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What is Screen

Screen is a tool found only on Linux and highly useful for server configuration and management by a team. It allows users to create, manage, and detach terminal sessions, which can continue running in the background even if the connection to the server is interrupted. Below is a guide for proper use.

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Installation

On most Linux distributions, screen comes preinstalled. If not, you can install it with:

Service Installation
sudo apt-get install screen  # for Debian/Ubuntu
sudo yum install screen      # for CentOS/RHEL

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Usage

1. Create a new screen session

screen -S name

2. Basic commands:

  1. To detach a screen, use the combination keys of CTRL + A + D

  2. To reattach it, type: screen -r name

  3. To see all active sessions, type:screen -ls

3. Advanced Commands

  1. Move between screens: Ctrl + A then N (next) or P (previous)

  2. Close the current screen: Type exit

  3. Switch to a specific screen within a session: Ctrl + A followed by the window number, e.g., Ctrl + A 0

4. Session Management

  • Save the session output:
screen -L
  • Reattach a specific detached session:
screen -r session_name
  • Terminate a specific session:
screen -X -S session_name quit

To forcefully stop a screen, use screen -X -S session_name kill

5. Forced stop commands

  • End the session using the PID:

  1. Get the PID of the session from the screen list, via screen -ls

  2. Then, type: 

kill -9 PID

Waning: kill -9 is a forced close, so the screen will close immediately, whatever its state (useful in case of a crash), but nothing will be saved upon closing

  • Kill all sessions forcefully:
killall screen

When to use killall screen: This command should be used as a last resort, as it will terminate all active and detached screen sessions for all users on the system. It’s best used when screens are unresponsive or left open by mistake, especially if you have administrative rights and need to close lingering sessions.

Warning: Use forced shutdown commands with caution. Terminating screen sessions abruptly may cause data loss, interrupt applications, or corrupt files, especially if critical processes are running. Always try quit first to allow programs to exit gracefully, and reserve forced termination for unresponsive sessions only.

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