tmux and Screen
tmux and screen are so-called terminal multiplexer that allows you to run multiple terminal sessions from inside a single terminal or SSH-session. The EV3 brick has a tmux session running in the background, so that if the SSH-connection fails the program you are running continues to be executed, instead of terminating it with the SSH-session.
For the Online-RoboLab, we use the Mothership server as hop with a screen session holding the tmux session.
Useful Commands
| Command | Function |
|---|---|
tmux | Starts a new unnamed tmux session |
tmux a | Attach to last tmux session |
tmux a [session name] | Attach to tmux session with the name [session name] |
tmux ls | Lists all tmux sessions that are currently open |
| Command | Function |
|---|---|
screen | Starts a new unnamed screen session |
screen -x | Attach to last screen session |
screen -list | Lists all screen sessions that are currently open |
Useful Hotkeys
The hotkeys (obviously) only work, when you are inside a running tmux session.
| Hotkey | Function |
|---|---|
Ctrl + b followed by hitting d | Detach the tmux session |
Ctrl + b followed by hitting s | Lists all open tmux sessions |
Ctrl + b followed by hitting c | Create a new tab |
Ctrl + b followed by hitting n | Switch to next tab |
Ctrl + b followed by hitting p | Switch to previous |
Ctrl + b followed by hitting [ | Allows you to enter scrolling mode in tmux. To exit scrolling mode press Esc |
Ctrl + b followed by hitting " | Split current pane horizontally |
Ctrl + b followed by hitting % | Split current pane vertically |
Ctrl + b followed by hitting arrow keys | Switch between selected sub-pane |
Ctrl + b followed by hitting z | Zoom into currently selected sub-pane |
The hotkeys (obviously) only work, when you are inside a running screen session.
| Hotkey | Function |
|---|---|
Ctrl + a followed by hitting d | Detach the screen session |
Ctrl + a followed by hitting c | Create a new tab |
Ctrl + a followed by hitting n | Switch to next tab |
Ctrl + a followed by hitting p | Switch to previous |
Advanced stuff
The EV3 brick has a hidden tmux session running that you are not supposed to attach to.
Attaching to this secret session will not work with the regular commands, since you should only attach to that session via the deploy.py.
If you feel confident enough with tmux about not breaking said secret session, you can attach to it by replacing the regular tmux in the commands with the following:
tmux -S /tmp/tmux/shared attach -t robolab-startup
For further reading you can check out the following links: