Force default shell to Bash. This is especially useful when user does not exist in /etc/passwd. Place this snippet at the end of /etc/profile or ~/.profile.

profile

case $- in
   *i*)
      # If $BASH is not defined then we're already in a Bash shell
      if [ -z "$BASH" ]; then
         BASH_BIN=$(command -v bash)
         # Ensure Bash is installed on the system, then switch shells
         if [ -x "$BASH_BIN" ]; then
            export SHELL="$BASH_BIN"
            exec "$BASH_BIN"
         fi
      fi
      ;;
esac