How To Change Shell To Bash in Linux / Unix

How do I switch from a ksh shell to bash on Linux or Unix system? How to change shells on Unix-like system?

A shell is nothing but a command that provides a text-only user interface (also known as “command line interface”) for Linux, MacOS, and Unix-like operating systems. Bash shell read commands such as ls, date and others typed into a terminal and then run them. That is the primary function of bash shell.

Tutorial details
Difficulty level	Easy
Root privileges	No
Requirements	Linux or Unix-like OS
Est. reading time	2 minutes

How do I find out the default shell for a user?

Type the following command to find out the default shell for a user named vivek using the grep command and /etc/passwd file:
$ grep vivek /etc/passwd
vivek:x:1005:1005:,,,:/home/vivek:/bin/zsh
OR
$ ps -p $$
PID TTY TIME CMD
14314 pts/9 00:00:00 zsh
OR
$ echo $0
zsh
All of the above output indicates that the shell is zsh for user named vivek in Linux operating system.

How do I see what shells are available on my system?

Type the cat command as follows:
$ cat /etc/shells

The /etc/shells is a text file that contains the full pathnames of valid login shells. This file is consulted by the chsh command and available to be queried by other programs. Hence, only use shell names and paths mentioned in this file.

How do I switch to a bash or different shell?

Type the name at the command line and then press the enter key. In this example, to change from any shell to the bash, type:
bash

How to change shells on a Linux or Unix-like systems?

You can change your default shell using the chsh (“change shell” ) command as follows. The syntax is:
chsh
chsh -s {shell-name-here}
chsh -s {shell-name-here} {user-name-here}
chsh -s /bin/bash
chsh -s /bin/bash vivek
You can find full path to your shell using the following command:
type -a bash
type -a zsh
type -a ksh
Please note that a normal user may only change the login shell for her own account. The superuser (root) may change the login shell for any account using the following syntax:
$ sudo chsh -s /bin/bash raj
OR use the su command instead of sudo command:
$ su -
# chsh -s /bin/bash monika

Summing up

The only restriction placed on the login shell is that the shell command name must be listed in /etc/shells file, unless the invoker is the superuser/root user, and then any value may be added. An account with a restricted login shell may not change her login shell. For this reason, placing /bin/rsh in /etc/shells is discouraged since accidentally changing to a restricted shell would prevent the user from ever changing her login shell back to its original value.

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