If you're puzzled why you can't Telnet into your A/UX machine, nfs0 needs to be set to wait and net9 needs to be set to respawn in /etc/inittab, or incoming connections like Telnet and FTP don't (or, depending on what inetd you're using, connections may just sit there and inetd fails to spawn the daemon, sometimes for as long as a half an hour). This means you need to be running /etc/portmap as well as /etc/inetd; you can't run just inetd. You should probably also upgrade to jagubox inetd. You might be able to get around this by not using portmap services in /etc/servers but I haven't needed to try that.
If you are sitting at the "Welcome to A/UX" dialogue box (i.e., you aren't logged into the machine and you have autologin disabled), you have to select Special, Restart to properly unmount the file systems. Selecting Special, Shut Down bizarrely leaves them dirty (forcing a long and unnecessary fsck on the next boot), and running shutdown from a root console doesn't consistently work right either. So now I have it rigged to not autoboot from the Mac boot partition, I select Restart from A/UX when I'm done, and then when the machine comes back up in the Mac boot partition, the A/UX filesystem is clean and I just shut down the Mac partition without continuing through the boot. The downside is I have to press Cmd-B manually to start the boot when I do want to be in A/UX.
This machine runs A/UX with my custom partitioning, which I document in more detail elsewhere.
I do have to say that on my clock-chipped Quadra 800 (to 36MHz), A/UX is a real pleasure. If they had ported it to PowerPC natively I bet it could have really been something spectacular even though it was sort of a dog's breakfast under the hood (but in that respect no worse than the classic MacOS).