How can I make bash my login shell?

From: Bash FAQ
A7)  How can I make bash my login shell?

Some machines let you use `chsh' to change your login shell.  Other
systems use `passwd -s' or `passwd -e'.  If one of these works for
you, that's all you need.  Note that many systems require the full
pathname to a shell to appear in /etc/shells before you can make it
your login shell.  For this, you may need the assistance of your
friendly local system administrator.

If you cannot do this, you can still use bash as your login shell, but
you need to perform some tricks.  The basic idea is to add a command
to your login shell's startup file to replace your login shell with
bash.

For example, if your login shell is csh or tcsh, and you have installed
bash in /usr/gnu/bin/bash, add the following line to ~/.login:

        if ( -f /usr/gnu/bin/bash ) exec /usr/gnu/bin/bash --login

(the `--login' tells bash that it is a login shell).

It's not a good idea to put this command into ~/.cshrc, because every
csh you run without the `-f' option, even ones started to run csh scripts,
reads that file.  If you must put the command in ~/.cshrc, use something
like

        if ( $?prompt ) exec /usr/gnu/bin/bash --login

to ensure that bash is exec'd only when the csh is interactive.

If your login shell is sh or ksh, you have to do two things.

First, create an empty file in your home directory named `.bash_profile'.
The existence of this file will prevent the exec'd bash from trying to
read ~/.profile, and re-execing itself over and over again.  ~/.bash_profile
is the first file bash tries to read initialization commands from when
it is invoked as a login shell.

Next, add a line similar to the above to ~/.profile:

        [ -f /usr/gnu/bin/bash ] && [ -x /usr/gnu/bin/bash ] && \
                exec /usr/gnu/bin/bash --login

This will cause login shells to replace themselves with bash running as
a login shell.  Once you have this working, you can copy your initialization
code from ~/.profile to ~/.bash_profile.

I have received word that the recipe supplied above is insufficient for
machines running CDE.  CDE has a maze of twisty little startup files, all
slightly different.

If you cannot change your login shell in the password file to bash, you
will have to (apparently) live with CDE using the shell in the password
file to run its startup scripts.  If you have changed your shell to bash,
there is code in the CDE startup files (on Solaris, at least) that attempts
to do the right thing.  It is, however, often broken, and may require that
you use the $BASH_ENV trick described below.

`dtterm' claims to use $SHELL as the default program to start, so if you
can change $SHELL in the CDE startup files, you should be able to use bash
in your terminal windows.

Setting DTSOURCEPROFILE in ~/.dtprofile will cause the `Xsession' program
to read your login shell's startup files.  You may be able to use bash for
the rest of the CDE programs by setting SHELL to bash in ~/.dtprofile as
well, but I have not tried this.

You can use the above `exec' recipe to start bash when not logging in with
CDE by testing the value of the DT variable:

        if [ -n "$DT" ]; then
                [ -f /usr/gnu/bin/bash ] && exec /usr/gnu/bin/bash --login
        fi

If CDE starts its shells non-interactively during login, the login shell
startup files (~/.profile, ~/.bash_profile) will not be sourced at login.
To get around this problem, append a line similar to the following to your
~/.dtprofile:

        BASH_ENV=${HOME}/.bash_profile ; export BASH_ENV

and add the following line to the beginning of ~/.bash_profile:

        unset BASH_ENV