I have a vague recollection of my 20 floppy of Slackware already having /etc/shadow. That would have been fall of 92 or winter 93, based on where I was living at the time.
I have a vague recollection of being given the choice on a 90s vintage distribution with some warning about security and password length if I did not use shadow passwords. At some point in the early 2000s we started authenticating regular users against AD but the shadow file was still there for root.
We had a couple of labs of sparcstations that just went away a couple of times a year because something bad would happen with all of the NFS mounted partitions and they'd have to turn the cluster on one box at a time to prevent thundering herd issues with NFS.
I think they may have been mounting parts of /etc as well. People get the idea that managing accounts for a cluster of boxes should be centralized. It's all fun and games until the network mount disappears.
