How to use tmux, a cheat sheet

I think we know that screen is officially old news and most modern Linux systems switched to tmux as the recommended multiplexer with RHEL 8. Recently I had a discussion amongst my DBA gang for tmux migration and decided to write this. If you’re still using screen, now’s the time to upgrade: tmux is fun! (I know I’m late in the party but better late than never)

This tmux cheat sheet combins session management, logging, reloading config, and scrolling commands in a quick reference format. You can also configure the tmux commands identical to screen by config file (using Ctrl-a).

Tmux Demo Session

Tmux Session Management

Action	Command / Shortcut
Start new session	tmux new -s session_name
List sessions	tmux ls
Attach session	tmux attach -t session_name tmux a (last session)
Detach session	Ctrl + b then d
Kill session	tmux kill-session -t session_name (or connect session and exit)
Attach a session	tmux attach-session -t session_name
Forcefully take-over a session	tmux attach-session -d -t session_name

Tmux Logging

Action	Command
Start logging current pane	tmux pipe-pane -o 'cat >> ~/tmux.log'
Stop logging	tmux pipe-pane

Tmux Reload Config

Action	Command / Shortcut
Reload config	tmux source-file ~/.tmux.conf (from shell)
Reload config (inside tmux)	Ctrl + b then : then source-file ~/.tmux.conf

Tmux Scrolling / Copy Mode

Action	Command / Shortcut
Enter copy/scroll mode	Ctrl + b then [
Scroll up/down	Arrow keys, Page Up / Page Down
Exit copy mode	q or Esc
Enable mouse scrolling	Add “set -g mouse on” to ~/.tmux.conf and reload

Tmux Key Bindings

Action	Shortcut
Detach session	Ctrl + b then d
List sessions	Ctrl + b then s
Rename session	Ctrl + b then $
New window	Ctrl + b then c
Split horizontally	Ctrl + b then "
Split vertically	Ctrl + b then %
Navigate panes	Ctrl + b then Arrow keys

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Configuration customization

You can customize using tmux.conf configuration file further with additional bind keys for your workflow!

If you’re habituated to screen command you can change the default shortcut command from “Ctrl-b” to “Ctrl-a” using configuration. There’s more power in the configuration, have a look.

tmux.conf: Key Settings & Bindings

Action	Command / Config Line
Enable default pane logging to timestamped file	set-option -g default-command ‘tmux pipe-pane -o “cat >>~/tmxlogs/tmx-#{session_name}-\`date +%Y%m%dT%H%M%S\`.log”; /bin/bash -l’
Enable mouse support	set -g mouse on
Increase scrollback/history buffer size	set -g history-limit 10000
Reload tmux config shortcut (prefix + r)	bind r source-file ~/.tmux.conf \; display-message "Config reloaded!"
Unbind default prefix key (Ctrl+b)	unbind C-b
Set prefix key to Ctrl+a (Screen style)	set-option -g prefix C-a
Reload config with prefix + Shift + R	bind-key R source-file ~/.tmux.conf \; display-message "Config reloaded!"

Sample ~/.tmux.conf

You can use the following configuration:

# vim ~/.tmux.conf

# Enable default logging 
set-option -g default-command 'tmux pipe-pane -o "cat >>~/tmxlogs/tmx-#{session_name}-\`date +%Y%m%dT%H%M%S\`.log"; /bin/bash -l'

# Enable mouse support for scrolling and pane selection
set -g mouse on  

# Increase scrollback / log history buffer size
set -g history-limit 10000

# Reload config shortcut - Ctrl+b, R to reload config changes
bind r source-file ~/.tmux.conf \; display-message "Config reloaded!"

# Screen compatible commands settings
unbind C-b                        # Unbind default prefix
set-option -g prefix C-a          # Set prefix to Ctrl+a (same as screen)

To make use of configuration changes for the first time you need to run

tmux source ~/.tmux.conf

Once you have added “Reload config shortcut” you just need to press: Ctrl-a, r to reload the changes.