Windows Sandbox

A Windows sandbox runs a Windows guest in a Linux container via KVM/QEMU and is managed end-to-end through the OpenSandbox lifecycle API (create, expose endpoints, delete). The current Windows profile is based on dockur/windows, with service integration and capabilities provided by OpenSandbox.

Scope

This guide covers the OpenSandbox Server Windows profile (platform.os=windows):

• Create a Windows sandbox
• Check status and endpoints
• Common resources and volume settings
• Delete and cleanup

How it works

• Runtime: dockur/windows runs the Windows guest in a Linux container (requires KVM/QEMU), using mount points such as /storage and /boot.iso for the system disk and install media.
• Control plane: On create, OpenSandbox Server injects the Windows profile configuration (devices, capabilities, execd, port mappings) and enforces resource checks, state, and endpoint publication.
• Client: You call the Lifecycle API or the Python SDK with platform.os=windows, then follow create → poll Running → get endpoints → use → delete.

Prerequisites

• Reachable OpenSandbox Server (e.g. http://localhost:8080)
• Host meets the Windows profile requirements:
  • /dev/kvm present
  • /dev/net/tun present
• Server storage.allowed_host_paths configured for allowed host paths
• A host directory to bind to /storage (recommended)
• Optional: a local Windows ISO for /boot.iso (cuts repeated download time)

Key settings and constraints

Platform and image

• Set platform: {"os":"windows","arch":"amd64"} (arm64 depends on the host)
• Suggested image: dockurr/windows:latest; see dockur/windows releases and Docker Hub tags

Minimum resources

The Windows profile enforces:

• resourceLimits.cpu >= 2
• resourceLimits.memory >= 4G
• resourceLimits.disk >= 64G

resourceLimits vs. environment variables

If resourceLimits is set, the server maps it to and overwrites these env vars:

• CPU_CORES
• RAM_SIZE
• DISK_SIZE

Prefer resourceLimits only; do not set those three env vars manually.

Default ports and USER_PORTS

The Windows profile wires these ports by default:

• 44772 (execd)
• 8080
• 3389/tcp, 3389/udp (RDP)
• 8006/tcp (typical web console)

It also builds or merges USER_PORTS (often 44772,8080,3389,8006).

Storage mounts

• Bind a writable host directory to /storage
• Optional: bind an ISO file to /boot.iso (readOnly=true)
• Host paths must fall under storage.allowed_host_paths or the request is rejected

End-to-end example (Python)

This flow:

1. Create a Windows sandbox
2. Wait until Running
3. Get the 44772 endpoint
4. Use the Python SDK against the sandbox
5. Delete the sandbox

Minimal example

import os
from datetime import timedelta

from opensandbox import SandboxSync
from opensandbox.config import ConnectionConfigSync
from opensandbox.models.sandboxes import PlatformSpec

BASE_URL = os.getenv("OPEN_SANDBOX_BASE_URL", "http://localhost:8080")
API_KEY = os.getenv("OPEN_SANDBOX_API_KEY", "")


def main() -> None:
    cfg = ConnectionConfigSync(
        domain=BASE_URL,
        api_key=API_KEY or None,
        use_server_proxy=True,
    )

    sbx = None
    try:
        sbx = SandboxSync.create(
            image="dockurr/windows:latest",
            timeout=timedelta(hours=12),
            ready_timeout=timedelta(minutes=30),
            resource={
                "cpu": "4",
                "memory": "8G",
                "disk": "64G",
            },
            env={"VERSION": "11"},
            entrypoint=["cmd", "/c", "echo OpenSandbox Windows profile"],
            platform=PlatformSpec(os="windows", arch="amd64"),
            connection_config=cfg,
        )
        print("created:", sbx.id)

        endpoint = sbx.get_endpoint(44772)
        print("execd endpoint:", endpoint.endpoint)
        print("sdk health:", sbx.is_healthy())
    finally:
        if sbx is not None:
            try:
                sbx.kill()
                print("deleted:", sbx.id)
            finally:
                sbx.close()


if __name__ == "__main__":
    main()

The sample keeps SDK health waiting (ready_timeout=30m). Windows cold start can be slow; increase ready_timeout as needed. For custom readiness logic, use skip_health_check=True and poll for Running in your app.

Advanced options

Persistent /storage

Bind a host path to /storage for a persistent system/user data directory. The directory need not exist ahead of time: it may be created on bind mount (fresh), or reused if it already exists. host.path must still be under an allowed storage.allowed_host_paths prefix, regardless of whether the directory exists.

from opensandbox.models.sandboxes import Host, Volume

volumes = [
    Volume(
        name="win-storage",
        host=Host(path="/data/opensandbox/windows-storage"),
        mount_path="/storage",
        read_only=False,
    ),
]
# Pass as SandboxSync.create(..., volumes=volumes, ...)

Existing ISO on the host

Bind a local Windows install ISO read-only to /boot.iso to avoid downloading media each time (also requires allowed_host_paths; the path must be a file):

from opensandbox.models.sandboxes import Host, Volume

volumes = [
    Volume(
        name="win-iso",
        host=Host(path="/data/iso/Win11_23H2.iso"),
        mount_path="/boot.iso",
        read_only=True,
    ),
]

Customizing dockur/windows

dockur/windows is configured with environment variables. OpenSandbox passes your env into the container as documented upstream. Install / UX settings often include:

• VERSION: Windows variant code (e.g. 11, 11l, 10 — full table in the project README) or, in some cases, a custom ISO https:// URL
• USERNAME / PASSWORD: first user and password (defaults in the image if omitted — see upstream)
• LANGUAGE: install language (e.g. English, Chinese)
• REGION / KEYBOARD: locale and layout (e.g. en-US, zh-CN)
• Advanced cases may use DHCP, ARGUMENTS (extra QEMU args), etc. — see the dockur/windows FAQ

If you already set CPU, memory, and disk via resourceLimits, do not repeat the same resource keys in env as in the dockur docs; see resourceLimits vs. environment variables above. Other non-resource keys can be combined freely.

env = {
    "VERSION": "11l",
    "USERNAME": "Docker",
    "PASSWORD": "your-secure-password",
    "LANGUAGE": "Chinese",
    "REGION": "zh-CN",
    "KEYBOARD": "zh-CN",
}

For the full list, defaults, and interactions, use the dockur/windows repository and image tags.

Using your own Windows image

In dockur/windows documentation, “your own” usually means which Windows install ISO to use — not a custom recipe unrelated to upstream. The custom install FAQ states:

• For an ISO not in the project’s version table, set VERSION to the ISO’s download URL (https://...); the container fetches and installs it.
• If you already have a local ISO file, bind it to /boot.iso as in Existing ISO on the host above; upstream documents that VERSION is then ignored.

In OpenSandbox, set VERSION in env and, when needed, add a volume for the local ISO at /boot.iso, matching the upstream flow; keep image as dockurr/windows or another compatible upstream image, as in the other examples.

Snippet for the VERSION = ISO URL case (same as passing env in the minimal example):

env = {
    "VERSION": "https://example.com/path/to/your.iso",
    # same pattern as the minimal example for resource / platform / etc.
}

FAQ

• Unsupported platform.os 'windows' on create — server build has no Windows profile; upgrade to a version that includes it.

• INVALID_PARAMETER for resourceLimits.* — ensure cpu >= 2, memory >= 4G, disk >= 64G.

• Stays Pending a long time — first Windows install is slow; check host resources and /storage space, and increase wait timeouts.

• Status Running but endpoint unreachable — verify GET /v1/sandboxes/{id}/endpoints/44772 returns a valid address; set env.USER_PORTS if you need more ports forwarded.