Tmux uses ctrl+b as default prefix. I rather have it set to ctrl+Space. The space bar is hard to miss. And I use it as leader in VIM, so I like the consistency.
To configure the prefix we need to make a change in the
~/.tmux.conf file. Following the example in the tmux man pages, we make the following addition in the tmux config.
# ~/.tmux.conf unbind-key C-b set-option -g prefix C-Space bind-key C-Space send-prefix
A great resource for learning more about tmux are its man pages. You can read them online here or from the command-line using the following command:
$ man tmux
Or take a look at this book: