tmux Cheat Sheet

tmux keeps your programs running on the server after your SSH connection drops. Every shortcut below starts with the prefix, Ctrl-b: press that, let go, then press the next key.

Sessions

tmux                          # start a new session
tmux new -s deploy            # start one with a name
tmux ls                       # list sessions
tmux attach                   # go back to the latest one
tmux attach -t deploy         # go back to this one
tmux kill-session -t deploy   # end one
tmux kill-server              # end all of them

Ctrl-b d      detach (everything keeps running)
Ctrl-b s      choose a session from a list
Ctrl-b $      rename this session

Windows

Windows are like tabs.

Ctrl-b c      new window
Ctrl-b n      next window
Ctrl-b p      previous window
Ctrl-b 0..9   go to window number
Ctrl-b w      choose from a list
Ctrl-b ,      rename this window
Ctrl-b &      close this window (asks first)

Panes

Panes split a window.

Ctrl-b %      split left and right
Ctrl-b "      split top and bottom
Ctrl-b arrow  move to the next pane
Ctrl-b o      next pane
Ctrl-b z      zoom this pane (press again to go back)
Ctrl-b x      close this pane (asks first)
Ctrl-b !      turn this pane into a window
Ctrl-b Space  change the layout
Ctrl-b q      show pane numbers
Ctrl-b {      swap with the previous pane
Ctrl-b }      swap with the next pane

To resize, hold Ctrl and the prefix’s b, then press an arrow key, or use :resize-pane -D 5 for down by 5.

Scroll and copy

Your mouse wheel may not work until you turn it on (below), so use copy mode:

Ctrl-b [      enter copy mode, then arrows or PgUp to scroll
q             leave copy mode
Space         start selecting
Enter         copy the selection
Ctrl-b ]      paste

In copy mode, press / to search forward and ? to search backward. If you use Vim keys, set them in the config (below).

Commands

Ctrl-b :      type a tmux command
Ctrl-b ?      list every shortcut
Ctrl-b t      show a clock

tmux send-keys -t deploy 'uptime' Enter        # type into a session from outside
tmux new -d -s job './backup.sh'               # run something in the background
tmux capture-pane -pt deploy | tail -n 20      # read what's on its screen

Run the same thing on every pane

Ctrl-b :setw synchronize-panes on
Ctrl-b :setw synchronize-panes off

That’s useful with one pane per server. Be careful, as everything you type goes to all of them.

Two people logged in as the same user can both attach, and see the same screen:

tmux new -s pair            # first person
tmux attach -t pair         # second person

A small config

Put this in ~/.tmux.conf:

set -g mouse on                     # scroll and click with the mouse
set -g history-limit 50000          # keep more scrollback
set -g base-index 1                 # number windows from 1
setw -g pane-base-index 1           # and panes
setw -g mode-keys vi                # Vim keys in copy mode
set -g escape-time 10               # no lag after Esc in Vim
bind r source-file ~/.tmux.conf \; display "Reloaded"

To load it into a running session: tmux source-file ~/.tmux.conf.

Prefer Ctrl-a as the prefix, as in GNU screen? Add these lines:

unbind C-b
set -g prefix C-a
bind C-a send-prefix

When things look wrong

no sessions: the server rebooted, or the last session ended. tmux keeps sessions in memory, so they don’t survive a reboot.
sessions should be nested with care: you’re already inside tmux, as with one on your laptop and another on the server. Press the prefix twice to reach the inner one.
open terminal failed: missing or unsuitable terminal: your TERM isn’t known on the server. Run TERM=xterm-256color tmux.
Your screen stops updating, or shows only dots: another smaller client is attached. Use tmux attach -d, which detaches others.
SSH keys or DISPLAY stopped working in an old session: the session kept the settings from when it was created. Start a new one, or update them by hand.

Other things you may need

Vim Cheat Sheet
Linux Troubleshooting Cheat Sheet
The SSH Config Generator, to keep SSH connections alive