Getty is the program that enables you to log in through a serial device such as a virtual terminal, a text terminal, or a modem. It displays the login prompt. Once you enter your username, getty hands this over to
login which asks for a password, checks it out and gives you a shell.
There are many getty's available. Some distributions, including Red Hat use
a very small one called
mingetty that only works with virtual terminals.
login program is part of the util-linux package, which also
contains a getty called
agetty, which works fine. This package also
more (the program) and more (ie more programs).
The message that comes on the top of your screen with your login prompt comes
/etc/issue. Gettys are usually started in
Login checks user details in
/etc/passwd, and if you have password
/etc/passwd by hand. Passwords can be set to null, and
changed with the program
passwd once you log on. See the man page for
this file Use
man 5 passwd to get the man page for the file rather
than the man page for the program.