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SSH Configuration

Installation and Configuration

Basic Setup

# Install SSH server
sudo apt update
sudo apt install openssh-server

# Enable SSH service
sudo systemctl enable ssh

Restrict SSH to Local IP

# Edit SSH configuration
sudo nano /etc/ssh/sshd_config

# Add or modify the following line
ListenAddress 192.168.1.100  # Replace with your local IP

# Restart the service
sudo systemctl restart ssh

Connect to SSH Server

ssh username@server_ip_address

Security Enhancements

Two-Factor Authentication with Google Authenticator

  1. Install Google Authenticator:
sudo apt-get update
sudo apt-get install libpam-google-authenticator
  1. Run the setup:
google-authenticator
  1. Configure PAM:
# Edit PAM configuration
sudo nano /etc/pam.d/sshd

# Add at the top of the file
auth required pam_google_authenticator.so
  1. Update SSH configuration:
# Edit SSH configuration
sudo nano /etc/ssh/sshd_config

# Set the following options
ChallengeResponseAuthentication yes
UsePAM yes
KbdInteractiveAuthentication yes
  1. Apply changes:
sudo systemctl restart ssh

Restrict or Disable SSH

Restrict SSH to Localhost Only

# Edit SSH configuration
sudo nano /etc/ssh/sshd_config

# Set listening address to localhost
ListenAddress 127.0.0.1

# Restart service
sudo systemctl restart ssh

Stop SSH Service

# Stop the service
sudo systemctl stop ssh

# Disable automatic startup (optional)
sudo systemctl disable ssh

# Verify status
sudo systemctl status ssh

Completely Disable SSH

# Stop and disable both service and socket
sudo systemctl stop ssh.socket
sudo systemctl disable ssh.socket