SSH Crash Course Notes

Introduction to SSH

• SSH stands for Secure Shell.
• It is a protocol used for secure communication between computers.
• Essential for web development, especially when transitioning from FTP.
• This course will cover SSH basics, usage, and key generation.

Overview of SSH Functionality

• Allows for:
  • Creating files on remote computers
  • Running and installing programs
  • Deploying web applications
• SSH is encrypted, providing security compared to protocols like Telnet.
• Commonly used in remote command line or terminal sessions.

Authentication Methods

1. Password Authentication
   • Default method: username/password.
   • Example command: ssh user@hostname
2. SSH Keys
   • Recommended for better security.
   • Involves generating a pair of public and private keys.
3. Host-Based Authentication
   • Uses a known hosts file to manage allowable connections.

Generating SSH Keys

• Use the command: ssh-keygen
  • Default location: ~/.ssh/
  • Files generated:
    • Private Key: id_rsa
    • Public Key: id_rsa.pub
• Public key must be added to the server in the ~/.ssh/authorized_keys file.

Logging into a Local Server

• Example command for logging in: ssh [email protected]
• First-time login prompts to accept the unknown host.
• Upon success, the terminal displays a welcome message.

Managing Files on Remote Servers

• Commands in SSH:
  • ls to list files
  • cd to change directories
  • mkdir to create directories
  • touch to create files
  • rm -rf to remove files/directories.

Installing Software on a Remote Server

• Install Apache as an example:
  • Command: sudo apt install apache2 -y
• Confirm installation by accessing the server's IP address in a web browser.

Setting Up SSH Keys on a Remote DigitalOcean Server

1. Create a Droplet on DigitalOcean:
   • Choose a server package and set up SSH keys.
2. Log in as Root User:
   • Use SSH keys for passwordless entry.
3. Create a New User:
   • Example: adduser username
   • Grant sudo privileges: usermod -aG sudo username

Configuring SSH Key Permissions

• SSH keys must be placed in ~/.ssh/authorized_keys for each user.
• Change ownership of .ssh directory if necessary.
  • Command: sudo chown -R username:username /home/username/.ssh

Setting Up SSH with GitHub

1. Generate a new SSH key specifically for GitHub:
   • Command: ssh-keygen -t rsa -f ~/.ssh/id_rsa_github
2. Add the public key to GitHub under SSH and GPG settings.
3. Clone a repository using the SSH command to confirm functionality.

Additional Commands

• To copy files from local to remote:
  • Use scp command.
• Managing the SSH agent:
  • Start SSH agent using eval $(ssh-agent -s).
  • Add key using ssh-add ~/.ssh/id_rsa_github.

Conclusion

• This crash course provided insights into using SSH, setting up keys, and managing servers.
• Aimed at beginners and those transitioning to remote server management.
• Additional practice with commands and configurations is encouraged for better understanding.