Can I make tmux scroll from my trackpad?
The mode is referred to as "copy mode" and as long as you're running tmux 1.5 or higher you can add:
setw -g mode-mouse on
to your ~/.tmux.conf file and tmux will automatically enter and exit copy mode when you use the scroll wheel on your mouse.
As a bonus, this option allows you to select the tmux pane with your mouse:
set -g mouse-select-pane on
As seen in this related issue: https://stackoverflow.com/questions/11832199/tmux-set-g-mouse-mode-on-doesnt-work
The command to enable scrolling & easy copy to clipboard highlighting is the following:
set -g mouse on