tmux

Updated

September 4, 2026

Overview

tmux is a terminal multiplexer: multiple windows and panes inside detachable sessions that survive SSH disconnects. Prefer it over nohup for interactive long-lived remote work, and over ad-hoc background jobs when you need to reattach and see output. For production services still prefer systemd.

Syntax

tmux [command] [options]
tmux [-L socket-name] [-S socket-path] [-f file]

Most daily use is either bare tmux or a short subcommand (new, attach, ls, kill-session).

Install (Ubuntu)

sudo apt update
sudo apt install tmux
tmux -V

Prefix key

Default prefix: Ctrl-b, then a command key. (Many people rebind to Ctrl-a.)

After prefix Action
c New window
, Rename window
n / p Next / previous window
0–9 Select window by index
w Window list
& Kill window
% Split pane left/right
" Split pane top/bottom
o / arrow keys Cycle / move between panes
; Last pane
x Kill pane (confirm)
z Zoom toggle (pane fullscreen)
{ / } Swap panes
Space Cycle pane layouts
d Detach session
s Session list
$ Rename session
[ Copy / scroll mode
] Paste buffer
? List keys
: Command prompt

Common CLI commands

Command Description
tmux New session (default name)
tmux new -s NAME Named session
tmux new -d -s NAME [cmd] Detached session (optional command)
tmux ls List sessions
tmux attach -t NAME Attach
tmux attach -d -t NAME Attach and detach others
tmux switch -t NAME Switch (from inside tmux)
tmux kill-session -t NAME Kill session
tmux kill-server Kill all sessions (careful)
tmux list-windows -t NAME Windows in session

Key Use Cases

  1. Survive laptop sleep / SSH drops during deploys
  2. Pair multiple panes (logs + editor + shell)
  3. Long builds or trainers you can reattach to
  4. Named sessions per project (tmux new -s api)

Examples with Explanations

Example: create, detach, reattach

tmux new -s deploy
# ... work ...
# Ctrl-b d
tmux ls
tmux attach -t deploy
# short form:
tmux a -t deploy

Core workflow. Detach leaves processes running on the server.

Example: start detached job session

tmux new -d -s train 'python3 train.py 2>&1 | tee train.log'
tmux attach -t train

Session exists immediately; attach when you want the TTY.

Example: nested SSH-safe habit

ssh host
tmux new -s work || tmux attach -t work

Create-or-attach pattern for a daily session.

Example: splits for ops

Inside a session:

  1. Ctrl-b % — vertical split (side by side)
  2. Ctrl-b " — horizontal split
  3. Ctrl-b z — zoom the pane you care about
  4. Run journalctl -fu nginx in one pane, shell in another

Example: scripted window layout

tmux new -d -s app
tmux rename-window -t app:0 shell
tmux new-window -t app -n logs 'journalctl -f'
tmux new-window -t app -n top 'htop'
tmux split-window -h -t app:shell
tmux attach -t app

Good for standardizing a “ops dashboard” session.

Example: send keys to a session (automation)

tmux new -d -s patch
tmux send-keys -t patch 'sudo apt update && sudo apt upgrade' C-m

Use sparingly; prefer scripts over pseudo-interactive automation when possible.

Example: shared socket / pair-ish access

tmux -S /tmp/pair.sock new -s pair
# other user (permissions permitting):
tmux -S /tmp/pair.sock attach -t pair

For real pairing, tools like tmate or proper access control may be better.

Example: minimal ~/.tmux.conf

set -g mouse on
set -g history-limit 50000
set -g base-index 1
setw -g pane-base-index 1
set -g renumber-windows on
# rebind prefix to Ctrl-a (optional):
# unbind C-b
# set -g prefix C-a
# bind C-a send-prefix

Reload from inside tmux: Ctrl-b : then source-file ~/.tmux.conf.

Example: copy mode (scrollback)

Ctrl-b [ → move with arrows/PageUp → Space begin selection → Enter copy (bindings vary with mode-keys vi/emacs) → Ctrl-b ] paste.

With mouse on, scroll and select often work directly.

Safety

  • tmux kill-server ends all sessions for that server socket — confirm tmux ls first.
  • Detached sessions still consume resources; clean up dead project sessions.
  • Do not run secrets printing in shared sessions.
  • Nested tmux (local + remote) confuses prefixes — use a different remote prefix or SSH directly into remote tmux only.

Notes & Pitfalls

  • Environment variables are captured at session start; re-login SSH agent sockets often need tmux setenv or plugin tooling after laptop sleep.
  • TERM/COLORTERM mismatches cause weird colors — prefer tmux -2 legacy force or correct terminal-overrides in conf for modern terminals.
  • Clipboard integration needs xclip/wl-clipboard and conf bindings on desktop Linux.
  • Version differences: Ubuntu LTS tmux may lag plugin ecosystem features — check tmux -V.
  • Prefer one session per task rather than infinite windows without names.

Additional Resources

  • man tmux
  • tmux list-keys / tmux list-commands