Headless Windows 11 VM Skill

Headless Windows 11 VM

Manage a headless Windows 11 VM running via dockur/windows in Docker with KVM acceleration. The VM is accessible via SSH only — no RDP or GUI required.

Host prerequisites

Docker
KVM support (/dev/kvm must exist — check with ls /dev/kvm)
sshpass (sudo apt install sshpass)
imagemagick (optional, for screenshot debugging: sudo apt install imagemagick)

Configuration

Container name: windows11
VM directory: $HOME/windows-vm/
- storage/ — VM disk image (managed by dockur, wiped on recreate)
- iso/win11x64.iso — cached Windows ISO (7.3GB, persists across recreates)
- oem/install.bat — post-install script (installs OpenSSH Server)
Credentials: user / password
SSH: localhost:2222 (bound to 127.0.0.1 only)
RDP: localhost:3389 (bound to 127.0.0.1 only, fallback)
Web console: localhost:8006 (VNC in browser, for debugging)
Resources: 8GB RAM, 4 CPU cores, 64GB disk

Actions

create — First-time setup or full recreate

Ensure directories exist:

mkdir -p "$HOME/windows-vm/oem" "$HOME/windows-vm/storage" "$HOME/windows-vm/iso"

Ensure $HOME/windows-vm/oem/install.bat exists with OpenSSH setup:

@echo off
echo Installing OpenSSH Server...
powershell -Command "Add-WindowsCapability -Online -Name OpenSSH.Server~~~~0.0.1.0" 2>nul
powershell -Command "Get-WindowsCapability -Online -Name OpenSSH.Server* | Add-WindowsCapability -Online" 2>nul
dism /Online /Add-Capability /CapabilityName:OpenSSH.Server~~~~0.0.1.0 2>nul
powershell -Command "Start-Service sshd" 2>nul
powershell -Command "Set-Service -Name sshd -StartupType Automatic"
powershell -Command "New-ItemProperty -Path 'HKLM:\SOFTWARE\OpenSSH' -Name DefaultShell -Value 'C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe' -PropertyType String -Force"
powershell -Command "New-NetFirewallRule -Name 'OpenSSH-Server' -DisplayName 'OpenSSH Server' -Enabled True -Direction Inbound -Protocol TCP -Action Allow -LocalPort 22"
powershell -Command "Get-Service sshd" 2>nul
echo Done.

If recreating, remove the old container and disk:

docker stop windows11 && docker rm windows11
rm -f "$HOME/windows-vm/storage/data.img"

Launch the container. There are two cases:

If cached ISO exists ($HOME/windows-vm/iso/win11x64.iso):

docker run -d \
  --name windows11 \
  -p 127.0.0.1:3389:3389 \
  -p 127.0.0.1:2222:22 \
  -p 127.0.0.1:8006:8006 \
  -e RAM_SIZE="8G" \
  -e CPU_CORES="4" \
  -e DISK_SIZE="64G" \
  -e USERNAME="user" \
  -e PASSWORD="password" \
  --cap-add NET_ADMIN \
  --device /dev/kvm \
  -v "$HOME/windows-vm/storage:/storage" \
  -v "$HOME/windows-vm/oem:/oem" \
  -v "$HOME/windows-vm/iso/win11x64.iso:/boot.iso" \
  dockurr/windows

First time (no cached ISO) — omit the /boot.iso mount and add VERSION:

docker run -d \
  --name windows11 \
  -p 127.0.0.1:3389:3389 \
  -p 127.0.0.1:2222:22 \
  -p 127.0.0.1:8006:8006 \
  -e RAM_SIZE="8G" \
  -e CPU_CORES="4" \
  -e DISK_SIZE="64G" \
  -e VERSION="win11" \
  -e USERNAME="user" \
  -e PASSWORD="password" \
  --cap-add NET_ADMIN \
  --device /dev/kvm \
  -v "$HOME/windows-vm/storage:/storage" \
  -v "$HOME/windows-vm/oem:/oem" \
  dockurr/windows

After the ISO downloads and Windows boots, immediately copy the ISO out before the container is ever stopped (dockur wipes /storage on recreate):

cp "$HOME/windows-vm/storage/win11x64.iso" "$HOME/windows-vm/iso/win11x64.iso"

Wait for Windows install + OpenSSH setup to complete. This takes 20-30 minutes for a fresh install (the OEM install.bat runs at the end of Windows OOBE and downloads OpenSSH from Microsoft, which is slow). Monitor with:
```
docker logs -f windows11
```
You can also watch the VM screen via the web console at http://localhost:8006.

To check if SSH is up:
```
sshpass -p 'password' ssh -o StrictHostKeyChecking=no -o ConnectTimeout=5 -p 2222 user@localhost "whoami"
```

Once SSH is responding, install Node.js and Claude Code by piping a setup script via stdin (avoids PowerShell escaping hell over SSH):

cat << 'PS' | sshpass -p 'password' ssh -o StrictHostKeyChecking=no -p 2222 user@localhost "powershell -ExecutionPolicy Bypass -Command -"
# Download and install Node.js silently
Invoke-WebRequest -Uri 'https://nodejs.org/dist/v22.14.0/node-v22.14.0-x64.msi' -OutFile 'C:\Users\user\node-install.msi'
Start-Process msiexec.exe -ArgumentList '/i C:\Users\user\node-install.msi /qn /norestart' -Wait -Verb RunAs
Write-Host "Node.js installed"

# Install Claude Code globally
& 'C:\Program Files\nodejs\npm.cmd' install -g @anthropic-ai/claude-code
Write-Host "Claude Code installed"

# Add npm global bin to SYSTEM PATH (user PATH is not read by sshd)
$systemPath = [Environment]::GetEnvironmentVariable('Path', 'Machine')
$additions = @()
if ($systemPath -notlike '*AppData*npm*') { $additions += 'C:\Users\user\AppData\Roaming\npm' }
if ($systemPath -notlike '*Git\cmd*') { $additions += 'C:\Program Files\Git\cmd' }
if ($additions.Count -gt 0) {
    [Environment]::SetEnvironmentVariable('Path', $systemPath + ';' + ($additions -join ';'), 'Machine')
    Write-Host "Added to system PATH: $($additions -join ', ')"
}

# Set execution policy machine-wide (required for claude.ps1)
Set-ExecutionPolicy RemoteSigned -Scope LocalMachine -Force -ErrorAction SilentlyContinue

# Create system-wide PowerShell profile that rebuilds PATH from registry on login.
# Without this, interactive SSH sessions don't pick up the full system PATH.
$profileDir = Split-Path $PROFILE.AllUsersAllHosts
if (-not (Test-Path $profileDir)) { New-Item -ItemType Directory -Path $profileDir -Force }
@'
$machinePath = [Environment]::GetEnvironmentVariable('Path', 'Machine')
$userPath = [Environment]::GetEnvironmentVariable('Path', 'User')
$env:Path = "$machinePath;$userPath"
'@ | Set-Content -Path $PROFILE.AllUsersAllHosts -Force
Write-Host "PowerShell profile created"

# Restart sshd so it picks up the new PATH
Restart-Service sshd -Force
PS

Note: the connection will drop when sshd restarts — that's expected.

Clear the stale host key (new VM = new host key) and verify:

ssh-keygen -f ~/.ssh/known_hosts -R '[localhost]:2222'
sshpass -p 'password' ssh -o StrictHostKeyChecking=no -p 2222 user@localhost "claude --version"

start — Start a stopped VM

docker start windows11

stop — Stop the VM

docker stop windows11

restart — Restart the VM

docker restart windows11

status — Check VM status

docker ps -f name=windows11 --format "table {{.Status}}\t{{.Ports}}"
docker logs windows11 2>&1 | tail -5

ssh — Connect to the VM

ssh -p 2222 user@localhost

screenshot — See what's on the VM screen (for debugging)

docker exec windows11 bash -c "echo 'screendump /tmp/screen.ppm' | nc -w 2 localhost 7100" > /dev/null 2>&1
sleep 1
docker cp windows11:/tmp/screen.ppm /tmp/screen.ppm
convert /tmp/screen.ppm /tmp/screen.png

Important Notes

ISO caching: The /storage volume is managed by dockur and gets wiped on recreate. Store the ISO separately in $HOME/windows-vm/iso/ and mount it as /boot.iso to skip the 7.3GB download.
--cap-add NET_ADMIN is required for port forwarding to work. Without it, QEMU falls back to user-mode networking and port forwarding silently fails.
--device /dev/kvm is required for hardware acceleration.
Boot time: Fresh install takes 20-30 min (Windows install + OpenSSH download from Microsoft). Subsequent boots from existing data.img are fast (~2 min).
Ports are bound to 127.0.0.1 only — not exposed to the network.
Do NOT use -e VERSION="win11" when mounting /boot.iso — the version is auto-detected from the ISO.

Post-install gotchas

Node.js is not pre-installed — the Claude Code install script (irm https://claude.ai/install.ps1 | iex) will report success but claude won't work without Node. Install Node.js via MSI first.
npm global bin not in PATH — Node's MSI adds C:\Program Files\nodejs to PATH but not C:\Users\user\AppData\Roaming\npm (where npm install -g puts binaries). Must add it to the system PATH (not user PATH) because OpenSSH's sshd only reads system PATH. After changing system PATH, restart sshd.
PowerShell execution policy — Default policy is Restricted, which blocks claude.ps1. Must set to RemoteSigned at LocalMachine scope (not CurrentUser) for it to take effect in SSH sessions.
Escaping hell — Running PowerShell commands over SSH with nested quotes is unreliable. Pipe scripts via stdin using powershell -ExecutionPolicy Bypass -Command - instead.
Interactive SSH sessions don't get full PATH — Windows OpenSSH sshd doesn't properly propagate the system PATH to interactive PowerShell sessions. Fix: create a system-wide PowerShell profile ($PROFILE.AllUsersAllHosts) that rebuilds $env:Path from the registry on every login.
winget may not work — The Microsoft Store certificate can fail in a VM. Use direct MSI/installer downloads instead.
Host key changes — Each recreated VM gets new SSH host keys. Run ssh-keygen -R '[localhost]:2222' to clear the old one.

Agent Skills: Headless Windows 11 VM

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