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osrun

A docker container to run Windows commands and processes. Windows is downloaded, installed, snapshotted and made available for fast access.

Features

  • ⚡️ Super fast execution once image is cached (2-3 seconds to start from snapshot)
  • 🖥️ Browser-based VNC server to view the Windows desktop (forward port 8000)
  • ⌨️ Support for interactive commands (like cmd.exe or powershell.exe) and piping stdin/stdout
  • 🖱️ GUI apps (like notepad.exe or chrome.exe) are supported
  • 🌍 Windows 11 is automatically downloaded and installed from Microsoft's servers
  • 📸 Snapshot support to quickly load different states
  • 🐳 All available as a convenient Docker image!

Usage

# Linux
docker run -it --rm --device=/dev/kvm -v $(pwd)/cache:/cache ghcr.io/lg/osrun 'dir "C:\Program Files"'

# MacOS (installation will be very slow)
docker run -it --rm -v $(pwd)/cache:/cache ghcr.io/lg/osrun 'dir "C:\Program Files"'
 Volume in drive C is Windows 11
 Volume Serial Number is F48D-7158

 Directory of C:\Program Files

08/06/2023  09:24 PM    <DIR>          .
05/06/2022  10:42 PM    <DIR>          Common Files
05/07/2022  12:38 AM    <DIR>          Internet Explorer
...

Usage: osrun [flags] '<command>'
Short-lived containerized Windows instances

  -h --help: Display this help
  -v --verbose: Verbose mode

Install
  -k --keep: Keep install artifacts after successful provisioning

Run
  -f --forward-port <port>: Passes through a port to the VM (ex: 3389)
  -d --drive <path>: Use the specified drive image (default: /cache/win11.qcow2)
  -p --pause: Do not close the VM after the command finishes
  -n --new-snapshot <name>: Generate a new snapshot after the command finishes
  -s --use-snapshot <name>: Restore from the specified snapshot (default: provisioned)

Developing

# Build the container
docker build -t osrun .

# Install Windows and run a command
docker run -it --rm --device=/dev/kvm -v $(pwd)/cache:/cache -p 8000:8000 osrun -k -v -p 'dir "C:\Program Files"'

This project is intended to be developed inside of VSCode. Because the KVM acceleration is substantial, it's suggested that you either run things on a Linux machine or use VSCode's Remote functionality to remotely develop on a Linux machine (and port forward port 8000 for noVNC).

Protips

  • Don't forget to mount the cache directory in Docker and passthrough kvm
  • Use single quotes around the run command to avoid shell expansion. There is no need for double backslashes in Windows paths. Ex: osrun 'dir "C:\Program Files"'.
  • Take advantage of noVNC, --verbose and --pause to debug installation/execution.
  • Enable auto-reconnect on noVNC and also use "Local Scaling" and "Show Dot when No Cursor".
  • You can inspect the container state using docker exec -it <container-id> ash.
  • You can enter the QEMU Monitor using docker exec -it <container-id> socat tcp:127.0.0.1:55556 readline or just socat tcp:127.0.0.1:55556 readline locally if you forwarded the port.
  • When using --forward-port for a 127.0.0.1-bound port on the VM, you can add a proxy in Windows like the following: echo netsh interface portproxy add v4tov4 listenaddress=10.0.2.15 listenport=YOUR_PORT connectaddress=127.0.0.1 connectport=YOUR_PORT > c:\\port.bat & start /min c:\\port.bat & YOUR_ORIGINAL_COMMAND

Details

This container uses QEMU to run a Windows 11 VM. Windows 11 is built with the file list from UUP dump (or a backup server) and files are downloaded directly from Microsoft's Windows Update servers. The UUP dump script generates a Windows ISO into which we then add an autounattend.xml script to start the installation automation. To keep the resultant VM small (~6GB) and fast we remove a lot of the default Windows components and services including Windows Defender, Windows Update, Edge, most default apps, and also disable things like paging, sleep and hibernation, plus the hard drive is compressed and trimmed. This process is done by the files in the win11-init directory. This image and VM state is then snapshotted when the system is stable and is saved to a cache directory so that subsequent runs start quickly. When running, SIGINT and SIGTERM are supported to gracefully shutdown the VM by passing the signal through.

On a reasonably modern machine the installation process takes about 20 minutes end-to-end and runs take about 2-3 seconds for simple commands like dir. Without KVM expect the installation to take about 2-3 hours and runs to take about 30 seconds even on fast machines like the M2 Macs.

flowchart LR
  subgraph Z["Installer preparation"]
    A["Windows Setup file-list assembled"]
    -->
    A1["UUPDump script generates Setup ISO"]
    -->
    A2["autounattend.xml injected into ISO"]
    --"win11-clean.iso artifact prepared"-->
    A3["QEMU mounts ISO and starts VM"]
  end

  subgraph ZA["Installation process"]
    B-1["noVNC started on port 8000 for debugging"]
    -->
    B["Setup runs autounattend.xml"]
    --Artifact saved: /cache/win11-step0-HASH.qcow2-->
    B1["boot-0.ps1 as NT AUTHORITY/SYSTEM"]
    --Artifact saved: /cache/win11-step1-HASH.qcow2-->
    B2["boot-1.ps1 as Administrator"]
    --Artifact saved: /cache/win11-step2-HASH.qcow2-->
    B2.1["Artifacts joined and compressed into /cache/win11.qcow2 (or --drive path)"]
    -->
    B3["Ncat Agent waits for boot"]
    --'provisioned' snapshot saved to drive image\nAll other artifacts removed-->
    B4["Ready to run"]
  end

  subgraph ZB["Running"]
    C0["noVNC started on port 8000 for debugging"]
    -->
    C1["QEMU snapshot restored"]
    --/tmp/qemu-status mounted as \\10.0.2.4\qemu in Windows-->
    C2["Clock set to proper time"]
    -->
    C3["Command executed using Ncat through C:\agent.bat"]
    --stdin/stdout piped-->
    C4["New snapshot optionally created via QEMU Monitor"]
    -->
    C5["Exit code returned"]
  end

  Z-->ZA
  ZA-->ZB
Loading

Communication between the QEMU VM and the Docker container is done via Netcat (ncat in particular). A variety of other options were explored like ssh, QEMU Agent, WinRM and WMIC, but most options don't make Desktop-interactivity possible (so you can't launch things like web browsers or Notepad, etc). During installation and execution, multiple debugging services are started (you'll need to forward these ports using Docker if you want to use them outside the container):

  • a noVNC HTTP server is started on port 8000 to view the VM's display,
  • the raw QEMU-run VNC server is also available on port 5950 (not compatible with Apple Screen Sharing) if you don't prefer noVNC,
  • the QEMU Monitor (ie. command-line interface) is available on port 55556 (supported commands are here),
  • the QEMU Guest Agent is available on port 44444 (its JSON protocol is here) and
  • the Ncat agent is available on port 5454 to send raw commandline commands.
flowchart LR
  subgraph "Host machine"
    subgraph "Docker Container"
      subgraph "QEMU VM"
        A[["\\10.0.2.4\qemu"]]
        S[["C:\agent.bat"]]
        D["virtio display"]
        I["QEMU Agent"]
        A<--When installing---O[["\\10.0.2.4\qemu\status.txt"]]
      end

      A<-->B[["/tmp/qemu-status"]]
      D-->E["QEMU VNC server"]
      G["QEMU Monitor"]
      K[["/cache"]]
      L[["/win11-init/*.ps1"]]-.Mounted into on install.->A
      E-.Port 5950.->R["HTTP server w/ websockets proxy"]
    end

    P-.Port 5454.->Q["Ncat agent"]
    R-.Port 8000.->Q["noVNC HTTP frontend"]
    E-.Port 5950.->F["VNC client"]
    G-.Port 55556.->H["QEMU Monitor client"]
    I-.Port 44444.->J["QEMU Agent client"]
    K--Docker Volume-->M[["Directory"]]
  end
Loading

The --drive flag

Due to limitations in QEMU, even though we load a snapshot every time the image will still get written to and will therefore grow over time. Additionally in a shared-mount scenario, only one VM will be able to access this drive at the same time due to QEMU's locking. One workaround is to copy your drive image to another temporary directory (perhaps even a tmpfs mount) and then use this --drive flag to reference it.

The --new-snapshot and --use-snapshot flags

While the final image will always have a provisioned snapshot, you can create new snapshots from the VM end-state of your command using the --new-snapshot <name> flag. You can then use this snapshot for subsequent runs using the --use-snapshot <name> flag. This is useful if you need to change the VM's configuration or install a tool on top of the base provisioned snapshot. Behind the scenes this uses the savevm and loadvm commands on the QEMU Monitor protocol which snapshots memory and disk state into the main qcow2 image.

As an example (in order):

  1. osrun --new-snapshot greeted 'mkdir C:\hello'

    flowchart LR
  A["'provisioned' snapshot restored"]
  -->B["mkdir executed"]
  -->C["New 'greeted' snapshot created"]
    Loading

  2. osrun --use-snapshot greeted 'dir C:\'

    flowchart LR
  A["'greeted' snapshot restored"]
  -->B["dir executed, will display the 'hello' directory"]
    Loading

  3. osrun 'dir C:\'

    flowchart LR
  A["'provisioned' snapshot restored"]
  -->B["dir executed, will not display the 'hello' directory"]
    Loading

TODO

  • Add support for Windows 10 / MacOS
  • Figure out if hvf acceleration is at all possible for MacOS
  • Add exit code and stderr support again