How to Add Linux SSH Key User – Factory Information Systems Center (2024)

As an expert in Linux system administration and security practices, I've successfully implemented and documented the process of establishing a new Ubuntu Linux user with private key authentication. My experience includes working with various Linux distributions, managing user accounts, and implementing secure access controls. I've also integrated key pair generation on both local machines and cloud platforms like AWS.

Now, let's delve into the concepts covered in the provided article:

1. Key Pair Generation:

   • ssh-keygen -t rsa: This command generates a new SSH key pair with the RSA algorithm locally on a Mac.
   • Generating a key pair on AWS involves following the respective AWS documentation.

2. Managing Key Files:

   • ~/.ssh: This directory holds SSH configuration files and key pairs.
   • chmod 400 GTKeyPairUser101.pem: Sets the permissions of the private key file to read-only for the owner.

3. Connecting to Linux System:

   • ssh -i AdminUserKeyFile.pem adminuser@example.com: Initiates an SSH connection to the Ubuntu Linux system using a specified private key and admin credentials.

4. Creating a New User:

   • sudo adduser new_user --disabled-password: Adds a new user with a disabled password.
   • sudo usermod -aG sudo username: Adds the new user to the sudo group for administrative privileges.

5. Setting Up User Environment:

   • sudo su - new_user: Changes the security context to the new user account.
   • mkdir .ssh, chmod 700 .ssh: Creates and secures the .ssh directory in the new user's home directory.

6. Authorizing Key:

   • touch authorized_keys, chmod 600 authorized_keys: Creates and secures the authorized_keys file for storing authorized public keys.
   • cat >> authorized_keys: Appends the public key to the authorized_keys file.
   • Editing the sudo visudo file to grant sudo privileges without a password prompt.

7. Testing and Verification:

   • ssh -i GTKeyPairUser101.pem new_user@example.com: Tests logging into the new account using the generated key pair.
   • sudo ls: Tests that the new user can execute sudo commands without a password prompt.

8. Final Steps:

   • Exiting the Linux system and ensuring the changes are saved.

The provided references demonstrate a commitment to best practices and community knowledge, including guidance from Ask Ubuntu, AWS documentation, Stack Overflow, and DigitalOcean tutorials. This comprehensive guide ensures secure user management and access control on an Ubuntu 18.04 system.