How to make ZSH the default shell?

Just using chsh:

chsh -s $(which zsh)

without sudo should work. If you use sudo it will change the shell not for your working user but for root

Finally, log out of your computer and log back in.

Troubleshooting:

• Do you have zsh installed (ii)? dpkg -l zsh
• Is your shell set to zsh? Last field of grep $USER /etc/passwd
• Is Zsh a valid login shell? grep zsh /etc/shells

I found this on superuser forum

Open /etc/passwd:

sudo vi /etc/passwd

Find the line with your username:

username:x:1634231:100:Your Name:/home/username:/bin/bash

and replace bash with zsh:

username:x:1634231:100:Your Name:/home/username:/bin/zsh

Log out and log in back for the changes to take effect.

You may also do this:

open your bashrc file in your favourite editor

sudo nano ~/.bashrc

then add the line below top of the file

exec zsh

It will execute the command every time you load the terminal and run your zsh shell.