Ubuntu 22.04 Tmux

tmux — terminal multiplexer

Basics

Description Quote from man page

tmux is a terminal multiplexer: it enables a number of terminals to be created, accessed, and controlled from a single screen. tmux may be detached from a screen and continue running in the background, then later reattached.

Tmux can do a number of things.

In this module we are just going to concentrate on solving the problem of something going wrong with our SSH connection.

If we lose our SSH terminal connection, processes we were running will be sent a SIGHUP signal.

SIGHUP

Let’s go straight to an example of using tmux to solve this problem.

On our server, let’s run/start tmux:

tmux

That’s it.

Now let’s run a program and see what happens when we disconnect:

$EDITOR test-txt-file

Hello world
I am writing or doing something important.
I hope I don’t disconnect and lose this

Now just close the terminal—do not save and/or exit the text editor, just close the terminal.

Open another terminal and reconnect to your server.

Use the command tmux ls to list your tmux sessions:

tmux ls

My output:

0: 1 windows (created Mon Jun  1 06:41:43 2020) [140x14]

I am going to reconnect to my tmux session 0 with the command:

tmux attach -t 0

And that’s it.

Tmux also solves the problem of your SSH session closing due to inactivity:

packet_write_wait: Connection to 192.248.157.27 port 22: Broken pipe

Note: You can run the same tmux session in more than one terminal at the same time. Open 3 terminals and log into the server. In each terminal:
tmux attach -t 0
All will be updated in real time. If you exit tmux by typing exit in one terminal, the tmux session will end and exit on all 3 terminals. If you don’t want that, just close the terminal without typing exit.

You do not need tmux installed on your local computer, just the computer (server) you are connecting to.

tmux is installed by default on Ubuntu Server 18.04, but if you want to install it on your desktop or if it’s been removed from your server and you want to reinstall: apt install tmux

Scrolling in tmux

Press Ctrl+b followed by [. Now you can scroll up and down with arrow keys. Press q to quit scroll mode.

Managing tmux Sessions and Windows

To close a tmux window and later come back to it, you can use the following steps:

Detaching from a tmux Session (Without Terminating It)

Detach from the current tmux session by pressing:

Ctrl-b d

This will leave the session running in the background, allowing you to close the terminal or work on other tasks.

Reattaching to a tmux Session

To reattach to a detached session, use:

tmux attach-session

This command will reconnect you to the most recently detached session.

If you have multiple sessions, list them with:

tmux list-sessions

Then, reattach to a specific session by its name or number:

tmux attach-session -t <session_name>

If another client is attached to the session, you can forcefully detach them and reattach using:

tmux attach-session -t <session_name> -d

Closing a tmux Window

To close a specific window in tmux, press:

Ctrl-b &

Confirm with y to kill the window.

Alternatively, you can type exit in the shell of the window to close it.

If you prefer using commands, run:

tmux kill-window -t <window_number>

By detaching instead of killing the session, you ensure that your work is preserved and can be resumed later.