LinuxKit based LCOW images

This repository hosts the components to build a LinuxKit based Linux image for Linux Containers on Windows.

Note: LCOW support was experimental and is no longer being developed. This repository is now archived.

Use

This section describes how to use Linux Containers on Windows with LinuxKit.

Prerequisites

To use Linux Containers on Windows you need a Windows build supporting the feature, i.e., Windows 10 Pro or Windows Server 2016 1709 (or newer Insider builds). You also need to have Hyper-V and the Container feature enabled.

Setup

For now, you need a recent version of docker, such as a nightly build from the master branch. In PowerShell:

Invoke-WebRequest -UseBasicParsing -OutFile docker.zip https://master.dockerproject.com/windows/x86_64/docker.zip
Expand-Archive docker.zip -DestinationPath $Env:ProgramFiles

Next, you need to get the LinuxKit images. You can either build them yourself (see below) or download the latest zip file from the releases page. Then unzip in an elevated PowerShell:

Remove-Item "$env:ProgramFiles\Linux Containers" -Force -Recurse
Expand-Archive release.zip -DestinationPath "$Env:ProgramFiles\Linux Containers\."
rm release.zip

Run

On recent docker master builds (master-dockerproject-2018-01-20, build 44a1168a or newer):

Start the docker daemon (in an elevated PowerShell):

.\dockerd.exe -D --experimental

You should now be able to run Linux containers on Windows, e.g.:

docker run --platform linux --rm -ti busybox sh

On older docker master builds:

Start the docker daemon (in an elevated PowerShell):

$env:LCOW_SUPPORTED=1
$env:LCOW_API_PLATFORM_IF_OMITTED="linux"
Remove-Item c:\lcow -Force -Recurse; mkdir c:\lcow
.\dockerd.exe -D --experimental --data-root c:\lcow

(Note: If your kernel is older than 4.14 and is configured with KASLR you may want to add --storage-opt lcow.bootparameters="nokaslr" to the dockerd command line.)

You should now be able to run Linux containers on Windows, e.g.:

docker run --rm -ti busybox sh

If you already have docker installed on your system you probably want to start the daemon (and the client) on a non-standard named pipe using the -H "npipe:////./pipe//docker_lcow" for both.

Build

The LinuxKit image is build from lcow.yml and the main package is called init-lcow.

Prerequisites

To build images and packages you will need the LinuxKit tool. You also need to have a working Docker installation.

If you already have go installed you can use go get -u github.com/linuxkit/linuxkit/src/cmd/linuxkit to install the linuxkit tool.

On macOS there is a brew tap available. Detailed instructions are at linuxkit/homebrew-linuxkit, but the short summary is:

brew tap linuxkit/linuxkit
brew install --HEAD linuxkit

Building the LCOW image

Simply type:

make

which generates kernel and initrd.img which need to be copied to "$env:ProgramFiles\Linux Containers\kernel" on your Windows system.

Alternatively, use:

linuxkit build lcow.yml

This will generate three files: lcow-kernel, lcow-initrd.img, and lcow-cmdline. lcow-kernel needs to be copied to "$env:ProgramFiles\Linux Containers\kernel" and lcow-initrd.img to "$env:ProgramFiles\Linux Containers\initrd.img".

Building the init-lcow package

The init-lcow contains a minimal init system used inside the LCOW and mainly consists of the OpenGCS deamon. To rebuild the package use the linuxkit tool:

linuxkit pkg build -org foo pkg/init-lcow

This should create a local image foo/init-lcow:<tag> which can be used lcow.yml. To build and push the image to hub use:

linuxkit pkg build -org <your hub name> -disable-content-trust pkg/init-lcow

You can omit -disable-content-trust if your registry has Docker Content Trust enabled.

Test

The tests directory contains a number of tests for LCOW written using rtf. To run them you can simply execute RunTests.ps1 inside the .\tests directory. It will pick up the kernel/initrd in the parent directory if present. Alternatively, it can download the artefact from CircleCI if you supply the build number. The script will also download the latest version of docker and the version of the rtf binary.

Test results will be stored in .\tests\_results\<UUID> directory where <UUID> is the UUID printed out during the test run.

To manually run the test, make sure you have a working LCOW system set up. You'll also need a copy of the rtf.exe binary (see RunTests.ps1 on how to obtain it or go get .. it). Further, docker must also be in your path.

To run tests, use rtf run inside the .\tests directory. To list which tests are available use rtf list or rtf info. To run an individual test or a group of tests use rtf run <name>.