' -N '' >&/dev/null; then
chmod 600 $DSA_KEY
chmod 644 $DSA_KEY.pub
if [ -x /sbin/restorecon ]; then
/sbin/restorecon $DSA_KEY.pub
fi
success $"DSA key generation"
echo
else
failure $"DSA key generation"
echo
exit 1
fi
fi
}
do_restart_sanity_check()
{
$SSHD -t
RETVAL=$?
if [ ! "$RETVAL" = 0 ]; then
failure $"Configuration file or keys are invalid"
echo
fi
}
start()
{
# Create keys if necessary
do_rsa1_keygen
do_rsa_keygen
do_dsa_keygen
cp -af /etc/localtime /var/empty/sshd/etc
echo -n $"Starting $prog: "
$SSHD $OPTIONS && success || failure
RETVAL=$?
[ "$RETVAL" = 0 ] && touch /var/lock/subsys/sshd
echo
}
stop()
{
echo -n $"Stopping $prog: "
if [ -n "`pidfileofproc $SSHD`" ] ; then
killproc $SSHD
else
failure $"Stopping $prog"
fi
RETVAL=$?
# if we are in halt or reboot runlevel kill all running sessions
# so the TCP connections are closed cleanly
if [ "x$runlevel" = x0 -o "x$runlevel" = x6 ] ; then
killall $prog 2>/dev/null
fi
[ "$RETVAL" = 0 ] && rm -f /var/lock/subsys/sshd
echo
}
reload()
{
echo -n $"Reloading $prog: "
if [ -n "`pidfileofproc $SSHD`" ] ; then
killproc $SSHD -HUP
else
failure $"Reloading $prog"
fi
RETVAL=$?
echo
}
case "$1" in
start)
start
;;
stop)
stop
;;
restart)
stop
start
;;
reload)
reload
;;
condrestart)
if [ -f /var/lock/subsys/sshd ] ; then
do_restart_sanity_check
if [ "$RETVAL" = 0 ] ; then
stop
# avoid race
sleep 3
start
fi
fi
;;
status)
status -p $PID_FILE openssh-daemon
RETVAL=$?
;;
*)
echo $"Usage: $0 {start|stop|restart|reload|condrestart|status}"
RETVAL=1
esac
exit $RETVAL
--------------sshd stop---------------------------
煮酒品茶：可以看出來，一些判斷語句和一些執行路徑。以即最下方的獲取相關命令並給予相關執行命令。瞧，一個服務的添加就這麼簡單。測試吧
過程如下：
[root@localhost test]# service test restart
test: unrecognized service
[root@localhost test]# cp test /etc/init.d/
[root@localhost test]# ll /etc/init.d/ |grep test
-rwxr-xr-x 1 root root 19 Apr 23 11:37 test
[root@localhost test]# service test restart
hello world
#vim /etc/init.d/test
-------------------test start---------------
case "$1" in
start)
echo -n "Starting test: "
~/test/test
echo -n "start is OK"
;;
stop)
echo -n "Shutting stop test: "
killall test
echo -n "stop is OK"
;;
esac
exit
-------------stop-------------------
[root@localhost test]# service test start
Starting test: hello world
start is OK[root@localhost test]# service test stop
Shutting stop test: test: no process killed
很簡單的的可以理解，先是放到service能找的著的地方，然後再給它判斷命令如果是start就寫文件正在啟動test中，啟動完後給一個啟動ok的。同理結束直接kill掉他的進程就好了。其它的自由發揮比如：reload、restart等。
