I am wondering whether is it possible to log in in a computer with users like
postgres as I do with my own user. Are some users "allowed to log in" while others not? Is there any difference between my own user and the ones created by programs like apache, postgres besides name? They got password?? As you may see I have lots of doubts, maybe you could recommend me some reading about this topic!
The question born when I was trying to create a new group and add new users to that group in Ubuntu 11.04 via the gnome GUI. I was able to create a new group "test" but the system only allowed me to add my user to that group and not the other users in the system like the ones that appear in /etc/passwd (I was running the Add Users/Group GUI with sudo privileges).