在休眠前锁定(lightdm)

新建/lib/systemd/system/dmlock.service, 内容如下：

[Unit]
Description=DM Lock before sleep
Before=sleep.target

[Service]
Environment="XDG_SEAT_PATH=/org/freedesktop/DisplayManager/Seat0"
ExecStart=/usr/bin/dm-tool lock

[Install]
WantedBy=sleep.target

其中XDG_SEAT_PATH的值可以由命令 dm-tool list-seats 确定。

然后

sudo systemctl enable dmlock.service

也可以测试效果

sudo systemctl start dmlock.service