This is the UNIX operating system that the computer in TRON legacy is running, it appears to be an operating system that is created by Sun Microsystems, like Solaris.
The name of this operating system which is a play on the name of the Solaris UNIX operating system. The user flynn is trying to login as root using the login(1) command, but I do not know why he does not try to use su(1) instead. There is a good posting here [9gag.com] where they are looking at this scene. I think he used an account that did not have a password, but every time you create a new account, it always asks you for a password to give to the newly created user, so this is unlikely. The user he logged in with must have had root privileges therefore he gained root access when he logged in. But the screenshot does not show the system asking him for a password as any UNIX system would after you typed the username and pressed ENTER. There was a scene where a computer expert was using kill -9 to kill a rogue process and that is correct, but the login thing is a bit strange.
Anyway it is good to see some cool UNIX commands in movies, but they need to do more research on how the login actually works on UNIX when you want to log in. But in this screenshot the computer expert is using the ps command to find the process id of the offending process and kill -9 to actually kill the process for good. This is good cinema, even though I think they need to learn a little more about UNIX systems, this is a good start.