Linux之系统服务----自己创建服务

前几天比较忙，今天才闲下来，接着上次的内容讲，今天主要给大家讲讲service类型的配置文件，说的简单一些就是如何自己创建一个自己想要的服务。
一、了解service的参数信息
要想自己创建一个服务可不是一蹴而就的，最好的办法就是想去学习一下系统中已有的服务是什么样的，是以什么方式运行的，只有知己知彼才能百战不殆。先来看看sshd这个服务。

然后呢分析一下其中的内容，首先【UNIT】代表的是下面一段内容是对该UNIT本身的说明介绍，我这里的系统中关于这段的介绍共有四点 ，实际上是有很多的，我在网上找到了关于这个参数的简介：
接下来再了解一下【service】中有哪些参数


最后咱们要说的就是【install】install部分

二、创建自己的服务
上面已经学习了一些service类型的配置文件的内容，然后我们创建一个可以备份自己系统的服务来耍耍，哈哈哈
在／usr/lib/systemd/system下创建nginx.service文件内容如下（看应用需求也可以在 ／usr/lib/systemd/usr下创建）：
输入以下命令：
1)创建nginx脚本

#!/bin/sh

### BEGIN INIT INFO
# Provides:   nginx
# Required-Start:    $local_fs $remote_fs $network $syslog $named
# Required-Stop:     $local_fs $remote_fs $network $syslog $named
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: starts the nginx web server
# Description:       starts nginx using start-stop-daemon
### END INIT INFO

PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
DAEMON=/usr/sbin/nginx
NAME=nginx
DESC=nginx

# Include nginx defaults if available
if [ -r /etc/default/nginx ]; then
    . /etc/default/nginx
fi

test -x $DAEMON || exit 0

. /lib/init/vars.sh
. /lib/lsb/init-functions

# Try to extract nginx pidfile
PID=$(cat /etc/nginx/nginx.conf | grep -Ev '^\s*#' | awk 'BEGIN {
     
      RS="[;{}]" } {
     
      if ($1 == "pid") print $2 }' | head -n1)
if [ -z "$PID" ]
then
    PID=/run/nginx.pid
fi

# Check if the ULIMIT is set in /etc/default/nginx
if [ -n "$ULIMIT" ]; then
    # Set the ulimits
    ulimit $ULIMIT
fi

#
# Function that starts the daemon/service
#
do_start()
{
    # Return
    #   0 if daemon has been started
    #   1 if daemon was already running
    #   2 if daemon could not be started
    start-stop-daemon --start --quiet --pidfile $PID --exec $DAEMON --test > /dev/null \
        || return 1
    start-stop-daemon --start --quiet --pidfile $PID --exec $DAEMON -- \
        $DAEMON_OPTS 2>/dev/null \
        || return 2
}

test_nginx_config() {
    $DAEMON -t $DAEMON_OPTS >/dev/null 2>&1
}

#
# Function that stops the daemon/service
#
do_stop()
{
    # Return
    #   0 if daemon has been stopped
    #   1 if daemon was already stopped
    #   2 if daemon could not be stopped
    #   other if a failure occurred
    start-stop-daemon --stop --quiet --retry=TERM/30/KILL/5 --pidfile $PID --name $NAME
    RETVAL="$?"

    sleep 1
    return "$RETVAL"
}

#
# Function that sends a SIGHUP to the daemon/service
#
do_reload() {
    start-stop-daemon --stop --signal HUP --quiet --pidfile $PID --name $NAME
    return 0
}

#
# Rotate log files
#
do_rotate() {
    start-stop-daemon --stop --signal USR1 --quiet --pidfile $PID --name $NAME
    return 0
}

#
# Online upgrade nginx executable
#
# "Upgrading Executable on the Fly"
# http://nginx.org/en/docs/control.html
#
do_upgrade() {
    # Return
    #   0 if nginx has been successfully upgraded
    #   1 if nginx is not running
    #   2 if the pid files were not created on time
    #   3 if the old master could not be killed
    if start-stop-daemon --stop --signal USR2 --quiet --pidfile $PID --name $NAME; then
        # Wait for both old and new master to write their pid file
        while [ ! -s "${PID}.oldbin" ] || [ ! -s "${PID}" ]; do
            cnt=`expr $cnt + 1`
            if [ $cnt -gt 10 ]; then
                return 2
            fi
            sleep 1
        done
        # Everything is ready, gracefully stop the old master
        if start-stop-daemon --stop --signal QUIT --quiet --pidfile "${PID}.oldbin" --name $NAME; then
            return 0
        else
            return 3
        fi
    else
        return 1
    fi
}

case "$1" in
    start)
        [ "$VERBOSE" != no ] && log_daemon_msg "Starting $DESC" "$NAME"
        do_start
        case "$?" in
            0|1) [ "$VERBOSE" != no ] && log_end_msg 0 ;;
            2) [ "$VERBOSE" != no ] && log_end_msg 1 ;;
        esac
        ;;
    stop)
        [ "$VERBOSE" != no ] && log_daemon_msg "Stopping $DESC" "$NAME"
        do_stop
        case "$?" in
            0|1) [ "$VERBOSE" != no ] && log_end_msg 0 ;;
            2) [ "$VERBOSE" != no ] && log_end_msg 1 ;;
        esac
        ;;
    restart)
        log_daemon_msg "Restarting $DESC" "$NAME"

        # Check configuration before stopping nginx
        if ! test_nginx_config; then
            log_end_msg 1 # Configuration error
            exit 0
        fi

        do_stop
        case "$?" in
            0|1)
                do_start
                case "$?" in
                    0) log_end_msg 0 ;;
                    1) log_end_msg 1 ;; # Old process is still running
                    *) log_end_msg 1 ;; # Failed to start
                esac
                ;;
            *)
                # Failed to stop
                log_end_msg 1
                ;;
        esac
        ;;
    reload|force-reload)
        log_daemon_msg "Reloading $DESC configuration" "$NAME"

        # Check configuration before reload nginx
        #
        # This is not entirely correct since the on-disk nginx binary
        # may differ from the in-memory one, but that's not common.
        # We prefer to check the configuration and return an error
        # to the administrator.
        if ! test_nginx_config; then
            log_end_msg 1 # Configuration error
            exit 0
        fi

        do_reload
        log_end_msg $?
        ;;
    configtest|testconfig)
        log_daemon_msg "Testing $DESC configuration"
        test_nginx_config
        log_end_msg $?
        ;;
    status)
        status_of_proc -p $PID "$DAEMON" "$NAME" && exit 0 || exit $?
        ;;
    upgrade)
        log_daemon_msg "Upgrading binary" "$NAME"
        do_upgrade
        log_end_msg 0
        ;;
    rotate)
        log_daemon_msg "Re-opening $DESC log files" "$NAME"
        do_rotate
        log_end_msg $?
        ;;
    *)
        echo "Usage: $NAME {start|stop|restart|reload|force-reload|status|configtest|rotate|upgrade}" >&2
        exit 3
        ;;
esac

**注意：**创建好脚本之后要记得设置脚本的权限为可执行。。。
2)创建nginx服务

[Unit]
Description=nginx - high performance web server
Documentation=http://nginx.org/en/docs/
After=network.target remote-fs.target nss-lookup.target
  
[Service]
Type=forking
PIDFile=/run/nginx.pid
ExecStartPre=/usr/sbin/nginx -t -c /etc/nginx/nginx.conf
ExecStart=/usr/sbin/nginx -c /etc/nginx/nginx.conf
ExecReload=/bin/kill -s HUP $MAINPID
ExecStop=/bin/kill -s QUIT $MAINPID
PrivateTmp=true
  
[Install]
WantedBy=multi-user.target

关于上述命令，我个人觉得有些多，最好还是找一个其他的服务复制过来，进行修改更快（我比较懒），每一个.target实际上是链接到我们单位文件的集合,当我们执行：
$ sudo systemctl enable nginx.service
就会在/etc/systemd/system/multi-user.target.wants/目录下新建一个/usr/lib/systemd/system/nginx.service 文件的链接。

3)操作service：

#启动服务
$ sudo systemctl start nginx.service
 
#查看日志
$ sudo journalctl -f -u nginx.service
-- Logs begin at 四 2015-06-25 17:32:20 CST. --
6月 25 10:28:24 Leco.lan systemd[1]: Starting nginx - high performance web server...
6月 25 10:28:24 Leco.lan nginx[7976]: nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
6月 25 10:28:24 Leco.lan nginx[7976]: nginx: configuration file /etc/nginx/nginx.conf test is successful
6月 25 10:28:24 Leco.lan systemd[1]: Started nginx - high performance web server.
 
#重启
$ sudo systemctl restart nginx.service
 
#重载
$ sudo systemctl reload nginx.service
 
#停止
$ sudo systemctl stop nginx.service

今天关于系统服务的内容就暂且讲到这里。