參考網址：https://helloworld.pixnet.net/blog/post/47874794-%E5%95%9F%E7%94%A8-ubuntu-20.04–etc-rc.local
ubuntu 20.04 預設重開機時無法啟用 /etc/rc.local
如果要重開機後執行的話，修改方式如下
1. 在檔案的最末端加入以下三行，存檔離開
sudo vi /lib/systemd/system/rc-local.service
[Install]
WantedBy=multi-user.target
Alias=rc-local.service
2. 建立 rc.local
sudo vi /etc/rc.local
#!/bin/sh -e
echo `date` >> /tmp/reboot.log
exit 0
3. 加入可執行權限
sudo chmod u+x /etc/rc.local
4. 設定開機啟動，並手動啟用測試
sudo systemctl enable rc-local
sudo systemctl start rc-local
5. 檢視是否已啟用
sudo systemctl status rc-local
● rc-local.service – /etc/rc.local Compatibility
Loaded: loaded (/lib/systemd/system/rc-local.service; enabled; vendor preset: enabled)
Drop-In: /usr/lib/systemd/system/rc-local.service.d
└─debian.conf
Active: active (exited) since Fri 2021-09-17 01:53:56 UTC; 3s ago
Docs: man:systemd-rc-local-generator(8)
Process: 989234 ExecStart=/etc/rc.local start (code=exited, status=0/SUCCESS)
Sep 17 01:53:56 example systemd[1]: Starting /etc/rc.local Compatibility…
Sep 17 01:53:56 example systemd[1]: Started /etc/rc.local Compatibility.
6. 建立連結
sudo ln -s /lib/systemd/system/rc-local.service /etc/systemd/system/rc-local.service
7. 重開機
sudo reboot