tmux is a terminal multiplexer that allows you to create, access, and control multiple terminal sessions from a single window. It’s essential for managing complex development workflows with persistent sessions.

What It Does

tmux enables:

• Multiple Sessions: Run separate terminal sessions that persist
• Window Management: Split windows into panes
• Session Persistence: Sessions survive disconnections (SSH, terminal close)
• Background Work: Run long-running processes that outlive your terminal
• Session Sharing: Attach to the same session from different terminals

Key Concepts

Sessions

A tmux session is a independent collection of terminal windows.

# Create new session
tmux new -s mysession

# Detach (leave running in background)
Ctrl-b d

# List sessions
tmux ls

# Attach to session
tmux attach -t mysession

# Kill session
tmux kill-session -t mysession

Windows

Each session can contain multiple windows (like browser tabs).

# Create new window
Ctrl-b c

# Switch to next window
Ctrl-b n

# Switch to previous window
Ctrl-b p

# List windows
Ctrl-b w

# Rename current window
Ctrl-b ,

# Kill window
Ctrl-b &

Panes

Split windows into rectangular panes.

# Split horizontally (top-bottom)
Ctrl-b "

# Split vertically (left-right)
Ctrl-b %

# Navigate between panes
Ctrl-b arrow-key

# Resize pane
Ctrl-b :resize-pane -D 5   # Down 5 lines

# Toggle pane zoom
Ctrl-b z

# Kill pane
Ctrl-b x

My Setup

I use tmux as part of the Gastown multi-agent workspace, running multiple specialized sessions:

• Mayor Session: AI coordinator with full town context
• Polecat Sessions: Worker agents for task execution
• Witness Session: Monitors worker health and lifecycle

This setup allows running 10-20 concurrent agents while maintaining visibility into all activities.

Custom Configuration (~/.tmux.conf)

# Enable mouse support
set -g mouse on

# Set scrollback history
set -g history-limit 10000

# Use vim keybindings in copy mode
setw -g mode-keys vi

# Faster command sequence
set -s escape-time 0

# Start window numbering at 1
set -g base-index 1

# Pane numbering
set -g pane-base-index 1

Essential Keybindings

Copy Mode (vim-style)

# Enter copy mode
Ctrl-b [

# Navigate (vim keys)
h j k l    # Left, down, up, right
gg         # Go to top
G          # Go to bottom

# Select text
v          # Start selection
V          # Select line

# Copy selection
y          # Yank (copy)

# Exit copy mode
q          # or Esc

Installation

# macOS
brew install tmux

# Ubuntu/Debian
sudo apt install tmux

# RHEL/Fedora
sudo dnf install tmux

Related Tools

• Gastown: Uses tmux for multi-agent session management
• tmuxinator: Manage complex tmux configurations as YAML files
• tpm: Plugin manager for tmux

Resources

• tmux GitHub
• tmux cheatsheet

Tags: Terminal, Productivity, Developer Tools