Tmux

About Tmux

Tmux is a virtual terminal and is useful in a remote environment (like after connecting with ssh) since lets you to call commands and softwares in one or more virtual windows, which will not be interrupted if the network goes down or you need to terminate your local terminal (ie you need to go home :-)). From the tmux man pages:

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 is already installed in our core shared machine and should be started immediately after connecting with SSH, on the remote environment: you could even install and start tmux in your local environment, but if you connect to the remote machine in a tmux local terminal, your tasks will be interrupted when network has issues or you local environment is turned off.

Hint

The main idea with tmux is to start a session remotely, in order to detach and leave your process in background, even after logging out the remote environment. All the information returned to the virtual terminal will be available when reconnecting to the same tmux session and window, even by using another connection or another device.

Tmux sessions

You should create a tmux session using different names, for example using the name of projects you are working on. This let you to define multiple sessions and to work at different projects at the same time, and let you to switch from one terminal to another if your are waiting for your program to finish. Here is how to start a new tmux session:

$ tmux new -s <session name>

where <session name> will be the name of your session. By creating a new session, a new terminal inside a tmux window is started. To connect to an existent tmux session, first display your active and running session names with:

$ tmux ls

Then attach to a session by providing the session name with:

$ tmux attach -t <session name>

Tmux control command

After a tmux terminal is started, you will start a new terminal inside a tmux session and you can work in the same way you could work outside tmux. If you need to take control to the tmux terminal, you need a combination of a prefix key, which is C-b (Ctrl-b) by default, followed by a command key. For instance, to leave the current tmux session, leaving the terminal and its processes running in background you need to press Ctrl-b and then the letter d (which stands for detach from your current session). Other useful command keys are:

Command

Behavior

Ctrl-b + d

Detach the current session

Ctrl-b + c

Create a new window

Ctrl-b + w

Move across window using arrow keys

Ctrl-b + <num>

Switch to the window num

Ctrl-b + %

Split window vertically

Ctrl-b + $

Rename session

Ctrl-b + ,

Rename window

Ctrl-b + "

Split window horizontally

Ctrl-b + <space>

Move from horizontal split to vertical and viceversa

Ctrl-b + s

Move across sessions using arrow keys

Here are some resources where you can find more information and tips:

Terminate a session

In order to terminate and close a session, you have to exit from all your opened windows inside a session. To do this, you simply exit on the window terminals like any other terminal outside tmux. When you close the last window, you will see:

[exited]

on your terminal, and by doing tmux ls you will not see your session anymore (or you will see no server running on /tmp/tmux-XXXX/default) if you have no tmux session running

Customize Tmux

You can change your tmux appearance, or change control command keys. You need to create a .tmux.conf file in your home directory, in which define the stuff you need. Here are some resources where you can find how to customize tmux: