Login shell and non-login shell

  What is a login shell: A login shell can be used by users to log in, such as /bin/bash,/bin/sh,/bin/csh... Generally, the default user shell of Linux is bash, that is, you can log in Go in and write commands.
    Non-login shell: The classic /bin/nologin is a non-login shell, which means that if a user defaults to it, the user cannot use linux even if he logs in to linux.
    The shell is the medium for users to communicate with the computer. The login shell ensures the communication between the user and the computer. The non-login shell cannot allow the computer to communicate with the user.
    The default login shell for a user is recorded in the /etc/passwd file.
    The non-login shell has its specific purpose, such as an ftp server built with linux, and multiple users are created, then the default shell of these users can be changed to nologin, so that these users are users on linux but Can not log into the linux host, can only enter the ftp server, which also ensures security!