Managing Remote Terminal Sessions with Tmux

I primarily work on my remote system, using it as my build system to compile images for my target development boards. I prefer to keep alive my remote session for several reasons:

1. The build process can take hours to complete, and if my internet connection is interrupted, the shell session may be disrupted, potentially causing the build to fail.
2. I would like to power off my local systems and return later to monitor the compilation progress.
3. I intend to resume my work right where I left off.

Fortunately, there exists a Linux tool called tmux, which can accomplish much more than the requirements I initially had in mind.

Tmux serves as a terminal multiplexer, enabling you to create and manage multiple shell sessions within a single local system terminal or within a single remote SSH connection. Especially during an SSH session, you don’t need to start another SSH connection to have two terminals open side by side on the remote server.

Let’s explore how to utilize tmux for the management of terminal sessions.

Starting a new session

Launch the terminal on your local system or log in to your remote server via SSH. To create a tmux session, employ the following command:

tmux new -s <sessionName>

An example of this:

tmux new -s buildroot_build

Detaching a tmux session

Pressing Ctrl+d will terminate a tmux session. To detach from the current session while keeping it running, use the following key sequence: Ctrl+b followed by d

List the tmux sessions

The command tmux ls displays all the tmux sessions currently running on the system.

$ tmux ls  
buildroot_build: 1 windows (created Sat Sep  9 21:29:31 2023)  
yocto_build: 1 windows (created Sat Sep  9 21:29:59 2023)

buildroot_build and yocto_build are two tmux sessions alive.

Attaching to a tmux session

From the output of the tmux ls command, you can identify all the tmux session names. To attach to a specific tmux session and resume your work from where you left off, use the following command:

tmux a -t <sessionName>

Let’s say one of tmux session name is yocto_build then to attach to that terminal session, use the command:

tmux a -t yocto_build

Splitting the Terminal pane

This is the best part of working with tmux. If you prefer not to disrupt your current terminal session and need another terminal session on your remote system, you can achieve this without initiating a new SSH session.

To split the terminal pane vertically, press the shortcut Ctrl+b followed by % ( Shift+5)

To split the terminal pane horizontally, press the shortcut Ctrl+b followed by " (Shift+').

Tmux split panes

Switching between the panes

Employ Ctrl+b in conjunction with the arrow keys to navigate between panes.

• To move the cursor to the right pane, use Ctrl+b followed by → (Right Arrow).
• To move the cursor to the left pane, use Ctrl+b followed by ← (Left Arrow).
• To move the cursor to the top pane, use Ctrl+b followed by ↑ (Up Arrow)
• To move the cursor to the bottom pane, use Ctrl+b followed by ↓ (Down Arrow)

Resizing the panes

Hold Ctrl+b, don’t release it and hold one of the arrow keys.

Creating new window

Use the shortcut Ctrl+b followed by c.

Switching between windows

Use the shortcut Ctrl+b followed by n to move to next window. And use Ctrl+b followed by p to move to previous window.

Scrolling in tmux

By default, in tmux, mouse scrolling or Page Up/Down keys do not work. To enable scrolling, press Ctrl+b, followed by [. Now you can use the vim editor navigation keys (j, k, l, h, g etc.) or simple arrow keys and PageUp/Down keys to navigate around terminal text.

While in scrolling mode, you can’t use any other keys

Quit scrolling

Press q to quit scrolling.

I hope this tutorial is helpful. For more information, you can refer to the man page by using the command man tmux.