Disable Lid Suspend

Most laptops suspend when the lid is down and in order to solve this problem for a laptop server, it's better to fix this problem on the systemd level.

Edit /etc/systemd/logind.conf

sudo nano /etc/systemd/logind.conf

Set HandleLidSwitch=ignore

Restart systemd-logind :

sudo systemctl restart systemd-logind

xfce4-power-manager (Crunchbang)

Sometimes, due to the intervention of graphical utilities, you will need to do a second step: open Power Manager and modify the settings.