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Node images in Azure Kubernetes Service (AKS)

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This article describes the node images available for Azure Kubernetes Service (AKS) nodes.

Caution

In this article, there are references to Ubuntu OS versions that are being deprecated for AKS.

  • Starting on 17 June 2025, AKS will no longer support Ubuntu 18.04. Existing node images will be deleted and AKS will no longer provide security updates. You'll no longer be able to scale your node pools. Upgrade your node pools to a supported kubernetes version to migrate to a supported Ubuntu version.
  • Starting on 17 March 2027, AKS will no longer support Ubuntu 20.04. Existing node images will be deleted and AKS will no longer provide security updates. You'll no longer be able to scale your node pools. Upgrade your node pools to kubernetes version 1.34+ to migrate to a supported Ubuntu version. For more information on this retirement, see AKS GitHub Issues

Node image releases

Azure Kubernetes Service (AKS) regularly provides new node images, so it's beneficial to upgrade your node images frequently to access the latest AKS features, component updates, and security fixes. You can find detailed summaries of each node image version in the AKS VHD notes.

Linux node images are released weekly, and Windows node images are released monthly. New node images are included in the AKS release notes.

Best practice guidance

Configure automatic node image upgrades and schedule them using planned maintenance. This will ensure that your node images are always up to date without requiring manual upgrades.

When new node images are released, it can take up to two weeks for the updates to be rolled out across all regions. The AKS Release Tracker shows the current latest node image version, three previously available node image versions for each region, and the node image update order by region. Once the node image is available in your region, you can perform a manual node image upgrade or configure automatic node image upgrades and schedule them using planned maintenance.

Default node images

AKS sets a default operating system (OS) and node image during cluster and node pool creation. OS Type can be used to filter between Linux or Windows.

OS Type Default OS Default node image
Not Specified Ubuntu Linux Ubuntu with containerd and gen 2
Linux Ubuntu Linux Ubuntu with containerd and gen 2
Windows Windows Server Windows Server Long Term Servicing Channel (LTSC) with containerd and gen 1

Note

You can't specify the Windows OS Type during cluster creation since the system node pool in every cluster must be Linux.

Supported OS versions

Each node image corresponds to an OS version which you can specify using OS SKU. You specify the following parameters when creating clusters and node pools:

  • --os-type: OS type, including Linux or Windows.
  • --os-sku: Used to specify OS version or OS variant.
  • --kubernetes-version: Version of Kubernetes to use for creating the node pool or cluster.

Best practice guidance

The default OS version is the most recent validated version.

  • For Ubuntu, we recommend creating clusters and node pools while specifying --os-type Linux and --os-sku Ubuntu. This will automatically update you to the latest default Ubuntu version based on your Kubernetes version.
  • For Azure Linux, we recommend creating clusters and node pools while specifying --os-type Linux and --os-sku AzureLinux. This will automatically update you to the latest default Azure Linux version based on your Kubernetes version.
  • For Windows, we recommend creating node pools while specifying --os-type Windows and --os-sku Windows2022. You will need to manually update node pools to the next OS version when it's released.
OS Type OS SKU Supported Kubernetes versions Default versioning
Linux Ubuntu This OS SKU is supported in all Kubernetes versions. OS version for this OS SKU changes based on your Kubernetes version. Ubuntu 22.04 is default for Kubernetes version 1.25 to 1.32.
Linux Azure Linux This OS SKU is supported in all Kubernetes versions. OS version for this OS SKU changes based on your Kubernetes version. Azure Linux 2.0 is default for Kubernetes version 1.27 to 1.31. Azure Linux 3.0 is default for Kubernetes version 1.32+.
Windows Windows2019 1.14-1.32 Default for Windows OS Type in Kubernetes version 1.14 to 1.24.
Windows Windows2022 1.23 to 1.34 Default for Windows OS Type in Kubernetes version 1.25 to 1.33.

Factors that might impact default node images

The following factors might impact the default image AKS chooses for your node pool:

  • OS SKU: If --os-sku is specified, then your default OS changes. For example, if you specify Azure Linux as the OS SKU, then your node image is Azure Linux with containerd.
  • Virtual machine (VM) size:
  • Hypervisor Generation: Each VM size supports Generation 1, Generation 2, or both.
    • If a Generation 2 is supported, AKS defaults to using the Generation 2 node image.
    • If only Generation 1 is supported, AKS defaults to using the Generation 1 node image.
  • Feature enablement: There are some features embedded into the node image. If you choose to use any of these features, your default node image changes.

Note

Certain features can't be combined in a single node pool. Follow links to the feature documentation to review the limitations.

Available Linux node images

Ubuntu node images

The Ubuntu node images are fully validated by AKS and supported by Microsoft, Canonical, and the Ubuntu community. AKS won't retire an Ubuntu version before the end of Canonical's support lifecycle.

Node image Use case Limitations
Ubuntu with containerd and Gen 1 This is the standard node image for Ubuntu node pools using a VM size that only supports Generation 1. N/A
Ubuntu with containerd and Gen 2 This is the standard node image for Ubuntu node pools using a VM size that supports Generation 2. If a VM size supports both Generation 1 and Generation 2, this node image is selected. N/A
Ubuntu with containerd and FIPS This is a variant of the default node image for customers that enable Federal Information Processing Standards (FIPS). These images support both Generation 1 and Generation 2. Not yet supported for Ubuntu 22.04+. Can't be combined with Arm64, Trusted Launch, or CVM.
Ubuntu with containerd and Arm64 This is a variant of the default node image for customers that use a VM size that supports Arm64. These images support Generation 2 only. Can't be combined with FIPS, CVM, or Trusted Launch.
Ubuntu with containerd and CVM This is a variant of the default node image for customers that use a Confidential VM size. These images support Generation 2 only. Not yet supported for Ubuntu 22.04+. Can't be combined with FIPS, Arm64, or Trusted Launch.
Ubuntu with containerd and Trusted Launch This is a variant of the default node image for customers that enable Trusted Launch. These images support Generation 2 only. Can't be combined with FIPS, Arm64, or CVM.

Azure Linux node images

The Azure Linux node images are fully validated by AKS and built from source, using a native AKS image.

Node image Use case Limitations
Azure Linux with containerd and Gen 1 This is the standard node image for Azure Linux node pools using a VM size that only supports Generation 1. N/A
Azure Linux with containerd and Gen 2 This is the standard node image for Azure Linux node pools using a VM size that supports Generation 2. If a VM size supports both Generation 1 and Generation 2, node image is selected. N/A
Azure Linux with containerd and FIPS This is a variant of the default node image for customers that enable Federal Information Processing Standards (FIPS). These images support both Generation 1 and Generation 2. Can't be combined with Arm64, Trusted Launch, or Pod Sandboxing.
Azure Linux with containerd and Arm64 This is a variant of the default node image for customers that use a VM size that supports Arm64. These images support Generation 2 only. Can't be combined with FIPS, Trusted Launch, or Pod Sandboxing.
Azure Linux with containerd and Trusted Launch This is a variant of the default node image for customers that enable Trusted Launch. These images support Generation 2 only. Can't be combined with FIPS, Arm64, or Pod Sandboxing.
Azure Linux with containerd and Pod Sandboxing This is a variant of the default node image for customers that enable Pod Sandboxing. These images support Generation 2 only. Can't be combined with FIPS, Arm64, or Trusted Launch.

Available Windows Server node images

The Windows Server node images are fully validated by AKS and supported by Microsoft.

Windows Server Long Term Servicing Channel (LTSC) node images

Node image Use case Limitations
Windows Server with containerd and Gen 1 This is the standard node image for Azure Linux node pools using a VM size that only supports Generation 1. N/A
Windows Server with containerd and Gen 2 This is the standard node image for Azure Linux node pools using a VM size that supports Generation 2. If a VM size supports both Generation 1 and Generation 2, this node image is selected. N/A

Windows Server Annual Channel for Containers (preview) node images

Node image Use case Limitations
Windows Server with containerd and Gen 1 This is the standard node image for Azure Linux node pools using a VM size that only supports Generation 1. N/A
Windows Server with containerd and Gen 2 This is the standard node image for Azure Linux node pools using a VM size that supports Generation 2. If a VM size supports both Generation 1 and Generation 2, this node image is selected. N/A

Next steps

To learn more about node images, node pool upgrades, and node configurations on AKS, see the following resources: