The document discusses Docker's support for multiple CPU architectures and operating systems through multi-architecture container images and orchestration. It explains how Docker images are tied to a specific OS and CPU, requiring multi-arch images to run universally. It demonstrates building and distributing multi-arch images, and how Docker Swarm and Compose support placement and constraints for multi-arch orchestration. It concludes that maintaining multi-arch images takes effort but provides portability, and that Docker EE supports orchestrating Linux, Windows, IBM Z and Power systems through one interface.

1. Docker:
Multi-arch All
The Things
Phil Estes
IBM Cloud @estesp
Michael Friis
Docker, Inc. @friism

2. Agenda
● Docker Engine across Multiple
CPU and OS Platforms
● Container Images for Multiple
Platforms and Architectures
● Multi-Architecture Orchestration
linux/amd64
linux/arm64
linux/arm
linux/s390x
linux/ppc64le
windows/amd64

3. Multi-arch in action!
$ docker run golang go version
Go version go1.9.1 <os/arch>
$
* https://blog.docker.com/2017/09/docker-official-images-now-multi-platform/

4. Docker Platform Expansion
2014 2015 2016 2017
2013-14 Docker on x86_64
April 2015: Docker client
on Windows
June 2015: Docker
engine on Raspberry
Pi (ARMv5), z13 (s390x
mainframe), and
Power Systems
June 2016: Docker engine
in Windows 10 Preview
April 2017: Docker EE
official support for IBM
z/LinuxONE and Power
Systems
Go runtime porting to s390x,
ppc64le, improvements to
ARM/other embedded CPUs
2014-2015

5. Why do we care?
> Docker runs across many operating
environments/CPU architectures
> Portability and ease of use are core
Docker tenets
Goal: Building and running applications on
Docker should works the same anywhere!

6. Container Images for
Different Platforms

7. Containers != VMs
Containers:
● Do not virtualize hardware or kernel
○ Great for performance and density
○ But, stuck with host CPU/kernel
● Can’t “emulate” CPU arch capability**
○ Can’t run Windows containers on Linux host
○ or z/Linux containers on x86_64 Linux host
** caveat: qemu “binfmt” support on Linux
We must build multi-arch images
Docker Hub
nginx microsoft/iis

8. Manifest lists
Required: image type support
for per-platform images
● The Docker v2.2 image spec
met this requirement (Jan 2016)
● Included a new media type: “v2
manifest list”
A manifest list contains
platform segregated
references to single-platform
manifest entries
$ docker run mplatform/mquery golang
Image: golang
* Manifest List: Yes
* Supported platforms:
- amd64/linux
- arm/linux (variant: v7)
- arm64/linux (variant: v8)
- 386/linux
- ppc64le/linux
- s390x/linux

9. Image
Manifests
{
"schemaVersion": 2,
"mediaType": "application/vnd.docker.distribution.manifest.list.v2+json",
"manifests": [
{
"mediaType": "application/vnd.docker.distribution.manifest.v1+json",
"size": 2094,
"digest": "sha256:7820f9a86d4ad15a2c4f0c0e5479298df2aa7c2f6871288e2ef8546f3e7b6783",
"platform": {
"architecture": "ppc64le",
"os": "linux"
}
},
{
"mediaType": "application/vnd.docker.distribution.manifest.v1+json",
"size": 1922,
"digest": "sha256:ae1b0e06e8ade3a11267564a26e750585ba2259c0ecab59ab165ad1af41d1bdd",
"platform": {
"architecture": "amd64",
"os": "linux",
"features": [
"sse"
]
}
},
{
"mediaType": "application/vnd.docker.distribution.manifest.v1+json",
"size": 2084,
"digest": "sha256:e4c0df75810b953d6717b8f8f28298d73870e8aa2a0d5e77b8391f16fdfbbbe2",
"platform": {
"architecture": "s390x",
"os": "linux"
}
},
{
"mediaType": "application/vnd.docker.distribution.manifest.v1+json",
"size": 2084,
"digest": "sha256:07ebe243465ef4a667b78154ae6c3ea46fdb1582936aac3ac899ea311a701b40",
"platform": {
"architecture": "arm",
"os": "linux",
"variant": "armv7"
}
},
{
"mediaType": "application/vnd.docker.distribution.manifest.v1+json",
"size": 2090,
"digest": "sha256:fb2fc0707b86dafa9959fe3d29e66af8787aee4d9a23581714be65db4265ad8a",
"platform": {
"architecture": "arm64",
"os": "linux",
"variant": "armv8"
}
Index (Manifest List)
linux amd64
linux ppc64le
windows amd64
Manifests:
Manifest
linux arm64
Layers:
Config:
L0
L1
Ln
Root Filesystem
/usr
/bin
/dev
/etc
/home
/lib
C
OCI Runtime Spec
process
args
env
cwd
…
root
mounts

10. Status of multi-arch images
Official Docker images
Microsoft .NET Core
LinuxKit
Lots of ARM projects

11. DEMO: Build multi-arch images

12. Dockerfile maintenance
Same OS = probably same (or very
similar) Dockerfile
Different OS = probably different
Dockerfiles

13. FROM microsoft/nanoserver:10.0.14393.1770
RUN Invoke-WebRequest $Env:DOWNLOAD_URL -OutFile dotnet.zip;
Expand-Archive dotnet.zip -DestinationPath
$Env:ProgramFilesdotnet;
Remove-Item -Force dotnet.zip
RUN setx /M PATH $($Env:PATH + ';' + $Env:ProgramFiles + 'dotnet')
FROM microsoft/dotnet:2.0-runtime-deps-jessie
RUN apt-get update
&& apt-get install -y --no-install-recommends
curl
&& rm -rf /var/lib/apt/lists/*
RUN curl -SL $DOWNLOAD_URL --output dotnet.tar.gz
&& echo "$DOWNLOAD_SHA dotnet.tar.gz" | sha512sum -c -
&& mkdir -p /usr/share/dotnet
&& tar -zxf dotnet.tar.gz -C /usr/share/dotnet
&& rm dotnet.tar.gz
&& ln -s /usr/share/dotnet/dotnet /usr/bin/dotnet

14. Multiplatform CI Setup
git push
Container
Registry
Run Unit Tests
Build App
docker image build
Credit: Stefan Scherer
docker image push
docker manifest push
docker image push

15. Multi-architecture
Orchestration

16. Multiplatform Orchestration
> Requires arch-aware
orchestrator
● Images can continue to be CPU and/or OS
specific (for example: Windows or Linux-only
software; software not ported to multi-CPU)
● Even if images are multi-platform you may
choose to run particular workloads on
certain hardware/OS platforms
Image registry
Windows
Linux
x86_64
Linux
s390x

17. Multi-arch: Swarm support
> Placement Engine
● Reads manifest list’s platform
entries
● Matches engine nodes with
platforms supported
> Docker Compose
● Can specify manual
constraints in YAML
"Placement": {
"Constraints": [
"node.platform.arch == s390x"
],
"Platforms": [
{
"Architecture": "amd64",
"OS": "linux"
},
{
"Architecture": "arm",
"OS": "linux"
},
{
"Architecture": "arm64",
"OS": "linux"
},
{
"Architecture": "ppc64le",
"OS": "linux"
},
docker service inspect

18. DEMO: Orchestration
Docker
Enterprise
Edition

19. Conclusion

20. Take-aways
Container images are specific to the OS and
CPU they’re built on
Maintain Docker images? Making them
multi-arch takes effort (but it’s worth it)
Docker EE supports Linux, Windows, IBM Z and
Power with one pane of glass

21. Thanks!
Phil Estes
IBM Cloud @estesp
Michael Friis
Docker, Inc. @friism

22. Docker EE
Hosted Demo
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