SSH Server Administration

Comprehensive skill for secure remote server management via SSH. Cross-platform compatible: Windows, macOS, and Linux.

Platform Detection

Detect the operating system first to use the correct SSH approach:

• Windows: Use PowerShell or Windows OpenSSH (built into Windows 10+)
• macOS/Linux: Use standard bash SSH commands

Authentication Methods

1. SSH Key Authentication (Recommended)

Check for existing keys:

# Windows (PowerShell)
Get-ChildItem ~/.ssh/id_*.pub

# macOS/Linux
ls -la ~/.ssh/id_*.pub

If keys exist, use them:

ssh -o StrictHostKeyChecking=accept-new [username]@[host] "[command]"

If no keys exist, create them:

# All platforms
ssh-keygen -t ed25519 -C "user@example.com"

# Copy public key to server
ssh-copy-id -i ~/.ssh/id_ed25519.pub [username]@[host]

2. Password Authentication

macOS/Linux with sshpass:

sshpass -p '[password]' ssh -o StrictHostKeyChecking=accept-new [username]@[host] "[command]"

Windows (Python helper):

python scripts/ssh_helper.py --host [host] --user [username] --password [password] --command "[command]"

Credential Collection

When user first requests SSH operation, collect credentials ONCE:

I need SSH connection details:

1. Host/IP Address: (e.g., 192.168.1.100 or server.example.com)
2. Username: (e.g., root, admin, ubuntu)
3. Authentication Method: SSH Key (recommended) or Password
4. Port (optional): Default is 22

Store credentials in working memory for the session. NEVER write to files or logs.

Common Commands

Remote Command Execution

ssh -o StrictHostKeyChecking=accept-new -o ConnectTimeout=30 [username]@[host] "[command]"

File Transfer (SCP)

# Upload file
scp -o StrictHostKeyChecking=accept-new [local_file] [username]@[host]:[remote_path]

# Download file
scp -o StrictHostKeyChecking=accept-new [username]@[host]:[remote_file] [local_path]

Port Forwarding

# Local port forwarding (access remote service locally)
ssh -L [local_port]:localhost:[remote_port] [username]@[host]

# Remote port forwarding (expose local service remotely)
ssh -R [remote_port]:localhost:[local_port] [username]@[host]

# Dynamic SOCKS proxy
ssh -D [local_port] [username]@[host]

Server Administration Tasks

System Information

ssh user@host "uname -a && cat /etc/os-release"  # System info
ssh user@host "df -h"                             # Disk space
ssh user@host "free -h"                           # Memory usage
ssh user@host "ps aux --sort=-%mem | head -20"    # Top processes
ssh user@host "uptime && top -bn1 | head -15"     # System load

Service Management (systemd)

ssh user@host "systemctl status [service_name]"
ssh user@host "sudo systemctl start|stop|restart [service_name]"
ssh user@host "journalctl -u [service_name] -n 50 --no-pager"

Log Analysis

ssh user@host "sudo tail -100 /var/log/syslog"
ssh user@host "sudo grep -i error /var/log/syslog | tail -50"
ssh user@host "sudo tail -50 /var/log/auth.log"

Network Diagnostics

ssh user@host "ss -tulpn"                          # Listening ports
ssh user@host "netstat -an | grep ESTABLISHED"     # Active connections
ssh user@host "ping -c 3 [target] && traceroute [target]"

Configuration Options

Option	SSH Flag	Description
Custom port	-p [port]	Non-standard SSH port
Timeout	-o ConnectTimeout=[sec]	Connection timeout
Compression	-C	Enable compression
Verbose	-v or -vv	Debug output
Identity file	-i [path]	Specific SSH key
Batch mode	-o BatchMode=yes	Fail instead of prompting

Troubleshooting

Issue	Solution
sshpass: command not found (Windows)	Use Python helper or set up SSH keys
sshpass: command not found (macOS)	brew install hudochenkov/sshpass/sshpass
sshpass: command not found (Linux)	apt install sshpass or yum install sshpass
Permission denied	Check username/password/key, verify auth method
Connection refused	Verify host/port, check if SSH service running
Host key changed	Server reinstalled - verify and update known_hosts
Connection timeout	Check network, firewall rules

When to Use This Skill

• "SSH into my server at 192.168.1.100"
• "Connect to my remote machine"
• "Run a command on the server"
• "Upload/download files to/from the server"
• "Set up port forwarding"
• "Create an SSH tunnel"
• "Check server status"
• "Restart a service on the server"
• "View server logs"

When NOT to Use This Skill

• Local file operations (no SSH needed)
• Cloud provider API operations (use their CLIs)
• Database client connections (use database tools)

Security Best Practices

1. Prefer SSH keys over passwords
2. Never echo passwords in command output
3. Use StrictHostKeyChecking appropriately
4. Limit key permissions - chmod 600 ~/.ssh/id_*
5. Use agent forwarding carefully - -A flag