ekstrap

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