NodeClasses

Configure AWS-specific settings with EC2NodeClasses

Node Classes enable configuration of AWS specific settings. Each NodePool must reference an EC2NodeClass using spec.template.spec.nodeClassRef. Multiple NodePools may point to the same EC2NodeClass.

apiVersion: karpenter.sh/v1beta1
kind: NodePool
metadata:
  name: default
spec:
  template:
    spec:
      nodeClassRef:
        apiVersion: karpenter.k8s.aws/v1beta1
        kind: EC2NodeClass
        name: default
---
apiVersion: karpenter.k8s.aws/v1beta1
kind: EC2NodeClass
metadata:
  name: default
spec:
  # Required, resolves a default ami and userdata
  amiFamily: AL2

  # Required, discovers subnets to attach to instances
  # Each term in the array of subnetSelectorTerms is ORed together
  # Within a single term, all conditions are ANDed
  subnetSelectorTerms:
    # Select on any subnet that has the "karpenter.sh/discovery: ${CLUSTER_NAME}"
    # AND the "environment: test" tag OR any subnet with ID "subnet-09fa4a0a8f233a921"
    - tags:
        karpenter.sh/discovery: "${CLUSTER_NAME}"
        environment: test
    - id: subnet-09fa4a0a8f233a921

  # Required, discovers security groups to attach to instances
  # Each term in the array of securityGroupSelectorTerms is ORed together
  # Within a single term, all conditions are ANDed
  securityGroupSelectorTerms:
    # Select on any security group that has both the "karpenter.sh/discovery: ${CLUSTER_NAME}" tag
    # AND the "environment: test" tag OR any security group with the "my-security-group" name
    # OR any security group with ID "sg-063d7acfb4b06c82c"
    - tags:
        karpenter.sh/discovery: "${CLUSTER_NAME}"
        environment: test
    - name: my-security-group
    - id: sg-063d7acfb4b06c82c

  # Optional, IAM role to use for the node identity.
  # The "role" field is immutable after EC2NodeClass creation. This may change in the
  # future, but this restriction is currently in place today to ensure that Karpenter
  # avoids leaking managed instance profiles in your account.
  # Must specify one of "role" or "instanceProfile" for Karpenter to launch nodes
  role: "KarpenterNodeRole-${CLUSTER_NAME}"

  # Optional, IAM instance profile to use for the node identity.
  # Must specify one of "role" or "instanceProfile" for Karpenter to launch nodes
  instanceProfile: "KarpenterNodeInstanceProfile-${CLUSTER_NAME}"

  # Optional, discovers amis to override the amiFamily's default amis
  # Each term in the array of amiSelectorTerms is ORed together
  # Within a single term, all conditions are ANDed
  amiSelectorTerms:
    # Select on any AMI that has both the "karpenter.sh/discovery: ${CLUSTER_NAME}" tag
    # AND the "environment: test" tag OR any AMI with the "my-ami" name
    # OR any AMI with ID "ami-123"
    - tags:
        karpenter.sh/discovery: "${CLUSTER_NAME}"
        environment: test
    - name: my-ami
    - id: ami-123

  # Optional, use instance-store volumes for node ephemeral-storage
  instanceStorePolicy: RAID0

  # Optional, overrides autogenerated userdata with a merge semantic
  userData: |
    echo "Hello world"    

  # Optional, propagates tags to underlying EC2 resources
  tags:
    team: team-a
    app: team-a-app

  # Optional, configures IMDS for the instance
  metadataOptions:
    httpEndpoint: enabled
    httpProtocolIPv6: disabled
    httpPutResponseHopLimit: 2
    httpTokens: required

  # Optional, configures storage devices for the instance
  blockDeviceMappings:
    - deviceName: /dev/xvda
      ebs:
        volumeSize: 100Gi
        volumeType: gp3
        iops: 10000
        encrypted: true
        kmsKeyID: "1234abcd-12ab-34cd-56ef-1234567890ab"
        deleteOnTermination: true
        throughput: 125
        snapshotID: snap-0123456789

  # Optional, configures detailed monitoring for the instance
  detailedMonitoring: true

  # Optional, configures if the instance should be launched with an associated public IP address.
  # If not specified, the default value depends on the subnet's public IP auto-assign setting.
  associatePublicIPAddress: true
status:
  # Resolved subnets
  subnets:
    - id: subnet-0a462d98193ff9fac
      zone: us-east-2b
    - id: subnet-0322dfafd76a609b6
      zone: us-east-2c
    - id: subnet-0727ef01daf4ac9fe
      zone: us-east-2b
    - id: subnet-00c99aeafe2a70304
      zone: us-east-2a
    - id: subnet-023b232fd5eb0028e
      zone: us-east-2c
    - id: subnet-03941e7ad6afeaa72
      zone: us-east-2a

  # Resolved security groups
  securityGroups:
    - id: sg-041513b454818610b
      name: ClusterSharedNodeSecurityGroup
    - id: sg-0286715698b894bca
      name: ControlPlaneSecurityGroup-1AQ073TSAAPW

  # Resolved AMIs
  amis:
    - id: ami-01234567890123456
      name: custom-ami-amd64
      requirements:
        - key: kubernetes.io/arch
          operator: In
          values:
            - amd64
    - id: ami-01234567890123456
      name: custom-ami-arm64
      requirements:
        - key: kubernetes.io/arch
          operator: In
          values:
            - arm64

  # Generated instance profile name from "role"
  instanceProfile: "${CLUSTER_NAME}-0123456778901234567789"

Refer to the NodePool docs for settings applicable to all providers. To explore various EC2NodeClass configurations, refer to the examples provided in the Karpenter Github repository.

spec.amiFamily

AMIFamily is a required field, dictating both the default bootstrapping logic for nodes provisioned through this EC2NodeClass but also selecting a group of recommended, latest AMIs by default. Currently, Karpenter supports amiFamily values AL2, AL2023, Bottlerocket, Ubuntu, Windows2019, Windows2022 and Custom. GPUs are only supported by default with AL2 and Bottlerocket. The AL2 amiFamily does not support ARM64 GPU instance types unless you specify custom amiSelectorTerms. Default bootstrapping logic is shown below for each of the supported families.

AL2

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

--//
Content-Type: text/x-shellscript; charset="us-ascii"

#!/bin/bash -xe
exec > >(tee /var/log/user-data.log|logger -t user-data -s 2>/dev/console) 2>&1
/etc/eks/bootstrap.sh 'test-cluster' --apiserver-endpoint 'https://test-cluster' --b64-cluster-ca 'ca-bundle' \
--dns-cluster-ip '10.100.0.10' \
--use-max-pods false \
--kubelet-extra-args '--node-labels=karpenter.sh/capacity-type=on-demand,karpenter.sh/nodepool=test  --max-pods=110'
--//--

AL2023

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

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

# Karpenter Generated NodeConfig
apiVersion: node.eks.aws/v1alpha1
kind: NodeConfig
spec:
  cluster:
    name: test-cluster
    apiServerEndpoint: https://example.com
    certificateAuthority: ca-bundle
    cidr: 10.100.0.0/16
  kubelet:
    config:
      maxPods: 110
    flags:
      - --node-labels=karpenter.sh/capacity-type=on-demand,karpenter.sh/nodepool=test

--//--

Bottlerocket

[settings]
[settings.kubernetes]
api-server = 'https://test-cluster'
cluster-certificate = 'ca-bundle'
cluster-name = 'test-cluster'
cluster-dns-ip = '10.100.0.10'
max-pods = 110

[settings.kubernetes.node-labels]
'karpenter.sh/capacity-type' = 'on-demand'
'karpenter.sh/nodepool' = 'test'

Ubuntu

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

--//
Content-Type: text/x-shellscript; charset="us-ascii"

#!/bin/bash -xe
exec > >(tee /var/log/user-data.log|logger -t user-data -s 2>/dev/console) 2>&1
/etc/eks/bootstrap.sh 'test-cluster' --apiserver-endpoint 'https://test-cluster' --b64-cluster-ca 'ca-bundle' \
--dns-cluster-ip '10.100.0.10' \
--use-max-pods false \
--kubelet-extra-args '--node-labels="karpenter.sh/capacity-type=on-demand,karpenter.sh/nodepool=test" --max-pods=110'
--//--

Windows2019

<powershell>
[string]$EKSBootstrapScriptFile = "$env:ProgramFiles\Amazon\EKS\Start-EKSBootstrap.ps1"
& $EKSBootstrapScriptFile -EKSClusterName 'test-cluster' -APIServerEndpoint 'https://test-cluster' -Base64ClusterCA 'ca-bundle' -KubeletExtraArgs '--node-labels="karpenter.sh/capacity-type=on-demand,karpenter.sh/nodepool=test" --max-pods=110' -DNSClusterIP '10.100.0.10'
</powershell>

Windows2022

<powershell>
[string]$EKSBootstrapScriptFile = "$env:ProgramFiles\Amazon\EKS\Start-EKSBootstrap.ps1"
& $EKSBootstrapScriptFile -EKSClusterName 'test-cluster' -APIServerEndpoint 'https://test-cluster' -Base64ClusterCA 'ca-bundle' -KubeletExtraArgs '--node-labels="karpenter.sh/capacity-type=on-demand,karpenter.sh/nodepool=test" --max-pods=110' -DNSClusterIP '10.100.0.10'
</powershell>

Custom

The Custom AMIFamily ships without any default userData to allow you to configure custom bootstrapping for control planes or images that don’t support the default methods from the other families.

spec.subnetSelectorTerms

Subnet Selector Terms allow you to specify selection logic for a set of subnet options that Karpenter can choose from when launching an instance from the EC2NodeClass. Karpenter discovers subnets through the EC2NodeClass using ids or tags. When launching nodes, a subnet is automatically chosen that matches the desired zone. If multiple subnets exist for a zone, the one with the most available IP addresses will be used.

This selection logic is modeled as terms, where each term contains multiple conditions that must all be satisfied for the selector to match. Effectively, all requirements within a single term are ANDed together. It’s possible that you may want to select on two different subnets that have unrelated requirements. In this case, you can specify multiple terms which will be ORed together to form your selection logic. The example below shows how this selection logic is fulfilled.

subnetSelectorTerms:
  # Select on any subnet that has the "karpenter.sh/discovery: ${CLUSTER_NAME}"
  # AND the "environment: test" tag OR any subnet with ID "subnet-09fa4a0a8f233a921"
  - tags:
      karpenter.sh/discovery: "${CLUSTER_NAME}"
      environment: test
  - id: subnet-09fa4a0a8f233a921

Examples

Select all with a specified tag key:

spec:
  subnetSelectorTerms:
    - tags:
        karpenter.sh/discovery/MyClusterName: '*'

Select by name and tag (all criteria must match):

spec:
  subnetSelectorTerms:
    - tags:
        Name: my-subnet
        MyTag: '' # matches all resources with the tag

Select using multiple tag terms:

spec:
  subnetSelectorTerms:
    - tags:
        Name: "my-subnet-1"
    - tags:
        Name: "my-subnet-2"

Select using wildcards:

spec:
  subnetSelectorTerms:
    - tags:
        Name: "*Public*"

Select using ids:

spec:
  subnetSelectorTerms:
    - id: "subnet-09fa4a0a8f233a921"
    - id: "subnet-0471ca205b8a129ae"

spec.securityGroupSelectorTerms

Security Group Selector Terms allow you to specify selection logic for all security groups that will be attached to an instance launched from the EC2NodeClass. The security group of an instance is comparable to a set of firewall rules. EKS creates at least two security groups by default.

This selection logic is modeled as terms, where each term contains multiple conditions that must all be satisfied for the selector to match. Effectively, all requirements within a single term are ANDed together. It’s possible that you may want to select on two different security groups that have unrelated requirements. In this case, you can specify multiple terms which will be ORed together to form your selection logic. The example below shows how this selection logic is fulfilled.

securityGroupSelectorTerms:
  # Select on any security group that has both the "karpenter.sh/discovery: ${CLUSTER_NAME}" tag
  # AND the "environment: test" tag OR any security group with the "my-security-group" name
  # OR any security group with ID "sg-063d7acfb4b06c82c"
  - tags:
      karpenter.sh/discovery: "${CLUSTER_NAME}"
      environment: test
  - name: my-security-group
  - id: sg-063d7acfb4b06c82c

Examples

Select all assigned to a cluster:

spec:
  securityGroupSelectorTerms:
    - tags:
        kubernetes.io/cluster/$CLUSTER_NAME: "owned"

Select all with a specified tag key:

spec:
  securityGroupSelectorTerms:
    - tags:
        MyTag: '*'

Select by name and tag (all criteria must match):

spec:
  securityGroupSelectorTerms:
    - name: my-security-group
      tags:
        MyTag: '*' # matches all resources with the tag

Select using multiple tag terms:

spec:
  securityGroupSelectorTerms:
    - tags:
        Name: "my-security-group-1"
    - tags:
        Name: "my-security-group-2"

Select by name using a wildcard:

spec:
  securityGroupSelectorTerms:
    - name: "*Public*"

Select using ids:

spec:
 securityGroupSelectorTerms:
    - id: "sg-063d7acfb4b06c82c"
    - id: "sg-06e0cf9c198874591"

spec.amiSelectorTerms

AMI Selector Terms are used to configure custom AMIs for Karpenter to use, where the AMIs are discovered through ids, owners, name, and tags. When you specify amiSelectorTerms, you fully override the default AMIs that are selected on by your EC2NodeClass amiFamily.

This selection logic is modeled as terms, where each term contains multiple conditions that must all be satisfied for the selector to match. Effectively, all requirements within a single term are ANDed together. It’s possible that you may want to select on two different AMIs that have unrelated requirements. In this case, you can specify multiple terms which will be ORed together to form your selection logic. The example below shows how this selection logic is fulfilled.

amiSelectorTerms:
  # Select on any AMI that has both the "karpenter.sh/discovery: ${CLUSTER_NAME}" tag
  # AND the "environment: test" tag OR any AMI with the "my-ami" name
  # OR any AMI with ID "ami-123"
  - tags:
      karpenter.sh/discovery: "${CLUSTER_NAME}"
      environment: test
  - name: my-ami
  - id: ami-123

This field is optional, and Karpenter will use the latest EKS-optimized AMIs for the AMIFamily if no amiSelectorTerms are specified. To select an AMI by name, use the name field in the selector term. To select an AMI by id, use the id field in the selector term. To ensure that AMIs are owned by the expected owner, use the owner field - you can use a combination of account aliases (e.g. self amazon, your-aws-account-name) and account IDs.

If owner is not set for name, it defaults to self,amazon, preventing Karpenter from inadvertently selecting an AMI that is owned by a different account. Tags don’t require an owner as tags can only be discovered by the user who created them.

Examples

Select all with a specified tag:

  amiSelectorTerms:
    - tags:
        karpenter.sh/discovery/MyClusterName: '*'

Select by name:

  amiSelectorTerms:
    - name: my-ami

Select by Name tag:

  amiSelectorTerms:
    - tags:
        Name: my-ami

Select by name and owner:

  amiSelectorTerms:
    - name: my-ami
      owner: self
    - name: my-ami
      owner: 0123456789

Select by name using a wildcard:

spec:
  amiSelectorTerms:
    - name: "*EKS*"

Select by all under an owner:

spec:
  amiSelectorTerms:
    - name: "*"
      owner: self

Specify using ids:

  amiSelectorTerms:
    - id: "ami-123"
    - id: "ami-456"

spec.role

Role is an optional field and tells Karpenter which IAM identity nodes should assume. You must specify one of role or instanceProfile when creating a Karpenter EC2NodeClass. If using the Karpenter Getting Started Guide to deploy Karpenter, you can use the KarpenterNodeRole-$CLUSTER_NAME role provisioned by that process.

spec:
  role: "KarpenterNodeRole-$CLUSTER_NAME"

spec.instanceProfile

InstanceProfile is an optional field and tells Karpenter which IAM identity nodes should assume. You must specify one of role or instanceProfile when creating a Karpenter EC2NodeClass. If you use the instanceProfile field instead of role, Karpenter will not manage the InstanceProfile on your behalf; instead, it expects that you have pre-provisioned an IAM instance profile and assigned it a role.

You can provision and assign a role to an IAM instance profile using CloudFormation or by using the aws iam create-instance-profile and aws iam add-role-to-instance-profile commands in the CLI.

spec.tags

Karpenter adds tags to all resources it creates, including EC2 Instances, EBS volumes, and Launch Templates. The default set of tags are listed below.

Name: <node-name>
karpenter.sh/nodeclaim: <nodeclaim-name>
karpenter.sh/nodepool: <nodepool-name>
karpenter.k8s.aws/ec2nodeclass: <ec2nodeclass-name>
kubernetes.io/cluster/<cluster-name>: owned

Additional tags can be added in the tags section, which will be merged with the default tags specified above.

spec:
  tags:
    InternalAccountingTag: 1234
    dev.corp.net/app: Calculator
    dev.corp.net/team: MyTeam

spec.metadataOptions

Control the exposure of Instance Metadata Service on EC2 Instances launched by this EC2NodeClass using a generated launch template.

Refer to recommended, security best practices for limiting exposure of Instance Metadata and User Data to pods.

If metadataOptions are omitted from this EC2NodeClass, the following default settings are applied:

spec:
  metadataOptions:
    httpEndpoint: enabled
    httpProtocolIPv6: disabled
    httpPutResponseHopLimit: 2
    httpTokens: required

spec.blockDeviceMappings

The blockDeviceMappings field in an EC2NodeClass can be used to control the Elastic Block Storage (EBS) volumes that Karpenter attaches to provisioned nodes. Karpenter uses default block device mappings for the AMIFamily specified. For example, the Bottlerocket AMI Family defaults with two block device mappings, one for Bottlerocket’s control volume and the other for container resources such as images and logs.

spec:
  blockDeviceMappings:
    - deviceName: /dev/xvda
      ebs:
        volumeSize: 100Gi
        volumeType: gp3
        iops: 10000
        encrypted: true
        kmsKeyID: "1234abcd-12ab-34cd-56ef-1234567890ab"
        deleteOnTermination: true
        throughput: 125
        snapshotID: snap-0123456789

The following blockDeviceMapping defaults are used for each AMIFamily if no blockDeviceMapping overrides are specified in the EC2NodeClass

AL2

spec:
  blockDeviceMappings:
    - deviceName: /dev/xvda
      ebs:
        volumeSize: 20Gi
        volumeType: gp3
        encrypted: true

AL2023

spec:
  blockDeviceMappings:
    - deviceName: /dev/xvda
      ebs:
        volumeSize: 20Gi
        volumeType: gp3
        encrypted: true

Bottlerocket

spec:
  blockDeviceMappings:
    # Root device
    - deviceName: /dev/xvda
      ebs:
        volumeSize: 4Gi
        volumeType: gp3
        encrypted: true
    # Data device: Container resources such as images and logs
    - deviceName: /dev/xvdb
      ebs:
        volumeSize: 20Gi
        volumeType: gp3
        encrypted: true

Ubuntu

spec:
  blockDeviceMappings:
    - deviceName: /dev/sda1
      ebs:
        volumeSize: 20Gi
        volumeType: gp3
        encrypted: true

Windows2019/Windows2022

spec:
  blockDeviceMappings:
    - deviceName: /dev/sda1
      ebs:
        volumeSize: 50Gi
        volumeType: gp3
        encrypted: true

Custom

The Custom AMIFamily ships without any default blockDeviceMappings.

spec.instanceStorePolicy

The instanceStorePolicy field controls how instance-store volumes are handled. By default, Karpenter and Kubernetes will simply ignore them.

RAID0

If you intend to use these volumes for faster node ephemeral-storage, set instanceStorePolicy to RAID0:

spec:
  instanceStorePolicy: RAID0

This will set the allocatable ephemeral-storage of each node to the total size of the instance-store volume(s).

The disks must be formatted & mounted in a RAID0 and be the underlying filesystem for the Kubelet & Containerd. Instructions for each AMI family are listed below:

AL2

On AL2, Karpenter automatically configures the disks through an additional boostrap argument (--local-disks raid0). The device name is /dev/md/0 and its mount point is /mnt/k8s-disks/0. You should ensure any additional disk setup does not interfere with these.

AL2023

On AL2023, Karpenter automatically configures the disks via the generated NodeConfig object. Like AL2, the device name is /dev/md/0 and its mount point is /mnt/k8s-disks/0. You should ensure any additional disk setup does not interfere with these.

Others

For all other AMI families, you must configure the disks yourself. Check out the setup-local-disks script in amazon-eks-ami to see how this is done for AL2.

spec.userData

You can control the UserData that is applied to your worker nodes via this field. This allows you to run custom scripts or pass-through custom configuration to Karpenter instances on start-up.

apiVersion: karpenter.k8s.aws/v1beta1
kind: EC2NodeClass
metadata:
  name: bottlerocket-example
spec:
  ...
  amiFamily: Bottlerocket
  userData:  |
    [settings.kubernetes]
    "kube-api-qps" = 30
    "shutdown-grace-period" = "30s"
    "shutdown-grace-period-for-critical-pods" = "30s"
    [settings.kubernetes.eviction-hard]
    "memory.available" = "20%"    

This example adds SSH keys to allow remote login to the node (replace my-authorized_keys with your key file):

apiVersion: karpenter.k8s.aws/v1beta1
kind: EC2NodeClass
metadata:
  name: al2-example
spec:
  ...
  amiFamily: AL2
  userData: |
    #!/bin/bash
    mkdir -p ~ec2-user/.ssh/
    touch ~ec2-user/.ssh/authorized_keys
    cat >> ~ec2-user/.ssh/authorized_keys <<EOF
    {{ insertFile "../my-authorized_keys" | indent 4  }}
    EOF
    chmod -R go-w ~ec2-user/.ssh/authorized_keys
    chown -R ec2-user ~ec2-user/.ssh    

For more examples on configuring fields for different AMI families, see the examples here.

Karpenter will merge the userData you specify with the default userData for that AMIFamily. See the AMIFamily section for more details on these defaults. View the sections below to understand the different merge strategies for each AMIFamily.

AL2/Ubuntu

  • Your UserData can be in the MIME multi part archive format.
  • Karpenter will transform your custom user-data as a MIME part, if necessary, and then merge a final MIME part to the end of your UserData parts which will bootstrap the worker node. Karpenter will have full control over all the parameters being passed to the bootstrap script.
    • Karpenter will continue to set MaxPods, ClusterDNS and all other parameters defined in spec.kubeletConfiguration as before.

Consider the following example to understand how your custom UserData will be merged -

Passed-in UserData (bash)

#!/bin/bash
echo "Running custom user data script (bash)"

Merged UserData (bash)

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

--//
Content-Type: text/x-shellscript; charset="us-ascii"

#!/bin/bash
echo "Running custom user data script (bash)"

--//
Content-Type: text/x-shellscript; charset="us-ascii"

#!/bin/bash -xe
exec > >(tee /var/log/user-data.log|logger -t user-data -s 2>/dev/console) 2>&1
/etc/eks/bootstrap.sh 'test-cluster' --apiserver-endpoint 'https://test-cluster' --b64-cluster-ca 'ca-bundle' \
--use-max-pods false \
--kubelet-extra-args '--node-labels=karpenter.sh/capacity-type=on-demand,karpenter.sh/nodepool=test  --max-pods=110'
--//--

Passed-in UserData (MIME)

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

--BOUNDARY
Content-Type: text/x-shellscript; charset="us-ascii"

#!/bin/bash
echo "Running custom user data script (mime)"

--BOUNDARY--

Merged UserData (MIME)

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

--//
Content-Type: text/x-shellscript; charset="us-ascii"

#!/bin/bash
echo "Running custom user data script (mime)"

--//
Content-Type: text/x-shellscript; charset="us-ascii"

#!/bin/bash -xe
exec > >(tee /var/log/user-data.log|logger -t user-data -s 2>/dev/console) 2>&1
/etc/eks/bootstrap.sh 'test-cluster' --apiserver-endpoint 'https://test-cluster' --b64-cluster-ca 'ca-bundle' \
--use-max-pods false \
--kubelet-extra-args '--node-labels=karpenter.sh/capacity-type=on-demand,karpenter.sh/nodepool=test  --max-pods=110'
--//--

AL2023

  • Your UserData may be in one of three formats: a MIME multi part archive, a NodeConfig YAML / JSON string, or a shell script.
  • Karpenter will transform your custom UserData into a MIME part, if necessary, and then create a MIME multi-part archive. This archive will consist of a generated NodeConfig, containing Karpenter’s default values, followed by the transformed custom UserData. For more information on the NodeConfig spec, refer to the AL2023 EKS Optimized AMI docs.
  • If a value is specified both in the Karpenter generated NodeConfig and the same value is specified in the custom user data, the value in the custom user data will take precedence.

Passed-in UserData (NodeConfig)

apiVersion: node.eks.aws/v1alpha1
kind: NodeConfig
spec:
  kubelet:
    config:
      maxPods: 42

Merged UserData (NodeConfig)

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

--//
# Karpenter Generated NodeConfig
Content-Type: application/node.eks.aws

# Karpenter Generated NodeConfig
apiVersion: node.eks.aws/v1alpha1
kind: NodeConfig
spec:
  cluster:
    apiServerEndpoint: https://test-cluster
    certificateAuthority: cluster-ca
    cidr: 10.100.0.0/16
    name: test-cluster
  kubelet:
    config:
      clusterDNS:
      - 10.100.0.10
      maxPods: 118
    flags:
    - --node-labels="karpenter.sh/capacity-type=on-demand,karpenter.sh/nodepool=default"

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

apiVersion: node.eks.aws/v1alpha1
kind: NodeConfig
spec:
  kubelet:
    config:
      maxPods: 42
--//--

Passed-in UserData (bash)

#!/bin/bash
echo "Hello, AL2023!"

Merged UserData (bash)

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

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

# Karpenter Generated NodeConfig
apiVersion: node.eks.aws/v1alpha1
kind: NodeConfig
spec:
  cluster:
    apiServerEndpoint: https://test-cluster
    certificateAuthority: cluster-ca
    cidr: 10.100.0.0/16
    name: test-cluster
  kubelet:
    config:
      clusterDNS:
      - 10.100.0.10
      maxPods: 118
    flags:
    - --node-labels="karpenter.sh/capacity-type=on-demand,karpenter.sh/nodepool=default"

--//
Content-Type: text/x-shellscript; charset="us-ascii"

#!/bin/bash
echo "Hello, AL2023!"
--//--

Passed-in UserData (MIME)

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

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

apiVersion: node.eks.aws/v1alpha1
kind: NodeConfig
spec:
  kubelet:
    config:
      maxPods: 42
--//
Content-Type: text/x-shellscript; charset="us-ascii"

#!/bin/bash
echo "Hello, AL2023!"
--//

Merged UserData (MIME)

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

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

# Karpenter Generated NodeConfig
apiVersion: node.eks.aws/v1alpha1
kind: NodeConfig
spec:
  cluster:
    apiServerEndpoint: https://test-cluster
    certificateAuthority: cluster-ca
    cidr: 10.100.0.0/16
    name: test-cluster
  kubelet:
    config:
      clusterDNS:
      - 10.100.0.10
      maxPods: 118
    flags:
    - --node-labels="karpenter.sh/capacity-type=on-demand,karpenter.sh/nodepool=default"

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

apiVersion: node.eks.aws/v1alpha1
kind: NodeConfig
spec:
  kubelet:
    config:
      maxPods: 42
--//
Content-Type: text/x-shellscript; charset="us-ascii"

#!/bin/bash
echo "Hello, AL2023!"
--//--

Bottlerocket

  • Your UserData must be valid TOML.
  • Karpenter will automatically merge settings to ensure successful bootstrap including cluster-name, api-server and cluster-certificate. Any labels and taints that need to be set based on pod requirements will also be specified in the final merged UserData.
    • All Kubelet settings that Karpenter applies will override the corresponding settings in the provided UserData. For example, if you’ve specified settings.kubernetes.cluster-name, it will be overridden.
    • If MaxPods is specified via the binary arg to Karpenter, the value will override anything specified in the UserData.
    • If ClusterDNS is specified via spec.kubeletConfiguration, then that value will override anything specified in the UserData.
  • Unknown TOML fields will be ignored when the final merged UserData is generated by Karpenter.

Consider the following example to understand how your custom UserData settings will be merged in.

Passed-in UserData

[settings.kubernetes.eviction-hard]
"memory.available" = "12%"
[settings.kubernetes]
"unknown-setting" = "unknown"
[settings.kubernetes.node-labels]
'field.controlled.by/karpenter' = 'will-be-overridden'

Merged UserData

[settings]
[settings.kubernetes]
api-server = 'https://cluster'
cluster-certificate = 'ca-bundle'
cluster-name = 'cluster'

[settings.kubernetes.node-labels]
'karpenter.sh/capacity-type' = 'on-demand'
'karpenter.sh/nodepool' = 'default'

[settings.kubernetes.node-taints]

[settings.kubernetes.eviction-hard]
'memory.available' = '12%%'

Windows2019/Windows2022

  • Your UserData must be specified as PowerShell commands.
  • The UserData specified will be prepended to a Karpenter managed section that will bootstrap the kubelet.
  • Karpenter will continue to set ClusterDNS and all other parameters defined in spec.kubeletConfiguration as before.

Consider the following example to understand how your custom UserData settings will be merged in.

Passed-in UserData

Write-Host "Running custom user data script"

Merged UserData

<powershell>
Write-Host "Running custom user data script"
[string]$EKSBootstrapScriptFile = "$env:ProgramFiles\Amazon\EKS\Start-EKSBootstrap.ps1"
& $EKSBootstrapScriptFile -EKSClusterName 'test-cluster' -APIServerEndpoint 'https://test-cluster' -Base64ClusterCA 'ca-bundle' -KubeletExtraArgs '--node-labels="karpenter.sh/capacity-type=spot,karpenter.sh/nodepool=windows2022" --max-pods=110' -DNSClusterIP '10.0.100.10'
</powershell>

Custom

  • No merging is performed, your UserData must perform all setup required of the node to allow it to join the cluster.

spec.detailedMonitoring

Enabling detailed monitoring controls the EC2 detailed monitoring feature. If you enable this option, the Amazon EC2 console displays monitoring graphs with a 1-minute period for the instances that Karpenter launches.

spec:
  detailedMonitoring: true

spec.associatePublicIPAddress

A boolean field that controls whether instances created by Karpenter for this EC2NodeClass will have an associated public IP address. This overrides the MapPublicIpOnLaunch setting applied to the subnet the node is launched in. If this field is not set, the MapPublicIpOnLaunch field will be respected.

status.subnets

status.subnets contains the resolved id and zone of the subnets that were selected by the spec.subnetSelectorTerms for the node class. The subnets will be sorted by the available IP address count in decreasing order.

Examples

spec:
  subnetSelectorTerms:
    - tags:
        karpenter.sh/discovery: "${CLUSTER_NAME}"
status:
  subnets:
  - id: subnet-0a462d98193ff9fac
    zone: us-east-2b
  - id: subnet-0322dfafd76a609b6
    zone: us-east-2c
  - id: subnet-0727ef01daf4ac9fe
    zone: us-east-2b
  - id: subnet-00c99aeafe2a70304
    zone: us-east-2a
  - id: subnet-023b232fd5eb0028e
    zone: us-east-2c
  - id: subnet-03941e7ad6afeaa72
    zone: us-east-2a

status.securityGroups

status.securityGroups contains the resolved id and name of the security groups that were selected by the spec.securityGroupSelectorTerms for the node class. The subnets will be sorted by the available IP address count in decreasing order.

Examples

spec:
  securityGroupSelectorTerms:
    - tags:
        karpenter.sh/discovery: "${CLUSTER_NAME}"
status:
  securityGroups:
  - id: sg-041513b454818610b
    name: ClusterSharedNodeSecurityGroup
  - id: sg-0286715698b894bca
    name: ControlPlaneSecurityGroup-1AQ073TSAAPW

status.amis

status.amis contains the resolved id, name, and requirements of either the default AMIs for the spec.amiFamily or the AMIs selected by the spec.amiSelectorTerms if this field is specified.

Examples

Default AMIs resolved from the AL2 AMIFamily:

spec:
  amiFamily: AL2
status:
  amis:
  - id: ami-03c3a3dcda64f5b75
    name: amazon-linux-2-gpu
    requirements:
    - key: kubernetes.io/arch
      operator: In
      values:
      - amd64
    - key: karpenter.k8s.aws/instance-gpu-count
      operator: Exists
  - id: ami-03c3a3dcda64f5b75
    name: amazon-linux-2-gpu
    requirements:
    - key: kubernetes.io/arch
      operator: In
      values:
      - amd64
    - key: karpenter.k8s.aws/instance-accelerator-count
      operator: Exists
  - id: ami-06afb2d101cc4b8bd
    name: amazon-linux-2-arm64
    requirements:
    - key: kubernetes.io/arch
      operator: In
      values:
      - arm64
    - key: karpenter.k8s.aws/instance-gpu-count
      operator: DoesNotExist
    - key: karpenter.k8s.aws/instance-accelerator-count
      operator: DoesNotExist
  - id: ami-0e28b76d768af234e
    name: amazon-linux-2
    requirements:
    - key: kubernetes.io/arch
      operator: In
      values:
      - amd64
    - key: karpenter.k8s.aws/instance-gpu-count
      operator: DoesNotExist
    - key: karpenter.k8s.aws/instance-accelerator-count
      operator: DoesNotExist

AMIs resolved from spec.amiSelectorTerms:

spec:
  amiFamily: AL2
  amiSelectorTerms:
    - tags:
        karpenter.sh/discovery: "${CLUSTER_NAME}"
status:
  amis:
  - id: ami-01234567890123456
    name: custom-ami-amd64
    requirements:
    - key: kubernetes.io/arch
      operator: In
      values:
      - amd64
  - id: ami-01234567890123456
    name: custom-ami-arm64
    requirements:
    - key: kubernetes.io/arch
      operator: In
      values:
      - arm64

status.instanceProfile

status.instanceProfile contains the resolved instance profile generated by Karpenter from the spec.role

spec:
  role: "KarpenterNodeRole-${CLUSTER_NAME}"
status:
  instanceProfile: "${CLUSTER_NAME}-0123456778901234567789"

status.conditions

status.conditions indicates EC2NodeClass readiness. This will be Ready when Karpenter successfully discovers AMIs, Instance Profile, Subnets, Cluster CIDR and SecurityGroups for the EC2NodeClass.

spec:
  role: "KarpenterNodeRole-${CLUSTER_NAME}"
status:
  conditions:
    Last Transition Time:  2024-05-06T06:04:45Z
    Message:               Ready
    Reason:                Ready
    Status:                True
    Type:                  Ready

If any of the underlying conditions are not resolved then Status is False and Message indicates the dependency that was not resolved.

spec:
  role: "KarpenterNodeRole-${CLUSTER_NAME}"
status:
  conditions:
    Last Transition Time:  2024-05-06T06:19:46Z
    Message:               unable to resolve instance profile for node class
    Reason:                NodeClassNotReady
    Status:                False
    Type:                  Ready
Last modified May 29, 2024: chore: Release v0.37.0 (#6278) (b95b3cf4)