Most of the Linux flavors use BASH as default shell. But as per requirements or interest people tend to use other shells. In our case, we saw server had CSH set as default SHELL.
Now, there is a utility called chsh is used for changing your default shell without requiring manual modifications in /etc/passwd
How to use chsh to change your default shell?
First of all look at available shells
cat /etc/shells
# /etc/shells: valid login shells /bin/csh /bin/sh /usr/bin/es /usr/bin/ksh /bin/ksh /usr/bin/rc /usr/bin/tcsh /bin/tcsh /usr/bin/esh /bin/dash /bin/bash /bin/rbash /usr/bin/screen