Install Windows 3.11

Overview

This skill provides guidance for setting up legacy Windows virtual machines (particularly Windows 3.11) using QEMU with web-based remote access. The core challenge is not just launching the VM, but verifying it reaches a usable state and providing reliable remote access.

Critical Success Criteria

Before marking any VM setup task complete, verify:

1. The VM actually boots to the expected state - Screenshots, VNC connection tests, or QMP display queries must confirm the desktop/expected state
2. Web interface is fully functional - End-to-end test through the browser, not just service status checks
3. Keyboard/mouse input works - Verify input actually affects VM state, not just that commands are accepted

Approach

Phase 1: Environment Assessment

Before installing anything:

1. Check QEMU version requirements in task description - note any specific version compatibility statements
2. Audit existing nginx configuration to understand current server blocks
3. Identify required ports and check for conflicts
4. Determine the disk image format and any special QEMU flags needed

Phase 2: QEMU Configuration

When configuring QEMU for legacy operating systems:

1. Memory allocation: Windows 3.11 typically needs 16-64MB RAM. Check image documentation for requirements
2. VNC setup: Use -vnc :1 for display 1 (port 5901). Consider -vnc :1,share=ignore-disconnects for stability
3. QMP socket: Enable with -qmp unix:/path/to/qmp.sock,server,nowait for programmatic control
4. Display: Legacy OS may need specific display settings like -vga std or -vga cirrus

Example QEMU command structure:

qemu-system-i386 \
  -m 32 \
  -hda /path/to/disk.img \
  -vnc :1 \
  -qmp unix:/tmp/qmp.sock,server,nowait \
  -vga std

Phase 3: Web Access Stack

The typical stack for web-based VNC access:

Browser → nginx (port 80) → websockify → VNC server (QEMU)

nginx configuration approach:

1. First, examine /etc/nginx/nginx.conf for existing server blocks
2. Check if sites-enabled is included in the main config
3. Create configuration in the appropriate location to avoid conflicts
4. Test configuration with nginx -t before reloading

websockify setup:

websockify --web=/usr/share/novnc 6080 localhost:5901

Key parameters:

• --web serves noVNC static files
• Port 6080 is the WebSocket endpoint
• Target is the VNC port (5901 for display :1)

Phase 4: Boot Verification

This is the most commonly failed step. Never assume boot succeeded based on process status alone.

Verification strategies:

1. QMP display query: Send {"execute": "query-status"} to check VM state
2. VNC screenshot: Use vncsnapshot or similar to capture current display
3. QMP screendump: {"execute": "screendump", "arguments": {"filename": "/tmp/screen.ppm"}}
4. Connect via VNC client: Actually view the display, not just test connectivity

Boot timing considerations:

• Legacy OS may need user interaction to complete boot (pressing Enter, clicking OK)
• Implement polling rather than fixed sleep delays
• Consider boot sequence: BIOS → DOS → Windows (multiple stages)

Phase 5: Input Verification

After establishing QMP connection:

1. Send test keystrokes and verify display changes
2. Each QMP connection requires capability negotiation first:

   {"execute": "qmp_capabilities"}
   

3. Then send keys:

   {"execute": "send-key", "arguments": {"keys": [{"type": "qcode", "data": "ret"}]}}
   

Common Pitfalls

QEMU Version Compatibility

If task specifies "compatible with QEMU X.Y.Z" but a different version is installed:

• Document the version mismatch
• Test if the image actually boots with the available version
• Report any compatibility issues observed

nginx Configuration Conflicts

Symptoms: 502 Bad Gateway, connection refused

Prevention:

• Always audit existing nginx config before adding new server blocks
• Check for conflicting listen directives
• Verify upstream (websockify) is running before nginx tries to proxy to it

Premature Task Completion

Never mark "VM booted successfully" without:

• Visual confirmation (screenshot or VNC connection)
• Or QMP state verification showing expected state

QMP Socket Issues

• Stale socket files from previous runs cause connection failures
• Always clean up /tmp/*.sock or equivalent before starting QEMU
• Use socat or nc to test socket connectivity

Boot Detection

Arbitrary sleep commands are unreliable. Instead:

• Poll QMP status at intervals
• Check for specific display content changes
• Implement timeout with failure handling

Verification Checklist

Before declaring task complete:

• QEMU process is running (check with pgrep or ps)
• VNC port is listening (ss -tlnp | grep 5901)
• Websockify is running and connected to VNC
• nginx is proxying correctly (test with curl to WebSocket endpoint)
• Visual confirmation of expected OS state (screenshot or live view)
• Keyboard input affects VM display (send test key, verify change)
• Web interface loads in browser and connects to VM

Resources

references/

Refer to references/qemu_legacy_os.md for detailed QEMU flags and compatibility notes for legacy operating systems.

Refer to references/novnc_nginx_config.md for production-ready nginx configuration templates.