The power returns, but your server remains dead and dark. You are miles away, unable to press the physical power button.
You cannot achieve a reliable WoL setup with just any hardware. You need components that maintain a "standby" power state even when the computer is technically turned off. 1. The Right APC UPS
Your network switches, routers, and the device sending the Magic Packet must be plugged into the battery-protected outlets of the APC UPS. If your network switch loses power and reboots slowly, the Magic Packet will be lost in transit before the target computer can receive it. Alternative Strategy: "Restore on AC Power Loss" apc ups wake on lan best
In /etc/apcupsd/onbattery.sh , you can include logic:
: In APC PowerChute settings, ensure the option to turn off the UPS after a client shuts down is unchecked . The power returns, but your server remains dead and dark
| Problem | Cause | Best Fix | |---------|-------|----------| | Server won’t wake after UPS shutdown | NIC lost WoL config in S5 | Use Intel/Broadcom NIC; disable "Energy Efficient Ethernet" | | APC cuts USB power before WoL works | USB serial chip depowers NIC | Switch to NMC or serial (RS-232) connection | | Server wakes randomly | Broadcast WoL packets | Enable "Secure WoL" with password or directed packet only | | Dual PSU servers | Second PSU on different UPS | Connect both UPS to same output group or use single PSU for WoL |
By following the best practices outlined in this guide—including utilizing killpower , implementing startup delays, and considering a master/slave topology—you can stop manually rebooting servers and gain true peace of mind, knowing your network will automatically rise again when the lights come back on. You need components that maintain a "standby" power
To achieve the most reliable "wake" behavior after a power event, use these settings:
For Wake-on-LAN to function, the computer's motherboard must remain in a standby state (S5 power state) and the Network Interface Card (NIC) must receive a small amount of trickle power (+5VSB) from the power supply.
If you must use WoL (e.g., you want the server to stay off until you're ready), use a secondary device that stays on or boots faster than your server, such as a Raspberry Pi or a router like the UniFi Dream Machine
Your computer's motherboard must support states—specifically the S5 state (soft off). The power supply must also provide continuous standby voltage (+5VSB) to the motherboard while the system is off. This keeps the network port alive. 3. Network Interface Card (NIC)