Re: ONU
Got dumped with OS/400 once when I was helping configure one (without knowing anything it) by someone who promptly went on holiday for the next 2 weeks leaving me as the "expert" after being given an introduction into it using the words "This is the login/password, I'm off on holiday now, bye".
Cupboard full of manuals and people asking me about x, y, z.
Once I got into the steep learning curve of logging in and then "now, what", actually came to like the command verb syntax. I reckon if you thought about what you wanted to do, you could work out the command 95% of the time without looking it up, and the command prompting was excellent.
Very weird operating system though.