7.16. Screen Usage

Screen or GNU Screen is a terminal multiplexer. In other words, it means that you can start a screen session and then open any number of windows (virtual terminals) inside that session. Processes running in Screen will continue to run when their window is not visible even if you get disconnected.

7.16.1. Install Linux Screen

The screen package should be installed on OpenNAC Enterprise nodes. You can check if it is installed on your system by typing:

screen --version

If not, install it:

dnf install -y screen

7.16.2. Starting Linux Screen

To start a screen session, simply type screen in your console:

screen

This will open a screen session, create a new window, and start a shell in that window.

Now that you have opened a screen session, you can get a list of commands by typing:

Ctrl+a ?

7.16.3. Starting Named Session

Named sessions are useful when you run multiple screen sessions. To create a named session, run the screen command with the following arguments:

screen -S session_name

It’s always a good idea to choose a descriptive session name.

7.16.4. Working with Linux Screen Windows

When you start a new screen session, it creates a single window with a shell in it.

You can have multiple windows inside a Screen session.

To create a new window with shell type Ctrl+a c, the first available number from the range 0…9 will be assigned to it.

Below, are some most common commands for managing Linux Screen Windows:

  • Ctrl+a c: Create a new window (with shell).

  • Ctrl+a ": List all windows.

  • Ctrl+a 0: Switch to window 0 (by number).

  • Ctrl+a A: Rename the current window.

  • Ctrl+a S: Split current region horizontally into two regions.

  • Ctrl+a |: Split current region vertically into two regions.

  • Ctrl+a tab: Switch the input focus to the next region.

  • Ctrl+a Ctrl+a: Toggle between the current and previous windows.

  • Ctrl+a Q: Close all regions but the current one.

  • Ctrl+a X: Close the current region.

7.16.5. Detach from Linux Screen Session

You can detach from the screen session at any time by typing:

Ctrl+a d

The program running in the screen session will continue to run after you detach from the session.

7.16.6. Reattach to a Linux Screen

To resume your screen session use the following command:

screen -r

In case you have multiple screen sessions running on your machine, you will need to append the screen session ID after the r switch.

To find the session ID list the current running screen sessions with:

screen -ls

There are screens on:
    10835.pts-0.linuxize-desktop   (Detached)
    10366.pts-0.linuxize-desktop   (Detached)
2 Sockets in /run/screens/S-linuxize.

If you want to restore screen 10835.pts-0, then type the following command:

screen -r 10835