How To Use Linux Screen in Linux

When you perform a long-running task on a remote machine, and suddenly your connection drops, the SSH session is terminated, and your work is lost。Don't worry, there is a utility called screen that allows us to resume the sessions.

What is screen?

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.

Install Screen

The screen soft package is pre-installed on most Linux distros. You can check it typing the following command:

screen --version

If you don't have screen installed on your system, you can easily install it using the package manager of your distro.

sudo apt install screen # ubunt and debian
sudo yum install screen # CentOs and Fedora

How to use 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 ?

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.

Working with 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.

o 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 window
  • 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 region
  • Ctrl+a Q Close all regions but the current one
  • Ctrl+a X Close the current region

Detach from 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.

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.linuxhowto-desktop   (Detached)
    10366.pts-0.linuxhowto-desktop   (Detached)
2 Sockets in /run/screens/S-linuxhowto.

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

screen -r 10835

Customize Linux Screen

When screen is started, it reads its configuration parameters from /etc/screenrc and ~/.screenrc if the file is present. We can modify the default Screen settings according to our preferences using the .screenrc file.

Here is a sample ~/.screenrc configuration with customized status line and few additional options:

# Turn off the welcome message
startup_message off

# Disable visual bell
vbell off

# Set scrollback buffer to 10000
defscrollback 10000

# Customize the status line
hardstatus alwayslastline
hardstatus string '%{= kG}[ %{G}%H %{g}][%= %{= kw}%?%-Lw%?%{r}(%{W}%n*%f%t%?(%u)%?%{r})%{w}%?%+Lw%?%?%= %{g}][%{B} %m-%d %{W}%c %{g}]'

Below are the most basic steps for getting started with screen:

  1. On the command prompt, type screen.
  2. Run the desired program.
  3. Use the key sequence Ctrl-a + Ctrl-d to detach from the screen session.
  4. Reattach to the screen session by typing screen -r.

Conclusion

In this tutorial, you have learned how to use Gnu Screen. Now you can start using the Screen utility and create multiple screen windows from a single session.

There's lots more to learn about GNU Screen at Screen User's Manual page.

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