Linux SSH Configuration

Linux SSH Configuration Guide

Complete beginner-friendly guide to SSH configuration on Linux, covering Arch Linux, CachyOS, and other distributions including server setup, client configuration, key-based authentication, and security hardening.

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Table of Contents

1. Installing SSH
2. SSH Server Configuration
3. SSH Client Configuration
4. Key-Based Authentication
5. SSH Security
6. Troubleshooting

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Installing SSH

Install OpenSSH

Install SSH:

# Arch/CachyOS
sudo pacman -S openssh

# Debian/Ubuntu
sudo apt install openssh-server

# Fedora
sudo dnf install openssh-server

Enable SSH

Enable service:

# Enable service
sudo systemctl enable --now sshd.service

# Check status
systemctl status sshd

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SSH Server Configuration

Configure SSH Server

Edit config:

# Edit SSH config
sudo vim /etc/ssh/sshd_config

Security settings:

# Disable root login
PermitRootLogin no

# Change port
Port 2222

# Disable password auth (use keys)
PasswordAuthentication no

# Allow specific users
AllowUsers username

# Disable empty passwords
PermitEmptyPasswords no

Restart SSH:

sudo systemctl restart sshd

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SSH Client Configuration

SSH Client Config

Edit client config:

# Edit config
vim ~/.ssh/config

Example:

Host myserver
    HostName server.example.com
    User username
    Port 2222
    IdentityFile ~/.ssh/id_rsa

Connect

Connect to server:

# Basic connection
ssh user@server

# With config
ssh myserver

# With key
ssh -i ~/.ssh/key user@server

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Key-Based Authentication

Generate Key

Create SSH key:

# Generate key
ssh-keygen -t ed25519 -C "your_email@example.com"

# Or RSA
ssh-keygen -t rsa -b 4096

Copy Key

Copy to server:

# Copy key
ssh-copy-id user@server

# Or manually
cat ~/.ssh/id_rsa.pub | ssh user@server "mkdir -p ~/.ssh && cat >> ~/.ssh/authorized_keys"

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SSH Security

Harden SSH

Security settings:

# Edit config
sudo vim /etc/ssh/sshd_config

Add:

PermitRootLogin no
PasswordAuthentication no
PubkeyAuthentication yes
MaxAuthTries 3

fail2ban

Install fail2ban:

# Install fail2ban
sudo pacman -S fail2ban

# Enable
sudo systemctl enable fail2ban
sudo systemctl start fail2ban

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Troubleshooting

Cannot Connect

Check service:

# Check SSH status
systemctl status sshd

# Check firewall
sudo ufw status

Permission Denied

Check permissions:

# Check key permissions
chmod 600 ~/.ssh/id_rsa
chmod 644 ~/.ssh/id_rsa.pub
chmod 700 ~/.ssh

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Summary

This guide covered SSH configuration for Arch Linux, CachyOS, and other distributions, including server setup, client configuration, and security.

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Next Steps

• Security Configuration - Security setup
• Remote Desktop - Remote access
• System Hardening - System hardening
• ArchWiki SSH: https://wiki.archlinux.org/title/OpenSSH

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This guide covers Arch Linux, CachyOS, and other Linux distributions. For distribution-specific details, refer to your distribution's documentation.