Node bootstrapping

AmazonLinux2023

AL2023 introduced a new node initialization process nodeadm that uses a YAML configuration schema, dropping the use of /etc/eks/bootstrap.sh script.

Note

With Kubernetes versions 1.30 and above, Amazon Linux 2023 is the default OS.

Default settings for AL2

For self-managed nodes and EKS-managed nodes based on custom AMIs, eksctl creates a default, minimal, NodeConfig and automatically injects it into the nodegroups’s launch template userdata. i.e.

MIME-Version: 1.0
Content-Type: multipart/mixed; boundary=//

--//
Content-Type: application/node.eks.aws

apiVersion: node.eks.aws/v1alpha1
kind: NodeConfig
spec:
  cluster:
    apiServerEndpoint: https://XXXX.us-west-2.eks.amazonaws.com
    certificateAuthority: XXXX
    cidr: 10.100.0.0/16
    name: my-cluster
  kubelet:
    config:
      clusterDNS:
      - 10.100.0.10
    flags:
    - --node-labels=alpha.eksctl.io/cluster-name=my-cluster,alpha.eksctl.io/nodegroup-name=my-nodegroup
    - --register-with-taints=special=true:NoSchedule

--//--

For EKS-managed nodes based on native AMIs, the default NodeConfig is being added by EKS MNG under the hood, appended directly to the EC2’s userdata. Thus, in this scenario, eksctl does not need to include it within the launch template.

Configuring the bootstrapping process

To set advanced properties of NodeConfig, or simply override the default values, eksctl allows you to specify a custom NodeConfig via nodeGroup.overrideBootstrapCommand or managedNodeGroup.overrideBootstrapCommand e.g.

managedNodeGroups:
  - name: mng-1
    amiFamily: AmazonLinux2023
    ami: ami-0253856dd7ab7dbc8
    overrideBootstrapCommand: |
      apiVersion: node.eks.aws/v1alpha1
      kind: NodeConfig
      spec:
        instance:
          localStorage:
            strategy: RAID0

This custom config will be prepended to the userdata by eksctl, and merged by nodeadm with the default config. Read more about nodeadm's capability of merging multiple configuration objects here.