Configure SSH in PuTTY

• Double-click putty.exe to open the PuTTY Configuration window
• You'll see the Session category selected by default
• This is where you'll configure your basic connection settings

In the "Host Name (or IP address)" field, enter one of:

• Domain name: example.com
• Subdomain: server.example.com
• IPv4 address: 192.168.1.100
• IPv6 address: 2001:db8::1

Port Configuration:

• Default SSH port: 22
• Custom port: If your server uses a non-standard port (e.g., 2222), enter it here
• The port number is displayed to the right of the hostname field

Connection Type:

• Select "SSH" from the connection type options
• Other options: Raw, Telnet, Rlogin, Serial (not commonly used)
• SSH is the most secure option and should be used for remote connections

To avoid typing your username each time:

1. In the left panel, navigate to Connection → Data
2. Find the "Auto-login username" field
3. Enter your SSH username (e.g., root, admin, ubuntu)
4. PuTTY will automatically use this username when connecting

Save your configuration for easy access:

1. Return to the Session category (top of left panel)
2. In the "Saved Sessions" field, enter a descriptive name:
   • Production Web Server
   • Dev Database - MySQL
   • Client XYZ - Main
3. Click the "Save" button
4. Your session now appears in the list below

1. Click the "Open" button at the bottom of the window
2. If this is your first connection to this server, you'll see a security alert
3. Click "Accept" to trust the server's host key
4. A terminal window opens
5. Enter your password when prompted (if using password authentication)

1. Open your saved session or create a new one
2. In the left panel, navigate to:
   Connection → SSH → Auth → Credentials
3. Click "Browse" next to "Private key file for authentication"
4. Select your .ppk private key file
5. Return to Session and click "Save" to update
6. Click "Open" to connect
7. Enter your key passphrase if you set one

1. Navigate to Connection
2. Set "Seconds between keepalives" to 60
3. Enable "Enable TCP keepalives (SO_KEEPALIVE option)"
4. This sends periodic packets to keep the connection alive

1. Navigate to Connection → SSH
2. Under "Protocol options", select SSH protocol version 2 only
3. SSH-2 is more secure and should always be used
4. SSH-1 is obsolete and vulnerable

For slow connections, enable compression:

1. Navigate to Connection → SSH
2. Enable "Enable compression"
3. Useful for high-latency or low-bandwidth connections
4. May slightly increase CPU usage

Run graphical applications remotely:

1. Navigate to Connection → SSH → X11
2. Enable "Enable X11 forwarding"
3. Requires an X server on Windows (e.g., Xming, VcXsrv)
4. GUI apps will display on your Windows desktop

Possible causes:

• SSH service not running on the server
• Firewall blocking port 22
• Wrong port number
• Server is down

Solutions:

1. Verify the server is online: ping hostname
2. Check if SSH service is running on the server
3. Verify the correct port number
4. Check firewall rules (both client and server)

Possible causes:

• Network connectivity issues
• Firewall blocking connection
• Incorrect hostname/IP
• Server not responding

Solutions:

1. Verify internet connection
2. Check if hostname resolves: nslookup hostname
3. Try alternative network (mobile hotspot, VPN)
4. Contact server administrator

Possible causes:

• Public key not added to server's authorized_keys
• Wrong private key selected
• File permissions incorrect on server
• Server doesn't allow public key authentication

Solutions:

1. Verify public key is in ~/.ssh/authorized_keys on server
2. Check file permissions: ~/.ssh/ should be 700, authorized_keys should be 600
3. Try password authentication to diagnose
4. Check server's /etc/ssh/sshd_config for PubkeyAuthentication yes

Possible causes:

• Wrong username
• Wrong password
• Account locked or disabled
• IP address blocked by fail2ban or similar

Solutions:

1. Double-check username and password
2. Verify account is active on the server
3. Contact server administrator to check for IP blocks
4. Wait 10-15 minutes if locked by brute-force protection

Possible causes:

• Server's host key has changed (reinstalled OS, new server)
• Man-in-the-middle attack (rare)
• Cached old host key in PuTTY

Solutions:

1. If you know the server was rebuilt, this is expected
2. In PuTTY, click "Update" to accept the new key
3. Or manually delete old key from Windows Registry:
   HKEY_CURRENT_USER\Software\SimonTatham\PuTTY\SshHostKeys
4. If unexpected, contact your server administrator before proceeding

Export your PuTTY sessions for backup:

1. Open Registry Editor (regedit)
2. Navigate to: HKEY_CURRENT_USER\Software\SimonTatham\PuTTY\Sessions
3. Right-click "Sessions" → Export
4. Save as putty-sessions-backup.reg
5. To restore: Double-click the .reg file