So my question is.....
Will OSX Server run on a desktop. Will it run on a single processor machine. If I buy a tower mac it should work on that right? Also most tower macs have 1 NIC port. Will any PCI nic work or does it have to be MAC? If so then where can I get MAC NIC's?
Yes. It will run on any G4+ Mac hardware. You can even install it on a Mini.
I'm not sure about the Nic. I would assume that any standard PCI NIC should work. Your best bet would be to throw an old 3c905 in and see if it detects.
And finally.....
Is there a linux distro out there that is similar to OSX in terms of administration at least?
No. Nothing even remotely close.
