Prerequisites

• Zsh should be installed (v4.3.9 or more recent would do but we prefer 5.0.8 and newer).
• Curl or Wget should be installed.
• Git should be installed (v2.4.11 or higher recommended).

Installing oh-my-zsh in Ubuntu Linux

Installation of Oh My Zsh can be done by using “Curl” or “Wget” commands in your terminal. Make sure either of one utility is installed in the OS, if not install them along with git by running the following apt command.

$ sudo apt install curl wget git

Then we install zsh by,

$ sudo apt install zsh

Make sure zsh is correctly installed,

$ zsh --version

Installing ZSH will not modify and set it as the default shell. We have to modify the settings to make ZSH our default shell. Use the “chsh” command with '-s' flag to switch the default shell for the user.

$ echo $SHELL
$ chsh -s $(which zsh) 
or 
$ chsh -s /usr/bin/zsh

Next, install Oh My Zsh via the command-line with either curl or wget as shown.

$ sh -c "$(curl -fsSL https://raw.githubusercontent.com/ohmyzsh/ohmyzsh/master/tools/install.sh)"

or,

$ sh -c "$(wget https://raw.githubusercontent.com/ohmyzsh/ohmyzsh/master/tools/install.sh -O -)"

Congratulations! You have successfully installed Oh My Zsh on your ubuntu machine!