tmux: A Comprehensive Guide

tmux (terminal multiplexer) lets you run multiple terminal sessions inside a single window. You can split windows into panes, detach and reattach sessions, and keep programs running even after disconnecting from SSH.

This guide covers tmux from beginner to advanced usage.

1. What is tmux?

tmux is a terminal multiplexer that allows you to:

Run multiple shells in one terminal
Split the terminal into panes
Detach sessions and reattach later
Persist long-running tasks

Common use cases:

Remote server work
Long-running builds or training jobs
Managing multiple terminals efficiently

2. Installing tmux

Linux (Debian/Ubuntu)

sudo apt install tmux

Linux (RHEL/CentOS)

sudo yum install tmux

macOS (Homebrew)

brew install tmux

Verify Installation

tmux -V

3. Core Concepts

tmux has a simple hierarchy:

Server → runs in background
Session → collection of windows
Window → like a tab
Pane → split within a window

Session
 ├── Window 1
 │    ├── Pane A
 │    └── Pane B
 └── Window 2
      └── Pane A

4. Starting and Exiting tmux

Start a New Session

tmux

Start with a Name

tmux new -s mysession

Detach from a Session

Press:

Ctrl-b d

Exit tmux

Type exit in all panes
Or kill the session explicitly

tmux kill-session -t mysession

5. Sessions

List Sessions

tmux ls

Attach to a Session

tmux attach -t mysession

Rename a Session

Ctrl-b $

Switch Between Sessions

tmux switch -t mysession

6. Windows

Create a New Window

Ctrl-b c

List Windows

Ctrl-b w

Switch Windows

Next: Ctrl-b n
Previous: Ctrl-b p
By number: Ctrl-b 0–9

Rename Window

Ctrl-b ,

Close Window

Ctrl-b &

7. Panes

Split Panes

Vertical split:

Ctrl-b %

Horizontal split:

Ctrl-b "

Move Between Panes

Ctrl-b ↑ ↓ ← →

Resize Panes

Hold prefix, then:

Ctrl-b Ctrl-Arrow

Close a Pane

Type exit or:

Ctrl-b x

8. The Prefix Key

By default, tmux uses:

Ctrl-b

You press the prefix before any tmux command.

Example:

Ctrl-b c   # create new window
Ctrl-b %   # split pane vertically

9. Copy Mode & Scrollback

Enter Copy Mode

Ctrl-b [

Navigation (vi-style by default)

Move: h j k l
Page up/down: Ctrl-u / Ctrl-d
Search: /

Copy Text

Enter copy mode
Press Space to start selection
Move cursor
Press Enter to copy

Paste

Ctrl-b ]

10. Customizing tmux (`.tmux.conf`)

Create or edit:

~/.tmux.conf

Common Customizations

Change Prefix to Ctrl-a

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

Enable Vi Mode

setw -g mode-keys vi

Faster Key Response

set -s escape-time 0

Reload Config

bind r source-file ~/.tmux.conf \; display "Reloaded!"

Then:

Ctrl-b r

11. Mouse Support

Enable mouse support:

set -g mouse on

This allows:

Clicking panes
Resizing panes
Scrolling

12. tmux + SSH Workflow

A very common pattern:

SSH into server
Start tmux
Run long tasks
Detach
Disconnect SSH
Reconnect later and reattach

ssh user@server
tmux attach -t work

This prevents job loss on disconnect.

13. Useful Key Bindings Cheat Sheet

Action	Key
New session	`tmux new -s name`
Detach	`Ctrl-b d`
New window	`Ctrl-b c`
Split vertical	`Ctrl-b %`
Split horizontal	`Ctrl-b "`
Switch panes	`Ctrl-b arrows`
Copy mode	`Ctrl-b [`
Paste	`Ctrl-b ]`
Rename window	`Ctrl-b ,`
Kill pane	`Ctrl-b x`

14. Troubleshooting & Tips

tmux Feels Laggy

set -s escape-time 0

Colors Look Wrong

Ensure:

export TERM=xterm-256color

And in tmux:

set -g default-terminal "screen-256color"

Nested tmux Sessions

Use:

tmux attach -t session

Instead of starting tmux inside tmux.

15. Further Resources

Final Notes

tmux is one of those tools that feels awkward at first, then becomes indispensable. Learn a few commands, customize gradually, and let muscle memory do the rest.

Happy multiplexing 🚀

Tmux: A Comprehensive Guide