How to Enable and Configure SSH on Linux, Windows, and macOS

Quick Answer: Ubuntu/Debian: sudo apt install openssh-server -y && sudo systemctl enable --now ssh. CentOS: sudo dnf install openssh-server -y && sudo systemctl enable --now sshd. Then connect: ssh user@ip-address.

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Linux: Ubuntu/Debian

Install and Enable

# Install OpenSSH server
sudo apt update
sudo apt install openssh-server -y

# Start and enable (auto-start on boot)
sudo systemctl enable --now ssh

# Check status
sudo systemctl status ssh

Allow Through Firewall

# UFW (Ubuntu's default firewall)
sudo ufw allow ssh
# or specifically:
sudo ufw allow 22/tcp

# Check firewall status
sudo ufw status

Test Connection

From another computer:

ssh your-username@your-server-ip
# Example:
ssh [email protected]

Linux: CentOS/RHEL/Fedora

# Install
sudo dnf install openssh-server -y

# Start and enable
sudo systemctl enable --now sshd

# Check status
sudo systemctl status sshd

# Allow through firewall
sudo firewall-cmd --permanent --add-service=ssh
sudo firewall-cmd --reload

Linux: Arch

sudo pacman -S openssh
sudo systemctl enable --now sshd

Windows 11/10

Enable OpenSSH Server

Open Settings → System → Optional Features
Click Add a feature
Search for OpenSSH Server
Click Install

Or via PowerShell (admin):

# Install OpenSSH Server
Add-WindowsCapability -Online -Name OpenSSH.Server~~~~0.0.1.0

# Start the service
Start-Service sshd

# Set to auto-start on boot
Set-Service -Name sshd -StartupType 'Automatic'

# Allow through Windows Firewall (usually auto-added)
New-NetFirewallRule -Name sshd -DisplayName 'OpenSSH Server' -Enabled True -Direction Inbound -Protocol TCP -Action Allow -LocalPort 22

Connect to Windows

# From another machine
ssh your-windows-username@your-windows-ip

Default shell is Command Prompt. To use PowerShell:

# On the Windows server, set default shell to PowerShell
New-ItemProperty -Path "HKLM:\SOFTWARE\OpenSSH" -Name DefaultShell -Value "C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe" -PropertyType String -Force

macOS

macOS has SSH client built-in. To enable the SSH server (Remote Login):

Via System Settings

Open System Settings → General → Sharing
Toggle Remote Login on
Choose "All users" or specific users

Via Terminal

# Enable
sudo systemsetup -setremotelogin on

# Disable
sudo systemsetup -setremotelogin off

# Check status
sudo systemsetup -getremotelogin

Configure SSH Server

The config file is /etc/ssh/sshd_config:

sudo nano /etc/ssh/sshd_config

Common Settings

# Change SSH port (default: 22)
Port 2222

# Disable root login
PermitRootLogin no

# Disable password authentication (key-only)
PasswordAuthentication no

# Allow specific users only
AllowUsers sam admin

# Set max authentication attempts
MaxAuthTries 3

# Idle timeout (disconnect after inactivity)
ClientAliveInterval 300
ClientAliveCountMax 2

After changes:

# Test config for errors
sudo sshd -t

# Restart SSH
sudo systemctl restart ssh     # Ubuntu/Debian
sudo systemctl restart sshd    # CentOS/RHEL

Set Up SSH Keys (Key-Based Authentication)

Password login is insecure. Set up SSH keys:

On Your Local Machine

# Generate a key pair
ssh-keygen -t ed25519

# Copy your public key to the server
ssh-copy-id [email protected]

# Now connect without password
ssh [email protected]

Then Disable Password Login

# On the server
sudo nano /etc/ssh/sshd_config

PasswordAuthentication no

sudo systemctl restart ssh

Full guide: SSH Keys Setup

Find Your IP Address

# Linux — local IP
ip addr show | grep "inet " | grep -v 127.0.0.1

# Linux — public IP
curl ifconfig.me

# Windows
ipconfig

# macOS
ifconfig | grep "inet " | grep -v 127.0.0.1

Or use our tool: What's My IP

Troubleshooting

# Check if SSH is running
sudo systemctl status ssh     # Ubuntu
sudo systemctl status sshd    # CentOS

# Check if SSH is listening
ss -tlnp | grep :22

# Test connection with verbose output
ssh -v [email protected]

# Check SSH logs
sudo journalctl -u ssh -f         # Ubuntu
sudo journalctl -u sshd -f        # CentOS
sudo tail -f /var/log/auth.log     # Ubuntu
sudo tail -f /var/log/secure       # CentOS

Problem	Fix
`Connection refused`	SSH not running. Install and start it
`Connection timed out`	Firewall blocking port 22. Open it
`Permission denied (publickey)`	Server requires keys. Set up SSH keys
`Permission denied (password)`	Wrong password, or password auth disabled
`Host key verification failed`	Server reinstalled. Run `ssh-keygen -R hostname`
Port 22 blocked by ISP/network	Change SSH to port 443 or 2222
Can SSH locally but not remotely	Firewall, NAT, or ISP blocking. Check port forwarding

Check if Port 22 is Open

# From another machine
nc -zv 192.168.1.100 22
# or use our tool: Port Scanner at /tools/port-scanner/

Related Guides

SSH Cheat Sheet — every SSH command
SSH Keys Setup — key-based authentication
How to Secure SSH — hardening guide
SSH Config Guide — config file mastery
Complete SSH Guide — comprehensive reference
Fail2ban Setup — brute-force protection
UFW Cheat Sheet — firewall management
VPS Setup Guide — first server setup

Related Tools

Port Scanner — check if SSH port is open
What's My IP — find your IP address