Heh, most FreeBSD information works directly on Illumos as well, they have the same root system. The main difference in Illumos is that jails are baked into the kernel, into the very process struct itself, so everything is running in a ‘jail’, including the original login in the root jail. 
That design fixes issues that FreeBSD’s jails have, like non-segmented network, poor control of CPU and RAM usage, etc…
