Introducing Shrubbery: a cheap BMC-equivalent for Linux Machines

I run a little server on my apartment network for small services (an IRC bouncer, some screens, SSH and MD-Raid).  However, I’m not always at the machine when I’m working on it.  I have, in the past, been lucky and not taken it totally offline when doing upgrades remotely.  Until this week.

Having now accidentally removed myself from all the services I usually use, I’m frustrated.  In my work life, I often use servers which have Baseboard Management Controllers (BMC).  The BMC is a device which sits on the motherboard of a machine and is able to do many things - report on sensors, whether the machine is powered or not, change the power status and connect a serial console.  A properly configured BMC makes it possible to do pretty much anything to a machine remotely, save for adjusting the hardware.  In my current conundrum (a kernel which won’t boot), this would be immensely helpful - I could use the serial console to select an older, working kernel and then fix …