SSH (Secure Shell)¶

Introduction¶

• SSH, short for Secure Shell, is a cryptographic network protocol used for secure communication over an unsecured network.
• It allows users to securely access and control remote systems over an encrypted connection. In this tutorial, we'll cover the basics of SSH, including how to set it up, connect to remote servers, and perform common tasks.

SSH Key Generation¶

SSH keys are a pair of cryptographic keys used to authenticate and establish a secure connection between two computers. Follow these steps to generate SSH keys:

# Generate SSH key pair
ssh-keygen -t rsa -b 4096 -C "your_email@example.com"

This command will create a public key (id_rsa.pub) and a private key (id_rsa) in the ~/.ssh/ directory by default. -c "your_email@example.com" is the comment to the key

Common SSH Commands¶

Here are some common SSH commands:

• ssh: Connect to a remote server.

  ssh username@remote_host
  ## Example
  ssh john@example.com
  

• scp: Securely copy files between local and remote systems.

  scp source_file username@remote_host:destination_file
  ## Example
  scp /path/to/local/file.txt john@example.com:/path/to/remote/directory/file.txt
  

• sftp: Securely transfer files between local and remote systems.

  sftp username@remote_host
  ## Example
  sftp john@example.com
  

• ssh-keygen: Generate SSH key pairs.

  ssh-keygen -t rsa -b 4096 -C "your_email@example.com"
  ## Example
  ssh-keygen -t rsa -b 4096 -C "john@example.com"
  

• ssh-add: Add SSH private keys to the SSH authentication agent.

  ssh-add /path/to/private_key
  ## Example
  ssh-add ~/.ssh/id_rsa
  

• ssh-copy-id: Copy your public SSH key to a remote server's authorized_keys file.

  ssh-copy-id username@remote_host
  ## Example
  ssh-copy-id john@example.com
  

• exit: close the current connection

Connecting to a Remote Server¶

To connect to a remote server using SSH, you'll need the server's IP address or domain name and your SSH credentials. Use the following command:

ssh username@remote_host

Replace username with your username on the remote server and remote_host with the server's IP address or domain name.

Connects Server using Public & Private keys¶

1. Generate pair of keys using ssh-keygen
2. Copy the public SSH key to the server using ssh-copy-id username@remote_host
3. Connect Server without password verify using ssh username@remote_host

SSH Configuration¶

SSH configurations are stored in the ~/.ssh/config file. You can customize SSH behavior by modifying this file.

Here's an example configuration [The default Port for SSH is 22]:

Host example
    HostName example.com
    User username
    Port 22
    IdentityFile ~/.ssh/id_rsa

This configuration allows you to connect to the remote server by typing ssh example.

Host gitlab.com
	Hostname gitlab.com
	User git
	PreferredAuthentications publickey
	IdentityFile ~/.ssh/gitlab