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How To Run Scripts Automatically After SSH Connection on Server

Ubuntu 10

In this article, we will explore the different methods of running scripts automatically after establishing an SSH connection on a server. This can be useful for various tasks like logging, notifications, or performing routine maintenance tasks.

Quick Answer

To run scripts automatically after establishing an SSH connection on a server, you can use the ForceCommand parameter in the SSH server configuration file, the .ssh/rc file on a per-user basis, or the /etc/ssh/sshrc file. These methods allow you to execute scripts for specific users or for every SSH connection.

What is SSH?

SSH, or Secure Shell, is a cryptographic network protocol that allows secure remote login from one computer to another. It is widely used by system administrators for managing systems and applications remotely, allowing them to log into another computer over a network, execute commands and move files from one computer to another.

Running Scripts Automatically After SSH Connection

There are several ways to run scripts automatically after an SSH connection is established. We will discuss three main methods:

  1. Using the ForceCommand parameter in the SSH server configuration file
  2. Using the .ssh/rc file on a per-user basis
  3. Using the /etc/ssh/sshrc file

Method 1: Using the ForceCommand Parameter

The ForceCommand parameter in the SSH server configuration file (/etc/ssh/sshd_config) can be used to execute a specific script every time an SSH connection is established.

Here’s how to do it:

  1. Open the SSH server configuration file in a text editor. For example, you can use nano:
    sudo nano /etc/ssh/sshd_config
  2. Add the ForceCommand parameter and set its value to the path of the script you want to run:
    ForceCommand /usr/bin/ownscript
  3. Save and close the file.
  4. Restart the SSH server to apply the changes:
    sudo systemctl restart ssh

In this method, the script will be executed on the server for every SSH connection, ignoring any command supplied by the client. It’s important to note that you should start a shell in your script file to keep the SSH session open.

Method 2: Using the .ssh/rc File

You can also run scripts on a per-user basis using the .ssh/rc file. Here’s how:

  1. Navigate to the user’s home directory and create a .ssh directory if it doesn’t exist:
    cd ~
    mkdir .ssh
  2. Create an rc file inside the .ssh directory:
    touch .ssh/rc
  3. Open the rc file in a text editor and add the commands you want to run:
    #!/bin/bash
    # Script file for SSH
    #
    # Put your commands here
    echo "test" > /tmp/test.txt
    #
    # Exit by calling a shell to open for the SSH session
    /bin/bash
  4. Make the rc file executable:
    chmod +x .ssh/rc

In this method, the rc file will be executed on the server for that specific user after the SSH connection is established.

Method 3: Using the /etc/ssh/sshrc File

The /etc/ssh/sshrc file can be used to run scripts for every SSH connection. Here’s how:

  1. Create an sshrc file in the /etc/ssh directory:
    sudo touch /etc/ssh/sshrc
  2. Open the sshrc file in a text editor and add the commands you want to run:
    #!/bin/bash
    ip=$(echo $SSH_CONNECTION | cut -d " " -f 1)
    notify-send -u CRITICAL "SSH connection from ${ip}" "User $USER just logged in from $ip"
  3. Make the sshrc file executable:
    sudo chmod +x /etc/ssh/sshrc

In this method, the sshrc file will be executed on the server for every SSH connection.

Conclusion

Running scripts automatically after an SSH connection can be a powerful tool for system administrators. Whether you need to perform specific tasks, log activities, or simply notify when a connection is established, these methods provide a flexible and secure way to automate these processes.

Remember to test your scripts thoroughly to ensure they behave as expected. And always make sure to secure your scripts and SSH configuration files to prevent unauthorized access.

For more information on SSH and scripting, you can visit the OpenSSH documentation.

What is the purpose of running scripts automatically after an SSH connection?

Running scripts automatically after an SSH connection can be useful for tasks like logging activities, sending notifications, or performing routine maintenance tasks on a server.

How do I use the `ForceCommand` parameter to run scripts automatically?

To use the ForceCommand parameter, you need to add it to the SSH server configuration file (/etc/ssh/sshd_config) and set its value to the path of the script you want to run. Remember to start a shell in your script file to keep the SSH session open.

How do I run scripts on a per-user basis using the `.ssh/rc` file?

To run scripts on a per-user basis, you need to create an rc file inside the .ssh directory in the user’s home directory. Add the commands you want to run in the rc file and make it executable using the chmod +x command.

How can I use the `/etc/ssh/sshrc` file to run scripts automatically?

To use the /etc/ssh/sshrc file, you need to create the file in the /etc/ssh directory and add the commands you want to run. Make sure to make the sshrc file executable using the chmod +x command.

What precautions should I take when running scripts automatically after an SSH connection?

It is important to test your scripts thoroughly to ensure they behave as expected. Also, make sure to secure your scripts and SSH configuration files to prevent unauthorized access.

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