使用 linux 时经常用到 ` service MySQL restart ` 等命令, 方便进行服务的操作, 具体的服务是怎么写的呢,通过以下示例将了解以下内容:

1. 如何写一个简单的服务
2. 服务异常关闭时能自动开启配置

简单的示例

nano /lib/systemd/system/xx.service

[Unit]
Description=Check GPU INFO by chenwei   # 服务描述
Wants=network-online.target             # 服务依赖于网络
After=network-online.target

[Service]
Type=simple
ExecStart=/root/shell/agent/chkgpu      # 服务开启时执行脚本
ExecReload=/bin/kill -HUP $MAINPID      # 服务重新加载时执行脚本
RestartSec=5s                           # 自动启动间隔时间
Restart=on-failure                      # 在什么情况下会自动重启

[Install]
WantedBy=multi-user.target  

[Unit]
Description=Advanced key-value store
After=network.target

[Service]
Type=forking
ExecStart=/usr/local/redis/bin/redis-server /usr/local/redis/etc/redis.conf
ExecStop=/bin/kill -s TERM $MAINPID
PIDFile=/var/run/redis_6379.pid
Restart=always
RestartSec=5s
Restart=on-failure


[Install]
WantedBy=multi-user.target
Alias=redis.service

Nginx 示例

[Unit]
Description=A high performance web server and a reverse proxy server
After=network.target

[Service]
Type=forking
PIDFile=/var/run/nginx.pid
#ExecStartPre=/usr/local/nginx/sbin/nginx 
ExecStart=/usr/sbin/nginx 
ExecReload=/usr/sbin/nginx -s reload
ExecStop=-/sbin/start-stop-daemon --quiet --stop --retry QUIT/5 --pidfile /run/nginx.pid
TimeoutStopSec=5
KillMode=mixed

[Install]
WantedBy=multi-user.target

常用命令

systemctl enable --now nginx.service  # 立刻开启并开机启动

systemctl daemon-reload #重新加载

systemctl enable nginx.service #开机时启动
systemctl disable nginx.service #开机时禁用
systemctl list-unit-files|grep enabled #已启动服务列表
systemctl --failed  #启动失败服务列表
 

sudo update-rc.d nginx defaults #开机时启动

wssh

file=/lib/systemd/system/myssh.service mv $file $file.bak cat «EOF »$file

[Unit] Description=Web SSH server by chenwei. pip install webssh Wants=network-online.target
After=network-online.target

[Service] Type=simple ExecStart=wssh ExecReload=/bin/kill -HUP $MAINPID
RestartSec=5s
Restart=on-failure

[Install] WantedBy=multi-user.target

EOF cat $file

issh

file=/usr/bin/issh
mv $file $file.bak
cat <<EOF >>$file
#!/bin/bash
wssh
autossh -M 10111 -NR 0.0.0.0:11111:localhost:22 pc@1.10sh.cn


EOF
cat $file

chmod +x  $file

file=/lib/systemd/system/issh.service
mv $file $file.bak

cat <<EOF >>$file
 
[Unit]
Description=autossh shell to connect to my server by chenwei.  #sudo apt  install autossh

Wants=network-online.target
After=network-online.target

[Service]
Type=simple
ExecStart=/usr/bin/issh
ExecReload=/bin/kill -HUP
RestartSec=5s
Restart=on-failure

[Install]
WantedBy=multi-user.target


EOF
cat $file


systemctl enable --now issh.service

systemctl status issh.service

pweb

使用Python 启动一个简单的 http 文件服务

sudo -i


file=/home/pweb.sh
mv $file $file.bak
cat <<EOF >>$file


#!/bin/bash
python3 -m http.server

EOF
cat $file

chmod +x  $file

file=/lib/systemd/system/pweb.service
mv $file $file.bak
cat <<EOF >>$file

 
[Unit]
Description=Simple python pweb by chenwei.

Wants=network-online.target
After=network-online.target

[Service]
Type=simple
ExecStart=/home/pweb.sh
ExecReload=/bin/kill -HUP
RestartSec=5s
Restart=on-failure

[Install]
WantedBy=multi-user.target


EOF
cat $file

systemctl enable --now pweb.service

systemctl status pweb.service