tmux the terminal multiplexer is one of those brilliant tools I use all day. I am not a tmux expert, nor do I have any need to be. What follows is the bare minimum you need to know to feel productive in tmux, written for some work colleagues.
The following assumes you have not configured or tweaked tmux in any way opting for the default settings.
From the command line to start or connect to tmux
tmux
start a new tmux sessiontmux ls
view the current active sessionstmux attach -t 0
attach to one of the tmux sessions listed fromls
where you replace 0 with some number
Once inside tmux
Ctrl+B d
detach from the current session- To quit the current session type and enter exit till you are kicked out and you can use this to close sessions you have split horizontally or vertically
Ctrl+B s
view the current active sessions, then use up and down keys to highlight and enter to selectCtrl+B '
split the current session window horizontallyCtrl+B %
split the current session window verticallyCtrl+B Alt+↓
expand the current active session window down, if you have split horizontally you can do this, you can push the Alt+↓ key multiple times to keep pushing downCtrl+B Alt+↑
expand the current active session window up, if you have split horizontally you can do this, you can push the Alt+↑ key multiple times to keep pushing downCtrl+B Alt+→
expand the current active session window right, if you have split vertically you can do this, you can push the Alt+→ key multiple times to keep pushing rightCtrl+B Alt+←
expand the current active session window left, if you have split vertically you can do this, you can push the Alt+← key multiple times to keep pushing leftCtrl+B ↓
move the current active session window to the one belowCtrl+B ↑
move the current active session window to the one aboveCtrl+B →
move the current active session window to the one rightCtrl+B ←
move the current active session window to the one leftCtrl+B [
scroll modeCtrl+B space
start copy/yank mode when in scroll modeCtrl+B w
copy selection in scroll mode
Thats about all you need. Its all I ever use on a day to day basis.