Uredi

Apply automatic security upgrades to Azure Kubernetes Service (AKS) nodes using GitHub Actions

  • Članek

Security updates are a key part of maintaining your AKS cluster's security and compliance with the latest fixes for the underlying OS. These updates include OS security fixes or kernel updates. Some updates require a node reboot to complete the process.

This article shows you how you can automate the update process of AKS nodes using GitHub Actions and Azure CLI to create an update task based on cron that runs automatically.

Note

You can also perform node image upgrades automatically and schedule these upgrades using planned maintenance. For more information, see Automatically upgrade node images.

Before you begin

  • This article assumes you have an existing AKS cluster. If you need an AKS cluster, create one using Azure CLI, Azure PowerShell, or the Azure portal.
  • This article also assumes you have a GitHub account and a profile repository to host your actions. If you don't have a repository, create one with the same name as your GitHub username.
  • You need the Azure CLI version 2.0.59 or later installed and configured. Run az --version to find the version. If you need to install or upgrade, see Install Azure CLI.

Update nodes with az aks upgrade

The az aks upgrade command gives you a zero downtime way to apply updates. The command performs the following actions:

  1. Applies the latest updates to all your cluster's nodes.
  2. Cordons (makes the node unavailable for the scheduling of new workloads) and drains (moves the existent workloads to other node) traffic to the nodes.
  3. Restarts the nodes.
  4. Enables the updated nodes to receive traffic again.

AKS doesn't automatically restart your nodes if you update them using a different method.

Note

Running az aks upgrade with the --node-image-only flag only upgrades the node images. Running the command without the flag upgrades both the node images and the Kubernetes control plane version. For more information, see the docs for managed upgrades on nodes and the docs for cluster upgrades.

All Kubernetes nodes run in a standard Windows or Linux-based Azure virtual machine (VM). The Linux-based VMs use an Ubuntu image with the OS configured to automatically check for updates every night.

When you use the az aks upgrade command, Azure CLI creates a surge of new nodes with the latest security and kernel updates. These new nodes are initially cordoned to prevent any apps from being scheduled to them until the update completes. After the update completes, Azure cordons and drains the older nodes and uncordons the new ones, transferring all the scheduled applications to the new nodes.

This process is better than updating Linux-based kernels manually because Linux requires a reboot when a new kernel update is installed. If you update the OS manually, you also need to reboot the VM, manually cordoning and draining all the apps.

Create a timed GitHub Action

cron is a utility that allows you to run a set of commands, or jobs, on an automated schedule. To create a job to update your AKS nodes on an automated schedule, you need a repository to host your actions. GitHub Actions are usually configured in the same repository as your application, but you can use any repository.

  1. Navigate to your repository on GitHub.

  2. Select Actions.

  3. Select New workflow > Set up a workflow yourself.

  4. Create a GitHub Action named Upgrade cluster node images with a schedule trigger to run every 15 days at 3am. Copy the following code into the YAML:

    name: Upgrade cluster node images
on:
  schedule:
    - cron: '0 3 */15 * *'

  5. Create a job named upgrade-node that runs on an Ubuntu agent and connects to your Azure CLI account to execute the node upgrade command. Copy the following code into the YAML under the on key:

    jobs:
  upgrade-node:
    runs-on: ubuntu-latest

Set up the Azure CLI in the workflow

  1. In the Search Marketplace for Actions bar, search for Azure Login.

  2. Select Azure Login.

    Search results showing two lines, the first action is called 'Azure Login' and the second 'Azure Container Registry Login'

  3. Under Installation, select a version, such as v1.4.6, and copy the installation code snippet.

  4. Add the steps key and the following information from the installation code snippet to the YAML:

    name: Upgrade cluster node images
on:
  schedule:
    - cron: '0 3 */15 * *'
jobs:
  upgrade-node:
    runs-on: ubuntu-latest
    steps:
      - name: Azure Login
        uses: Azure/login@v1.4.6
        with:
          creds: ${{ secrets.AZURE_CREDENTIALS }}

Create credentials for the Azure CLI

  1. In a new browser window, create a new service principal using the az ad sp create-for-rbac command. Make sure you replace *{subscriptionID}* with your own subscription ID.

    Note

    This example creates the Contributor role at the Subscription scope. You can provide the role and scope that meets your needs. For more information, see Azure built-in roles and Azure RBAC scope levels.

    az ad sp create-for-rbac --role Contributor --scopes /subscriptions/{subscriptionID} -o json

    Your output should be similar to the following example output:

    {
  "appId": "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx",
  "displayName": "xxxxx-xxx-xxxx-xx-xx-xx-xx-xx",
  "password": "xxxxxxxxxxxxxxxxxxxxxxxxxxxx",
  "tenant": "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
}

  2. Copy the output and navigate to your GitHub repository.

  3. Select Settings > Secrets and variables > Actions > New repository secret.

  4. For Name, enter AZURE_CREDENTIALS.

  5. For Secret, copy in the contents of the output you received when you created the service principal.

  6. Select Add Secret.

Create the steps to execute the Azure CLI commands

  1. Navigate to your window with the workflow YAML.

  2. In the Search Marketplace for Actions bar, search for Azure CLI Action.

  3. Select Azure CLI Action.

    Search result for 'Azure CLI Action' with first result being shown as made by Azure

  4. Under Installation, select a version, such as v1.0.8, and copy the installation code snippet.

  5. Paste the contents of the action into the YAML below the *Azure Login* step, similar to the following example:

    name: Upgrade cluster node images
on:
  schedule:
    - cron: '0 3 */15 * *'
jobs:
  upgrade-node:
    runs-on: ubuntu-latest
    steps:
      - name: Azure Login
        uses: Azure/login@v1.4.6
        with:
          creds: ${{ secrets.AZURE_CREDENTIALS }}
      - name: Upgrade node images
        uses: Azure/cli@v1.0.8
        with:
          inlineScript: az aks upgrade -g {resourceGroupName} -n {aksClusterName} --node-image-only --yes

    Tip

    You can decouple the -g and -n parameters from the command by creating new repository secrets like you did for AZURE_CREDENTIALS.

    If you create secrets for these parameters, you need to replace the {resourceGroupName} and {aksClusterName} placeholders with their secret counterparts. For example, ${{secrets.RESOURCE_GROUP_NAME}} and ${{secrets.AKS_CLUSTER_NAME}}

  6. Rename the YAML to upgrade-node-images.yml.

  7. Select Commit changes..., add a commit message, and then select Commit changes.

Run the GitHub Action manually

You can run the workflow manually in addition to the scheduled run by adding a new on trigger called workflow_dispatch.

Note

If you want to upgrade a single node pool instead of all node pools on the cluster, add the --name parameter to the az aks nodepool upgrade command to specify the node pool name. For example:

az aks nodepool upgrade -g {resourceGroupName} --cluster-name {aksClusterName} --name {{nodePoolName}} --node-image-only

  • Add the workflow_dispatch trigger under the on key:

    name: Upgrade cluster node images
on:
  schedule:
    - cron: '0 3 */15 * *'
  workflow_dispatch:

    The YAML should look similar to the following example:

        name: Upgrade cluster node images
    on:
      schedule:
        - cron: '0 3 */15 * *'
      workflow_dispatch:
    jobs:
      upgrade-node:
        runs-on: ubuntu-latest
        steps:
          - name: Azure Login
            uses: Azure/login@v1.4.6
            with:
              creds: ${{ secrets.AZURE_CREDENTIALS }}
          - name: Upgrade node images
            uses: Azure/cli@v1.0.8
            with:
              inlineScript: az aks upgrade -g {resourceGroupName} -n {aksClusterName} --node-image-only --yes
          # Code for upgrading one or more node pools

Next steps

For more information about AKS upgrades, see the following articles and resources:

For a detailed discussion of upgrade best practices and other considerations, see AKS patch and upgrade guidance.