Logins from terminals

Logins from terminals (via serial lines) and the console (when not running X) are provided by the getty  program. init  starts a separate instance of getty  for each terminal for which logins are to be allowed. getty  reads the username and runs the login  program, which reads the password. If the username and password are correct, login  runs the shell. When the shell terminates, i.e., the user logs out, or when login  terminated because the username and password didn't match, init  notices this and starts a new instance of getty . The kernel has no notion of logins, this is all handled by the system programs.