ekstrap

ekstrap is a simple tool to bootstrap the configuration on Kuberntes nodes so that they may join an EKS cluster.

Usage

When run on an ec2 node ekstrap performs several tasks.

Discovers the name of your EKS cluster by looking for the kubernetes.io/cluster/<name> tag.
Discovers the endpoint and CA certificate of your EKS cluster.
Updates the hostname of the node to match the PrivateDnsName from the EC2 API.
Writes a kubeconfig file configured to connect to your EKS cluster to /var/lib/kubelet/kubeconfig.
Writes a systemd unit file to /lib/systemd/system/kubelet.service.
Writes the cluster CA certificate to /etc/kubernetes/pki/ca.crt.
Calculates an appropriate value for for --kube-reserved
Restarts the kubelet unit.

In order to run ekstrap your instance should have an IAM instance profile that allows the EC2::DescribeInstances action and the EKS::DescribeCluster action. Both of these actions are already included in the AWS managed policy arn:aws:iam::aws:policy/AmazonEKSWorkerNodePolicy along with the other permissions that the kubelet requires to connect to your cluster, it is recommended therefore to simply attach this policy to your instance role/profile.

Extra Arguments

If you wish to provide extra aruguments to the kubelet you can create a drop-in that sets the KUBELET_EXTRA_ARGS environment variable.

For example to taint nodes with GPU hardware you could add:

/etc/systemd/system/kubelet.service.d/40-kubelet-extra-args.conf

[Service]
Environment='KUBELET_EXTRA_ARGS=--register-with-taints="gpu=true:PreferNoSchedule"'

Installation

The simplest way to install ekstrap is to use our packagecloud repository.

If installed with the package a systemd unit will be installed and enabled, (but not started) so ekstrap will be run on the next boot.

Debian / Ubuntu

Follow the instructions here to add our repository.

Or run:

curl -s https://packagecloud.io/install/repositories/errm/ekstrap/script.deb.sh | sudo bash

Then install ekstrap:

sudo apt-get install ekstrap

Fedora / RHEL / Amazon Linux

Follow the instructions here to add our repository.

For Amazon Linux use the string for Enterprise Linux 6 (el/6)

Or run:

curl -s https://packagecloud.io/install/repositories/errm/ekstrap/script.rpm.sh | sudo bash

Then install ekstrap:

sudo yum install ekstrap

Manual Instalation

ekstrap is also distributed as a static binary so can be installed on any appropriate system with simple tools.

$ curl -LO https://github.com/errm/ekstrap/releases/download/v0.0.4/ekstrap_0.0.4_linux_x86_64

You should check that the provided checksums match before you use the binary.

$ curl -LO https://github.com/errm/ekstrap/releases/download/v0.0.4/ekstrap_checksums.txt
$ sha256sum -c ekstrap_checksums.txt
ekstrap_0.0.4_linux_x86_64: OK

Install the ekstrap binary into a suitable location e.g. /usr/sbin/ekstrap

$ install -m755 ekstrap_0.0.4_linux_x86_64 /usr/sbin/ekstrap

You might choose to run ekstrap with a oneshot unit

[Unit]
Description=Configures Kubernetes EKS Worker Node
Before=kubelet.service

[Service]
Type=oneshot
ExecStart=/usr/sbin/ekstrap
RemainAfterExit=true

[Install]
WantedBy=multi-user.target

Remember that because ekstrap writes config files with strict permissions and interacts with the init system, it needs to run as root.

Build from source

Install go
Checkout the git repo / grab the latest source tarball
Copy the source to $GOPATH/src/github.com/errm/ekstrap
Run make install

Development

make

Will run the tests and build a binary

Linting

We run some linting processes on GolangCI

To run locally: make lint

Dependencies

To build ekstrap you need go

If you want a tiny binary, install upx and run the make compress task.

ekstrap currently only works with systemd, if you want us to support another init system please comment here https://github.com/errm/ekstrap/issues/28.

Contributing

If you want to contribute to this tool:

Thank You!
Open an issue
Or a PR
Try to write tests if you are adding code / features

Thanks

License

Apache 2.0

errm / ekstrap

readme