#!/bin/bash
# 向一個臨時文件中寫入配置的內容，兩種形式service和systemctl
sudo cat >/tmp/mysql-exporter-systemctl<<EOF
[Unit]
Description=Mysql Exporter
After=network.target
[Service]
ExecStart= ...
[Install]
WantedBy=default.target
EOF
sudo cat >/tmp/mysql-exporter-service<<EOF
#!/bin/bash
case "\$1" in
start)
...
echo \$!>/var/run/[servicename].pid
;;
stop)
sudo kill \`cat /var/run/[servicename].pid\`
sudo rm -f /var/run/[servicename].pid
;;
restart)
\$0 stop
\$0 start
;;
status)
if [ -e /var/run/[servicename].pid ]; then
echo [servicename] is running, pid=\`cat /var/run/[servicename].pid\`
else
echo [servicename] is NOT running
exit 1
fi
;;
*)
echo "Usage: \$0 {start|stop|status|restart}"
esac
exit 0
EOF
function service_conf(){
# 判斷使用那種形式的配置內容
if [ -x /usr/bin/systemctl ]; then
sudo mv /tmp/mysql-exporter-systemctl /usr/lib/systemd/system/[servicename].service
sudo chmod 754 /usr/lib/systemd/system/[servicename].service
sudo systemctl daemon-reload
sudo systemctl enable [servicename].service
elif [ -x /bin/systemctl ]; then
sudo mv /tmp/mysql-exporter-systemctl /lib/systemd/system/[servicename].service
sudo chmod 754 /lib/systemd/system/[servicename].service
sudo systemctl daemon-reload
sudo systemctl enable [servicename].service
else
sudo mv /tmp/mysql-exporter-service /etc/init.d/[servicename]
sudo chmod 755 /etc/init.d/[servicename]
fi
}
service_conf這個腳本使用於多個操作系統
Systemd 默認從目錄/etc/systemd/system/讀取配置文件。但是，裏面存放的大部分文件都是符號鏈接，指向目錄/usr/lib/systemd/system/，真正的配置文件存放在那個目錄。
systemctl enable命令用於在上面兩個目錄之間，建立符號鏈接關係。
$ sudo systemctl enable [email protected]
# 等同於
$ sudo ln -s '/usr/lib/systemd/system/[email protected]' '/etc/systemd/system/multi-user.target.wants/[email protected]'
如果配置文件裏面設置了開機啓動，systemctl enable命令相當於激活開機啓動。
與之對應的，systemctl disable命令用於在兩個目錄之間，撤銷符號鏈接關係，相當於撤銷開機啓動。
