2 examples for chsh
# use option -s to set the shell of the current user (yourself ; )
# use which to find the full path of the shell
# $ which zsh
# => /usr/bin/zsh
# then set your new shell
#
# note:
# some apps have an explicit shell path
# GNUShell expects something like
# shell "/usr/bin/zsh" in its .screenrc
#
chsh -s /usr/bin/zsh