Some weekend reading. I really enjoyed this one about lessons from 20 years of the L4 microkernel. (Before I read this I couldn't have told you anything about L4 vs Mach vs any other microkernel, but it was readable despite that. If I was writing super-low-level device firmware, this design sounds like something I'd appreciate. The way user processes "donate" memory to make room for kernel objects seems really clever.)
ssh+2FA to all your machines, anywhere, without opening firewall ports.