tmux

tmux keeps terminal sessions running when you detach or lose an SSH connection. A session contains windows; each window contains one or more panes, each with its own terminal. Detaching leaves those terminals running, but does not protect them from a server reboot.

In your shell, start a named session with tmux new -s work. To return later, use tmux attach -t work; tmux ls lists existing sessions.

Basic Tmux Keybindings

Press Ctrl+B, release it, then press the next key. This prefix tells tmux to interpret the following key as a command rather than send it to the program in the pane.

Keybinding	Description
Ctrl+B d	Detach from current session
Ctrl+B %	Split into left and right panes
Ctrl+B "	Split into top and bottom panes
Ctrl+B then arrow key	Navigate between panes
Ctrl+B x	Close pane
Ctrl+B c	Create new window
Ctrl+B n / Ctrl+B p	Move to the next / previous window
Ctrl+B :	Enter command mode

Configuring Tmux

Store persistent settings in $HOME/.tmux.conf. Open that file from your shell:

vi "$HOME/.tmux.conf"

Put the following tmux commands inside the file, not in your shell. They change the prefix from Ctrl+B to Ctrl+A:

# Set new prefix to Ctrl+A
set -g prefix C-a
unbind C-b
bind C-a send-prefix

Customizing the Status Bar

Add these settings to the same .tmux.conf file to customize the status-bar colors. To apply a saved file to a running tmux server, run tmux source-file "$HOME/.tmux.conf" from your shell.

set -g status-style bg=cyan
set -g window-status-style bg=yellow
set -g window-status-current-style 'bg=red,fg=white'

The Missing Semester command-line environment lesson connects Tmux to shell job control and SSH. Work through detaching and reattaching a session, then compare that behavior with suspending a foreground job using Ctrl-Z. This clarifies which process the shell pauses and what Tmux keeps running.

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