zsh-howto
set zsh as the default terminal (need re-login)
chsh -s $(which zsh)
https://askubuntu.com/questions/131823/how-to-make-zsh-the-default-shell
FIXED: can't work even after re-login
change the /bin/bash to be /bin/zsh in /usr/passwd file:

ref:
zsh check where alias/env comes from
zsh -ixc : 2>&1 | grep thingToSearchHere