Within raspian (I would need to check for other OSs), 'adduser USER' starts a dialog (TUI) while 'useradd USER' does NOT.
Apparently, using adduser, once the dialog comes up, the full 'useradd' command is already executed. Even if you CTRL-C your user is there.
As in the new systems they create "personal" groups, to remove the newly created user you would need to:
- vi /etc/passwd
- vi /etc/group
- rm -rf /home/USER
I assume that because adduser "uses" useradd, the rest is metadata about the user.
So technically no changes in "skel", "file masks", or the like, i.e. your system defaults.
On the other side, because useradd does not bring up any TUI, it might be more useful in
To be honest I tested it only in rasbian, because that was the reason I stepped on the question.
I can imagine that other OSs might implement a different version of adduser.