PC engines APU2, Debian Stretch and watchdog

I bought a very cool APU2 from PC engines.

Installing Debian Stretch

Very easy:

• Download netinst image from https://www.debian.org/distrib/
• Download https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/SHA256SUMS and https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/SHA256SUMS.sign
• Verify signature: gpg2 --verify SHA256SUMS.sign SHA256SUMS
• Copy to USB stick: dd if=debian-9.0.0-amd64-netinst.iso of=/dev/sdX bs=1M
• Plug USB stick in APU
• Boot on USB stick
• In Debian installer, scroll down, until you get Display help screens; type 'menu' at boot prompt to return to this menu" press "enter".
• Press F6
• Type install console=ttyS0,115200n8
• Install Debian

Watchdog tricks

Once the APU crashed for some reason while I was away, which is very annoying as it is my main router. Thankfully, the APU2 has a hardware watchdog. Unfortunately, it’s a bit buggy so we need to blacklist the i2c-piix4 module and load spi5100_tco ASAP.

So, do the following:

# apt install watchdog
# vim /etc/watchdog.conf # uncomment watchdog-device
# echo blacklist i2c_piix4 > /etc/modprobe.d/blacklist_piix.conf
# echo spi5100_tco >> /etc/initramfs-tools/modules
# update-initramfs -k all -u 

Adding spi5100_tco seems to be necessary to have the module reliably find the MMIO.

Enjoy.