Tmux is a terminal multiplexer that lets you have multiple virtual terminals and also split windows and have multiple panes and tabs. Another nice feature is if you are connecting over SSH and using Tmux, Tmux can keep your session going even if you disconnect and re-connect later. An alternative to Tmux is GNU Screen.

In Debian, you can simple use the system package manager to install:

sudo apt install tmux
tmux -V  # Check version

To build from source, download sources from the Tmux GitHub Releases. Building is pretty simple, it has few dependencies and compiles quickly.

# Install buidl dependencies
sudo apt install libevent-dev ncurses-dev build-essential bison pkg-config
 
wget https://github.com/tmux/tmux/releases/download/3.1c/tmux-3.1c.tar.gz
tar -zxf tmux-3.1c.tar.gz
cd tmux-3.1c/
 
# Identify the options you want
./configure --help | less
./configure
make
./tmux -V
sudo make install  # Optional

To initialize a tmux session, simply invoke tmux.

tmux

To get help information and a list of commands, use:

man tmux
tmux --help
tmux list-keys
tmux list-commands
# Within tmux press ''CTRL-b ?''

With mouse enabled, you can click between split windows and use the mouse to resize. You can also right click on panes and in the bottom left corner to switch windows and manage processes. It adds a lot of really nice functionality.

You must specify setw -g mouse on in a tmux conf file. For example:

.tmux.conf

# ~/.tmux.conf

# Enable mouse
set -g mouse on

# Then run tmux as normal
tmux
# OR to be explicit
tmux source-file ~/.tmux.conf

When you start tmux, you are creating a “session”. You can have multiple sessions and they are identified by a number or a name.

# List active sessions
tmux ls
 
# Connect to last active session
tmux attach
 
# Connect to a session by its numeric ID
tmux attach -t 0
 
# Create a new named session
tmux new -s mysession
 
# Create a new named session + run vim in detached mode
tmux new -s mysession -d "vim"
 
# Connect to a session by name
tmux attach -t mysession

Once you are in a session and you want to disconnect,

# Use the shell command
tmux detach
 
# Or use the keybinds
CTRL-b d

To kill a session, simply exit the shell like normal with exit or CTRL-d, or you can send a tmux command to kill the session.

# End a session by name
tmux kill-session -t myapp

The top level object is a session. A session contains windows, and a window contains panes. Here are commands related to windows. Like most things in tmux, you can use the shell command, or the keybind.

tmux new-window
tmux list-windows
tmux select-window -t 1
tmux rename-window # Renames current window
 
tmux split-window
tmux split-window -h
 
tmux swap-pane -\[UDLR\]

Most of these keybinds must be preceeded with the CTRL-b chord.

• Create a new window - c
• List window - w
• Select a window - (the number of the window)
• Rename windows - ,
• Kill window - &
• Next window - n
• Previous window - p
• Last window - l
• Split window horizontally in two panes - “
• Split window vertically in to two panes - %
• Set even split horizontally - ALT-1
• Set even split vertically - ALT-2

A pane is the lowest level of hierarchy in screen organizing. The top level is the session, then the session has windows, and a window is made up of panes.

Most of these need to be preceeded by CTRL-b followed by one of the following keybinds:

• Switch active pane - up/down/left/right arrow
• Next pane - o
• Previous pane - ;
• Kill pane - x
• Break out pane in to window - !
• Resize pane 1 unit - CTRL plus left/right/up/down arrow
• Resize pane 5 units - ALT plus left/right/up/down arrow
• Swap pane up/down - { or }
• Rotate pane up/down - CTRL-o or ALT-o

You can use tmux send-keys to send keystrokes to a specific session.

All keys including functions, alt, home, page up, arrow keys, and even mouse actions can all be emulated. Here is a full list of keys from the source code of tmux: https://github.com/tmux/tmux/blob/ec7f5305b1a6e5548f0769f988e76b01ec293dcc/key-string.c#L33-L100

# Send some vim commands to a session
tmux send-keys -t mysession "i" "hello" Enter Escape ":w! test.txt" Enter

Every command is assumed to begin with the chord, which by default is CTRL-b. Press CTRL-b and then release before pressing the next action key.

• Toggle scrolling with CTRL-b [
• Switch to next pre-defined layout: CTRL-b SPACE