What is Shell & Ways to Change a User’s Default Shell in Linux?

What is Shell & Ways to Change a User’s Default Shell in Linux?

In this article, we will describe how to change a user’s shell in Linux. The shell is a program that accepts and interprets commands; there are several shells such as bash, sh, ksh, zsh, fish and many other lesser known shells available on Linux.

Bash (/bin/bash) is a popular shell on most if not all Linux systems, and it’s normally the default shell for user accounts.

The bash shell

A command line is a text-based interface which can be used to input instructions to a computer system. The Linux   command line is provided by a program called the shell. Over the long history of UNIX - like systems, many shells have been developed. The default shell for users in Linux is the GNU Bourn e-Again Shell (bash). Bash is an improved version of one of the most successful shells used on UNIX-like systems, the Bourne Shell (sh).

There are several reasons for changing a user’s shell in Linux including the following:

§  To block or disable normal user logins in Linux using a nologin shell.

§  Use a shell wrapper script or program to login user commands before they are sent to a shell for execution. Here, you specify the shell wrapper as a user’s login shell.

§  To meet a user’s demands (wants to use a specific shell), especially those with administrative rights.

When creating user accounts with the useradd or adduser utilities, the --shell flag can be used to specify the name of a user’s login shell other than that specified in the respective configuration files.

A login shell can be accessed from a text based interface or via a SSH from remote Linux machine. However, if you login via a graphical user interface (GUI), you can access the shell from a terminal emulators like xterm, konsole and many more.

Let’s first list all available shells on your Linux system, type.

# cat /etc/shells

/bin/sh

/bin/bash

/sbin/nologin

/bin/tcsh              

/bin/csh

/bin/dash

Before you proceed any further, note that:

§  A user can change their own shell to any thing: which, however must be listed in the /etc/shells file.

§  Only root can run a shell not listed in /etc/shells file.

§  If an account has a restricted login shell, then only root can change that user’s shell.

Now let’s discuss three different ways to change Linux user shell.

How to check current Shell in Linux

# echo $$SHELL

 chsh command

chsh is a command line utility for changing a login shell with the -s or –shell option like this.

# chsh --shell /bin/sh tecmint

#exec bash {without restart execute shell in user mode}