脚本可单独执行，在 .service 文件中使用就报错 #
背景 #
想要给树莓派添加个服务，每次开机后把 ip 发送到指定邮箱。结果配置好了后总是启动不起来，查看日志发现没有权限 Failed to execute command: Permission denied
-- Unit send_ip.service has begun starting up.
Sep 14 16:33:01 bogon systemd[11178]: send_ip.service: Failed to execute command: Permission denied
Sep 14 16:33:01 bogon systemd[11178]: send_ip.service: Failed at step EXEC spawning /usr/bin/script/send_ip.sh: Permission denied
-- Subject: Process /usr/bin/script/send_ip.sh could not be executed
-- Defined-By: systemd
-- Support: https://access.redhat.com/support
--
-- The process /usr/bin/script/send_ip.sh could not be executed and failed.
--
-- The error number returned by this process is 13.
Sep 14 16:33:01 bogon systemd[1]: send_ip.service: Control process exited, code=exited status=203
Sep 14 16:33:01 bogon systemd[1]: send_ip.service: Failed with result 'exit-code'.
Sep 14 16:33:01 bogon systemd[1]: Failed to start 开机后向管理员发送本机的ip.
-- Subject: Unit send_ip.service has failed
-- Defined-By: systemd
-- Support: https://access.redhat.com/support
--
-- Unit send_ip.service has failed.
已确认脚本确实是正确的，service 文件如下
[Unit]
Description=开机后向管理员发送本机的ip
After=network.target
[Service]
Type=forking
User=root
ExecStart=/usr/bin/script/send_ip.sh
PrivateTmp=true
[Install]
WantedBy=multi-user.target
查了下 code=exited status=203 表示
systemctl 执行脚本时需要知道脚本的解释器，可脚本前面明明有写 #!/bin/bash
原因 #
203 的错误提示没有错，确实是系统不知道脚本的解释，只是这里不应该是在脚本开头加 #!/bin/bash，而是在 ExecStart 里声明使用的解释器，将 ExecStart=/usr/bin/script/send_ip.sh 修改为 ExecStart=/bin/bash /usr/bin/script/send_ip.sh
修改后的 service 文件应该如下
[Unit]
Description=开机后向管理员发送本机的ip
After=network.target
[Service]
Type=forking
User=root
ExecStart=/bin/bash /usr/bin/script/send_ip.sh
PrivateTmp=true
[Install]
WantedBy=multi-user.target