Timed out waiting for device dev-ttyS0.device.

1. 从模板创建一个service:

cp /usr/lib/systemd/system/serial-getty@.service /etc/systemd/system/serial-getty@ttyS0.service

2. 修改 /etc/systemd/system/serial-getty@ttyS0.service内容:
   修改ExecStart这一行

ExecStart=-/sbin/agetty -a root -8 -L 115200 ttyS0 vt100

3. 创建软链接:
   ln -s /etc/systemd/system/serial-getty@ttyS0.service /etc/systemd/system/getty.target.wants/

https://www.cnblogs.com/dream397/p/14122290.html