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## 20. My Mac won’t power back up by itself into Linux after the UPS shuts down. What can I do about this?

This is about the same situation as the ATX question above, only worse. Earlier Macs apparently supported a hack where you could cat some magic characters at `/dev/adb` to enable "server mode". This would instruct the system to reboot while unattended.

From Usenet post <6boftzxz51.fsf@ecc-office.sp.cs.cmu.edu>:

            # Send packet over the ADB bus to the PowerMac CUDA chip
            # telling it to reboot automatically when power is restored
            # after a power failure.

            cat /etc/local/autoboot.adb > /dev/adb

        # autoboot.adb contains these three bytes (in hex):  01 13 01

Later PowerPC Macs with a PMU and the appropriate kernel driver can achieve the same effect with the following command:

    echo server_mode=1 > /proc/pmu/options

The following pages have some slightly more kludgy answers which involve the use of `setpci`, and are highly model-specific:

- https://www.mythic-beasts.com/support/servers/colo/macminicolo_howto
- http://superuser.com/questions/212434/reboot-after-power-failure-for-mac-running-ubuntu
- http://ubuntuforums.org/showthread.php?t=1209576

Note: this question has been in the FAQ for several years now, and there’s still no clean answer. Let me guess: everyone who runs a server on Mac hardware has a team of trained monkeys, and feeds them by growing bananas in the tropical environment formed by waste heat from the equipment.

The rest of us are still waiting for the answer. Booting into the Mac OS to frob the "file server" panel is not an acceptable solution.

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