Automatically upgrade Azure Kubernetes Service cluster node operating system images (preview)
AKS now supports an exclusive channel dedicated to controlling node-level OS security updates. This channel, referred to as the node OS auto-upgrade channel, works in tandem with the existing auto-upgrade channel, which is used for Kubernetes version upgrades.
AKS preview features are available on a self-service, opt-in basis. Previews are provided "as is" and "as available," and they're excluded from the service-level agreements and limited warranty. AKS previews are partially covered by customer support on a best-effort basis. As such, these features aren't meant for production use. For more information, see the following support articles:
Why use node OS auto-upgrade
This channel is exclusively meant to control node OS security updates. You can use this channel to disable unattended upgrades. You can schedule maintenance without worrying about Kured for security patches, provided you choose either the
NodeImage options for
nodeOSUpgradeChannel. By using this channel, you can run node image upgrades in tandem with Kubernetes version auto-upgrade channels like
Must be using API version
If using Azure CLI, the
aks-previewCLI extension version
0.5.127or later must be installed
If using the
NodeOsUpgradeChannelPreviewfeature flag must be enabled on your subscription
Register the 'NodeOsUpgradeChannelPreview' feature flag
NodeOsUpgradeChannelPreview feature flag by using the az feature register command, as shown in the following example:
az feature register --namespace "Microsoft.ContainerService" --name "NodeOsUpgradeChannelPreview"
It takes a few minutes for the status to show Registered. Verify the registration status by using the az feature show command:
az feature show --namespace "Microsoft.ContainerService" --name "NodeOsUpgradeChannelPreview"
When the status reflects Registered, refresh the registration of the Microsoft.ContainerService resource provider by using the az provider register command:
az provider register --namespace Microsoft.ContainerService
If using the
node-image cluster auto-upgrade channel or the
NodeImage node OS auto-upgrade channel, Linux unattended upgrades are disabled by default. You can't change node OS auto-upgrade channel value if your cluster auto-upgrade channel is
node-image. In order to set the node OS auto-upgrade channel values, make sure the cluster auto-upgrade channel isn't
nodeosupgradechannel isn't supported on Windows OS node pools. Azure Linux support is now rolled out and is expected to be available in all regions soon.
Using node OS auto-upgrade
Automatically completed upgrades are functionally the same as manual upgrades. The selected channel determines the timing of upgrades. When making changes to auto-upgrade, allow 24 hours for the changes to take effect. By default, a cluster's node OS auto-upgrade channel is set to
Node OS image auto-upgrade won't affect the cluster's Kubernetes version, but it still requires the cluster to be in a supported version to function properly.
When changing channels to
SecurityPatch, the unattended upgrades will only be disabled when the image gets applied in the next cycle and not immediately.
The following upgrade channels are available:
||Your nodes won't have security updates applied automatically. This means you're solely responsible for your security updates.||N/A|
||OS updates are applied automatically through the OS built-in patching infrastructure. Newly allocated machines are unpatched initially and will be patched at some point by the OS's infrastructure.||Ubuntu applies security patches through unattended upgrade roughly once a day around 06:00 UTC. Windows doesn't automatically apply security patches, so this option behaves equivalently to
||AKS regularly updates the node's virtual hard disk (VHD) with patches from the image maintainer labeled "security only". There maybe disruptions when the security patches are applied to the nodes. When the patches are applied, the VHD is updated and existing machines are upgraded to that VHD, honoring maintenance windows and surge settings. This option incurs the extra cost of hosting the VHDs in your node resource group. If you use this channel, Linux unattended upgrades are disabled by default.||Azure Linux doesn't support this channel on GPU-enabled VMs.|
||AKS updates the nodes with a newly patched VHD containing security fixes and bug fixes on a weekly cadence. The update to the new VHD is disruptive, following maintenance windows and surge settings. No extra VHD cost is incurred when choosing this option. If you use this channel, Linux unattended upgrades are disabled by default.|
To set the node OS auto-upgrade channel when creating a cluster, use the node-os-upgrade-channel parameter, similar to the following example.
az aks create --resource-group myResourceGroup --name myAKSCluster --node-os-upgrade-channel SecurityPatch
To set the auto-upgrade channel on existing cluster, update the node-os-upgrade-channel parameter, similar to the following example.
az aks update --resource-group myResourceGroup --name myAKSCluster --node-os-upgrade-channel SecurityPatch
Using node OS auto-upgrade with Planned Maintenance
If you’re using Planned Maintenance and node OS auto-upgrade, your upgrade starts during your specified maintenance window.
To ensure proper functionality, use a maintenance window of four hours or more.
For more information on Planned Maintenance, see Use Planned Maintenance to schedule maintenance windows for your Azure Kubernetes Service (AKS) cluster.
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