paularah / cri-dockerd

dockerd as a compliant Container Runtime Interface for Kubernetes

cri-dockerd

This adapter provides a shim for Docker Engine that lets you control Docker via the Kubernetes Container Runtime Interface.

IMPORTANT

For users running 0.2.5 or above, the default network plugin is cni. Kubernetes 1.24+ has removed kubenet and other network plumbing from upstream as part of the dockershim removal/deprecation. In order for a cluster to become operational, Calico, Flannel, Weave, or another CNI should be used.

For CI workflows, basic functionality can be provided via containernetworking/plugins.

Motivation

Mirantis and Docker have agreed to partner to maintain the shim code standalone outside Kubernetes, as a conformant CRI interface for the Docker Engine API. For Mirantis customers, that means that Docker Engine’s commercially supported version, Mirantis Container Runtime (MCR), will be CRI compliant. This means that you can continue to build Kubernetes based on the Docker Engine as before, just switching from the built in dockershim to the external one.

Mirantis and Docker intend to work together on making sure it continues to work as well as before and that it passes all the conformance tests and continues to work just like the built in version did. Mirantis will be using this in Mirantis Kubernetes Engine, and Docker will continue to ship this shim in Docker Desktop.

You can find more information about the context for this tool in Don't Panic: Kubernetes and Docker and on the Mirantis blog.

Build and install

To begin following the build process for this code, clone this repository in your local environment:

To use with Kubernetes

The default network plugin for cri-dockerd is set to cni on Linux. To change this, --network-plugin=${plugin} can be passed in as a command line argument if invoked manually, or the systemd unit file (/usr/lib/systemd/system/cri-docker.service if not enabled yet, or /etc/systemd/system/multi-user.target.wants/cri-docker.service as a symlink if it is enabled) should be edited to add this argument, followed by systemctl daemon-reload and restarting the service (if running)

git clone https://github.com/Mirantis/cri-dockerd.git

The above step creates a local directory called cri-dockerd which you will need for the following steps.

To build this code (in a POSIX environment):

cd cri-dockerd
mkdir bin
VERSION=$((git describe --abbrev=0 --tags | sed -e 's/v//') || echo $(cat VERSION)-$(git log -1 --pretty='%h')) PRERELEASE=$(grep -q dev <<< "${VERSION}" && echo "pre" || echo "") REVISION=$(git log -1 --pretty='%h')
go build -ldflags="-X github.com/Mirantis/cri-dockerd/version.Version='$VERSION}' -X github.com/Mirantis/cri-dockerd/version.PreRelease='$PRERELEASE' -X github.com/Mirantis/cri-dockerd/version.BuildTime='$BUILD_DATE' -X github.com/Mirantis/cri-dockerd/version.GitCommit='$REVISION'" -o cri-dockerd

To build for a specific architecture, add ARCH= as an argument, where ARCH is a known build target for golang

To install, on a Linux system that uses systemd, and already has Docker Engine installed

# Run these commands as root
###Install GO###
wget https://storage.googleapis.com/golang/getgo/installer_linux
chmod +x ./installer_linux
./installer_linux
source ~/.bash_profile

cd cri-dockerd
mkdir bin
go build -o bin/cri-dockerd
mkdir -p /usr/local/bin
install -o root -g root -m 0755 bin/cri-dockerd /usr/local/bin/cri-dockerd
cp -a packaging/systemd/* /etc/systemd/system
sed -i -e 's,/usr/bin/cri-dockerd,/usr/local/bin/cri-dockerd,' /etc/systemd/system/cri-docker.service
systemctl daemon-reload
systemctl enable cri-docker.service
systemctl enable --now cri-docker.socket