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Improving Docker with Unikernels: Introducing
HyperKit, VPNKit and DataKit
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8/17/2019 Improving Docker With Unikernels_ Introducing HyperKit, VPNKit and DataKit _ Docker Blog
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By Anil Madhavapeddy (https://blog.docker.com/author/anil/) May 18, 2016
Share
this:
(http://www.linkedin.com/shareArticle?mini=true&url=https://blog.doc
source/&title=Improving%20Docker%20with%20Unikernels%3A%20Introducing%20Hypbeen working hard to build native Docker for Mac and Windows apps to ensure that yourmost popular developer operating systems. Docker for Mac and Windows include everytefficiently bridges storage and ...) (http://www.reddit.com/submit?url=https://blo
source/&title=Improving%20Docker%20with%20Unikernels%3A%20Introducing%20Hyp
(https://plus.google.com/share?url=https://blog.docker.com/2016/05/docker-unikernels-o(http://news.ycombinator.com/submitlink?u=https://blog.docker.com/2016/05/docker-uniksource/&t=Improving%20Docker%20with%20Unikernels%3A%20Introducing%20Hyper
docker for mac (https://blog.docker.com/tag/docker-for-mac/), docker for windows(https://blog.docker.com/tag/docker-for-windows/), open source
(https://blog.docker.com/tag/open-source/), OSCON (https://blog.docker.com/tag/oscon/)
13 14
1
We’ve been working hard to build native Docker for Mac and Windows apps
(https://blog.docker.com/2016/03/docker-for-mac-windows-beta/) to ensure that your
Docker experience is as seamless as possible on the most popular developer operating
systems. Docker for Mac and Windows include everything required to spin up a Linux
Docker container that efficiently bridges storage and networking from the host into the
Docker containers. They work transparently on both MacOS X and Windows, andrequire no other third party software.
Docker has always been built on open-source foundations: Solomon Hykes is presenting a
keynote today at OSCON 2016 about the incremental revolution
(http://conferences.oreilly.com/oscon/open-source-us/public/schedule/detail/51393) that
the firehose of collaborative open source development has enabled throughout Docker’s
history. Today, we are adding to our existing open source contributions by open sourcing
the core technology that powers the Docker for Mac and Windows desktop applications!
Building Docker for Mac and Windows has required integrating hardware virtualization,
embedded operating systems and unikernel technology, all without exposing this magic to
the end user. Let’s take a look under the hood of our applications to understand what
some of this source code does, and give you a better of idea of how to contribute to it or
use it in your own projects.
8/17/2019 Improving Docker With Unikernels_ Introducing HyperKit, VPNKit and DataKit _ Docker Blog
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When you run Docker for Mac, it spins up a lightweight hypervisor that exists solely to run
a single, embedded Linux instance that includes the latest stable release of Docker
Engine. Unlike most hypervisors, this requires no special admin privileges since it uses the
included Hypervisor Framework
(https://developer.apple.com/library/mac/documentation/DriversKernelHardware/Reference
since OSX 10.10). The Docker application also bundles libraries that supply the Docker
VM with host networking and storage capabilities that map intelligently between Linux and
OSX/Windows semantics.
(https://github.com/docker/)
Today, we are excited to announce the open-sourcing of these discrete components, the same
source code we use in the release builds of Docker for Mac and Windows. The new
components are:
HyperKit (https://github.com/docker/hyperkit): A lightweight virtualization toolkit on
OSX
DataKit (https://github.com/docker/datakit): A modern pipeline framework for
distributed components
VPNKit (https://github.com/docker/vpnkit): A library toolkit for embedding virtual
8/17/2019 Improving Docker With Unikernels_ Introducing HyperKit, VPNKit and DataKit _ Docker Blog
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networking
Each of these kits can be used independently or together to form a complete product such
as Docker for Mac or Windows. This is just the beginning: we will open
more components in the future as they mature (e.g. the filesystem framework). They all
have a set of curated Pioneer Projects for beginners to take on: HyperKit
(https://github.com/docker/hyperkit/issues?
q=is%3Aissue+is%3Aopen+label%3A%22help+wanted%22), DataKit
(https://github.com/docker/datakit/issues?
q=is%3Aissue+is%3Aopen+label%3A%22help+wanted%22), and VPNKit
(https://github.com/docker/vpnkit/issues?
q=is%3Aissue+is%3Aopen+label%3A%22help+wanted%22).
(https://github.com/docker/)
HyperKit
HyperKit is based around a lightweight approach to virtualization that is possible due to
the Hypervisor framework
(https://developer.apple.com/library/mac/documentation/DriversKernelHardware/Reference
8/17/2019 Improving Docker With Unikernels_ Introducing HyperKit, VPNKit and DataKit _ Docker Blog
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with MacOS X 10.10 onwards. HyperKit applications can take advantage of hardware
virtualization to run VMs, but without requiring elevated privileges or complex management
tool stacks.
HyperKit is built on the xHyve (https://github.com/mist64/xhyve) and bHyve
(http://bhyve.org/) projects, with additional functionality to make it easier to interface with
other components such as the VPNKit or DataKit. Since HyperKit is broadly structured as
a library, linking it against unikernel libraries is straightforward. For example, we added
persistent block device support that uses the MirageOS QCow
(https://github.com/docker/hyperkit/blob/master/src/mirage_block_ocaml.ml) libraries
written in OCaml.
How can you contribute?
There are three great areas for contribution:
Support for booting more guest operating systems. Linux is the only “first class”
operating system supported at the moment. FreeBSD does boot, but requires
running the installer and so isn’t as seamless. Patches exist to add more BIOS
support to boot Windows, OpenBSD, or NetBSD, but require more testing.
Support for more high-level language bindings. Because the HyperKit is structured
as a library, it can be interfaced with high-level languages using their normal foreign
function interfaces.
Hypervisor features. Several traditional hypervisor features such as
suspend/resume, live relocation and support for hardware performance counters are
not supported. These need to be added in the same library style as the rest of the
codebase, in order to ensure that HyperKit remains lightweight and easy to embed.
We will ensure that any contributions are structured such that they can be submitted to
their respective upstream projects.
How else can you use it?
Any applications that need to spin up specialised or short-lived virtual machines can
benefit from linking against HyperKit. These could be conventional operating systems such
as Linux, or some of the unikernel projects (http://unikernel.org/projects/) once they have
8/17/2019 Improving Docker With Unikernels_ Introducing HyperKit, VPNKit and DataKit _ Docker Blog
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been ported to HyperKit.
DataKit
DataKit is a toolkit to coordinate processes with a git-compatible filesystem interface. It
revisits the UNIX pipeline concept and the Plan9 9P protocol, but with a modern twist:
streams of tree-structured data instead of raw text. DataKit lets you define complex
workflows between loosely coupled processes using something as simple as shell scripts
interacting with a version controlled file-system.
DataKit is a rethinking of application architecture around data flows, bringing back the
wisdom of Plan 9’s “everything is a file”, in the git era where “everything is a versioned
file”. Since we are making use of DataKit and 9P heavily in Docker for Mac and Windows,
we are also open sourcing go-p9p (https://github.com/docker/go-p9p), a modern,
performant 9P library for Go.
How else can you use it?
There is a sample project using DataKit to create a Continuous Integration system in 50
lines of shell scripts in this repository: github.com/docker/datakit/tree/master/ci
(https://github.com/docker/datakit/tree/master/ci)
The README also covers DataKit integration with GitHub. DataKit can be used in any
situation where you need to coordinate processes around data, and shines when it is
around versioned data.
How can you contribute?
GitHub PR support in DataKit is still quite basic, this is an area that could use additional
contributions. DataKit could be used for a very broad set of use cases: share how you useit in your projects.
VPNKit
The VPNKit is a networking library that translates between raw Ethernet network traffic
and their equivalent socket calls in MacOS X or Windows. It is based on the MirageOS
(https://mirage.io) TCP/IP unikernel stack, and is a library written in OCaml. VPNKit is
8/17/2019 Improving Docker With Unikernels_ Introducing HyperKit, VPNKit and DataKit _ Docker Blog
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useful when you need fine-grained control over networking protocols in user-space, with
the additional convenience of being extensible in a high-level language.
How can you contribute?
VPNKit provides an interception point for all container traffic going through Docker for Mac
or Windows. It could be extended with support for packet capture and inspection, protocol
proxying to filter for particular traffic patterns, or even HTTP protocol visualisation for
debugging web applications.
How else can you use it?
If VPNKit had support for more endpoint types, it could also be used to test network traffic
without the overhead of actually generating and transmitting it. It could also be used to
build lightweight overlay networks between application components.
Next Steps
#Docker for Mac and Windows introduces new#opensource components: #HyperKit, #DataKitand #VPNKit (https://twitter.com/share?
text=%23Docker+for+Mac+and+Windows+introduces+new+%23opensource+components%3A+%23HyperKit%2C+%23DataKit+and+%23VPNKit&via=docker&related=docker&url=https://blog.docker.com/2016/05/docker-unikernels-open-source/)
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While the VPNKit and DataKit started life as quite specialised components in Docker for
Mac and Windows, we are excited by the possibilities enabled by open sourcing them. The
ideas here are by no means exhaustive, and we are looking forward to hearing about your
own projects. Please file issues in their respective bug trackers as you come across them,
or if you wish to discuss a particular idea.
And if you are at OSCON please come meet and collaborate with the maintainers of these
projects in our OSCON Contribute session (http://conferences.oreilly.com/oscon/open-
source-us/public/schedule/detail/51586) on Thursday 3 to 6 PM in Meeting Room 6. You
can find more details about the internals of Docker for Mac and Windows in the slides for
the talk I gave yesterday at OSCON
(http://www.slideshare.net/AnilMadhavapeddy/advanced-docker-developer-workflows-on-
macos-x-and-windows).
1 of 23
If you haven’t already, please sign up for the Docker for Mac and Windows beta
(https://beta.docker.com) and send us feedback to make it better as we head towards
general availability. Finally, we would once again like to thank all of the open source
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An integrated, easy-to-deploy environment for building,
assembling, and shipping applications.
efforts that made this release possible. The Docker for Mac and Windows
acknowledgements (https://dyhfha9j6srsj.cloudfront.net/OSS-LICENSES.txt) list the
hundreds of contributions that we use directly in our product, and we hope that you will
also be able to check out and benefit from today’s releases in your own creations.
Docker for Mac and Windows Beta
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docker for mac (https://blog.docker.com/tag/docker-for-mac/), docker for windows
(https://blog.docker.com/tag/docker-for-windows/), open source
(https://blog.docker.com/tag/open-source/), OSCON (https://blog.docker.com/tag/oscon/)
By Anil Madhavapeddy (https://blog.docker.com/author/anil/)
Anil Madhavapeddy is a member of technical staff at Docker, as well as faculty at the
Cambridge University Computer Laboratory. Anil was on the original team at Cambridge
that developed the Xen hypervisor and is currently hacking on the unikernel movement. Anil has a diverse background in industry at NetApp, XenSource, Citrix, Intel, and NASA.
He is an active member of the open source development community with the OpenBSD
operating system and more, as well as the steering committee chair of the Commercial
Uses of Functional Programming conference. Anil tweets at @avsm
(https://twitter.com/avsm).
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