Authenticate with Azure Container Registry from Azure Kubernetes Service
When you're using Azure Container Registry (ACR) with Azure Kubernetes Service (AKS), an authentication mechanism needs to be established. This article details the recommended configurations for authentication between these two Azure services.
This article assumes that you've already created an AKS cluster and you are able to access the cluster with the
kubectl command-line client.
Grant AKS access to ACR
When you create an AKS cluster, Azure also creates a service principal to support cluster operability with other Azure resources. You can use this auto-generated service principal for authentication with an ACR registry. To do so, you need to create an Azure AD role assignment that grants the cluster's service principal access to the container registry.
Use the following script to grant the AKS-generated service principal pull access to an Azure container registry. Modify the
ACR_* variables for your environment before running the script.
#!/bin/bash AKS_RESOURCE_GROUP=myAKSResourceGroup AKS_CLUSTER_NAME=myAKSCluster ACR_RESOURCE_GROUP=myACRResourceGroup ACR_NAME=myACRRegistry # Get the id of the service principal configured for AKS CLIENT_ID=$(az aks show --resource-group $AKS_RESOURCE_GROUP --name $AKS_CLUSTER_NAME --query "servicePrincipalProfile.clientId" --output tsv) # Get the ACR registry resource id ACR_ID=$(az acr show --name $ACR_NAME --resource-group $ACR_RESOURCE_GROUP --query "id" --output tsv) # Create role assignment az role assignment create --assignee $CLIENT_ID --role acrpull --scope $ACR_ID
Access with Kubernetes secret
In some instances, you might not be able to assign the required role to the auto-generated AKS service principal granting it access to ACR. For example, due to your organization's security model, you might not have sufficient permissions in your Azure Active Directory tenant to assign a role to the AKS-generated service principal. Assigning a role to a service principal requires your Azure AD account to have write permission to your Azure AD tenant. If you don't have permission, you can create a new service principal, then grant it access to the container registry using a Kubernetes image pull secret.
Use the following script to create a new service principal (you'll use its credentials for the Kubernetes image pull secret). Modify the
ACR_NAME variable for your environment before running the script.
#!/bin/bash ACR_NAME=myacrinstance SERVICE_PRINCIPAL_NAME=acr-service-principal # Populate the ACR login server and resource id. ACR_LOGIN_SERVER=$(az acr show --name $ACR_NAME --query loginServer --output tsv) ACR_REGISTRY_ID=$(az acr show --name $ACR_NAME --query id --output tsv) # Create acrpull role assignment with a scope of the ACR resource. SP_PASSWD=$(az ad sp create-for-rbac --name http://$SERVICE_PRINCIPAL_NAME --role acrpull --scopes $ACR_REGISTRY_ID --query password --output tsv) # Get the service principal client id. CLIENT_ID=$(az ad sp show --id http://$SERVICE_PRINCIPAL_NAME --query appId --output tsv) # Output used when creating Kubernetes secret. echo "Service principal ID: $CLIENT_ID" echo "Service principal password: $SP_PASSWD"
You can now store the service principal's credentials in a Kubernetes image pull secret, which your AKS cluster will reference when running containers.
Use the following kubectl command to create the Kubernetes secret. Replace
<acr-login-server> with the fully qualified name of your Azure container registry (it's in the format "acrname.azurecr.io"). Replace
<service-principal-password> with the values you obtained by running the previous script. Replace
<email-address> with any well-formed email address.
kubectl create secret docker-registry acr-auth --docker-server <acr-login-server> --docker-username <service-principal-ID> --docker-password <service-principal-password> --docker-email <email-address>
You can now use the Kubernetes secret in pod deployments by specifying its name (in this case, "acr-auth") in the
apiVersion: apps/v1beta1 kind: Deployment metadata: name: acr-auth-example spec: template: metadata: labels: app: acr-auth-example spec: containers: - name: acr-auth-example image: myacrregistry.azurecr.io/acr-auth-example imagePullSecrets: - name: acr-auth
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