## 开启自启动

### Tomcat 开机自启动
```shell
#1.新增脚本
cd /etc/init.d
vim tomcat
chmod +x tomcat
#2.配置为系统服务器
chkconfig --add tomcat
#3.启动服务
service tomcat start
```

脚本 /etc/init.d/tomcat 内容如下：

```shell
#!/bin/sh
# chkconfig: 2345 40 60
# description: Start Or Stop Tomcat
# author: liuchuanwei.ex     
# version: v1.01

EXEC=/app/tomcat/bin/startup.sh
DIR=/app/tomcat

PID=`ps --no-heading -C java -f --width 1000 | grep $DIR |awk '{print $2}'`
if [[ ! -x /proc/${PID} || -z $PID ]]; then
	PID=0
fi

case "$1" in
    start)
		if [ $PID -eq 0 ]; then
			sh $EXEC
		else
			echo "Tomcat is already running"
		fi
        ;;
    stop)
        if [ $PID -eq 0 ]; then
			echo "Tomcat is not running"
        else
			echo "Shutting down tomcat ($PID)"
            kill -9 $PID > /dev/null 2>&1
            RETVAL=$?
            if [ $RETVAL -eq 0 ]; then
                echo "Tomcat is stoped"
            fi
        fi
        ;;
   status)
        if [ $PID -eq 0 ]; then
            echo 'Tomcat is not running'
        else
            echo "Tomcat is running ($PID)"
        fi
        ;;
   restart|force-reload)
        ${0} stop
        ${0} start
        ;;
    *)
        echo "Please use start or stop as first argument"
        ;;
esac
```

### Redis 开机自启动
```shell
#1.复制脚本
cp /home/redis/utils/redis_init_script /etc/init.d/redis
#2.复制配置
mkdir /etc/redis
cp /home/redis/redis.conf /etc/redis/redis_6379.conf
cp /home/redis/sentinel.conf  /etc/redis/redis-sentinel_26379.conf

#3.修改脚本，在 `#!bin/sh` 下新增一行 `# chkconfig: 2345 10 90  `
vim /etc/init.d/redis
#4.新增系统服务
chkconfig --add redis
#5.启动服务
service redis start
```

脚本 /etc/init.d/redis 内容如下：

```shell
#!/bin/sh
# chkconfig: 2345 10 90
# description: Start Or Stop Redis Server
# author: liuchuanwei.ex     
# version: v1.01

#redis配置
REDISPORT=6379
EXEC=/home/redis/src/redis-server
CLIEXEC=/home/redis/src/redis-cli
PIDFILE=/var/run/redis_${REDISPORT}.pid
CONF="/etc/redis/redis_${REDISPORT}.conf"
REDISPASSWORD="i!E@22h98lpQ5"
#哨兵配置
SENTINEL_PORT=26379
SENTINEL_EXEC=/home/redis/src/redis-sentinel
SENTINEL_CONF="/etc/redis/redis-sentinel_${SENTINEL_PORT}.conf --sentinel"

case "$1" in
    start)
        if [ -f $PIDFILE ] then
            echo "$PIDFILE exists, process is already running or crashed"
        else
            echo "Starting Redis server..."
            #启动redis
            $EXEC $CONF
            #启动哨兵
            $EXEC $SENTINEL_CONF
        fi
        ;;
    stop)
        if [ ! -f $PIDFILE ] then
            echo "$PIDFILE does not exist, process is not running"
        else
            PID=$(cat $PIDFILE)
            echo "Stopping ..."
            #关闭redis
            $CLIEXEC -a $REDISPASSWORD -p $REDISPORT shutdown
            #关闭哨兵
            $SENTINEL_EXEC -p $SENTINEL_PORT shutdown 
            sleep 2
            while [ -x /proc/${PID} ]
            do 
                echo "Waiting for Redis to shutdown ..."
                sleep 1
            done
            echo "Redis stopped"
        fi
        ;;
   status)
        PID=$(cat $PIDFILE)
        if [ ! -x /proc/${PID} ] then
            echo 'Redis is not running'
        else
            echo "Redis is running ($PID)"
        fi
        ;;
   restart|force-reload)  
        ${0} stop  
        ${0} start  
        ;; 
    *)
        echo "Please use start or stop as first argument"
        ;;
esac
```

## 后台运行

**首先理解任务是如何中断的**

当我们关闭终端，shell默认会发送中断信号给该终端session关联的进程，从而导致进程跟随终端退出。

**两种中断信号：**

1）sigint：signal interrupt，ctrl+c会发送此信号，主动关闭程序

2）sighup: signal hang up，关闭终端，ssh掉线，关闭屏幕会发送此挂断信号。

几种后台运行任务的方法：

**1）&符号**

将&符号放在命令最后面，使启动的程序忽略sigint信号，此时执行ctrl+c不会关闭进程，但当断网或关闭终端时，仍会造成进程退出。

例：bash test.sh &

**2）nohup指令**

nohup（no hang up），指不挂断运行，使用nohup在后台执行任务，和用户终端没有关系，所以断开ssh也不影响运行，nohup捕获了sighup信号，并做了忽略处理，因此断开终端不会关闭进程，但使用ctrl+c可以关闭该进程，所以一般用nohup+&结合使用。

例：nohup command

**3）结合使用**

方法1
```shell
nohup command &>> log.out &
```

方法2
```shell
su - root -c "command &>> log.out &"
```

4）运行后补救措施

当我们已经在前台开启了一个任务，想让其在后台运行，但又不想中断后重新开启该怎么办呢？

①将作业挂起

ctrl+z

②查看作业号
```shell
jobs
```

③将挂起的作业在后台运行
```shell
bg jobid
```

如果想继续放在前台运行：`fg jobid`