Authenticate with a private Docker container registry
There are several ways to authenticate with an Azure container registry, each of which is applicable to one or more registry usage scenarios.
You can log in to a registry directly via individual login, or your applications and container orchestrators can perform unattended, or "headless," authentication by using an Azure Active Directory (Azure AD) service principal.
Azure Container Registry does not support unauthenticated Docker operations or anonymous access. For public images, you can use Docker Hub.
Individual login with Azure AD
az acr login --name <acrName>
When you log in with
az acr login, the CLI uses the token created when you executed az login to seamlessly authenticate your session with your registry. Once you've logged in this way, your credentials are cached, and subsequent
docker commands do not require a username or password. If your token expires, you can refresh it by using the
az acr login command again to reauthenticate. Using
az acr login with Azure identities provides role-based access.
If you assign a service principal to your registry, your application or service can use it for headless authentication. Service principals allow role-based access to a registry, and you can assign multiple service principals to a registry. Multiple service principals allow you to define different access for different applications.
The available roles for a container registry include:
AcrPush: pull and push
Owner: pull, push, and assign roles to other users
For a complete list of roles, see Azure Container Registry roles and permissions.
For CLI scripts to create a service principal app ID and password for authenticating with an Azure container registry, or to use an existing service principal, see Azure Container Registry authentication with service principals.
Service principals enable headless connectivity to a registry in both pull and push scenarios like the following:
Pull: Deploy containers from a registry to orchestration systems including Kubernetes, DC/OS, and Docker Swarm. You can also pull from container registries to related Azure services such as Azure Kubernetes Service, Azure Container Instances, App Service, Batch, Service Fabric, and others.
Push: Build container images and push them to a registry using continuous integration and deployment solutions like Azure Pipelines or Jenkins.
You can also log in directly with a service principal. Provide the app ID and password of the service principal to the
docker login command:
docker login myregistry.azurecr.io -u <SP_APP_ID> -p <SP_PASSWD>
Once logged in, Docker caches the credentials, so you don't need to remember the app ID.
Depending on the version of Docker you have installed, you might see a security warning recommending the use of the
--password-stdin parameter. While its use is outside the scope of this article, we recommend following this best practice. For more information, see the docker login command reference.
You can regenerate the password of a service principal by running the az ad sp reset-credentials command.
Each container registry includes an admin user account, which is disabled by default. You can enable the admin user and manage its credentials in the Azure portal, or by using the Azure CLI or other Azure tools.
The admin account is designed for a single user to access the registry, mainly for testing purposes. We do not recommend sharing the admin account credentials with multiple users. All users authenticating with the admin account appear as a single user with push and pull access to the registry. Changing or disabling this account disables registry access for all users who use its credentials. Individual identity is recommended for users and service principals for headless scenarios.
The admin account is provided with two passwords, both of which can be regenerated. Two passwords allow you to maintain connection to the registry by using one password while you regenerate the other. If the admin account is enabled, you can pass the username and either password to the
docker login command for basic authentication to the registry. For example:
docker login myregistry.azurecr.io -u myAdminName -p myPassword1
Again, Docker recommends that you use the
--password-stdin parameter instead of supplying it on the command line for increased security. You can also specify only your username, without
-p, and enter your password when prompted.
To enable the admin user for an existing registry, you can use the
--admin-enabled parameter of the az acr update command in the Azure CLI:
az acr update -n <acrName> --admin-enabled true
You can enable the admin user in the Azure portal by navigating your registry, selecting Access keys under SETTINGS, then Enable under Admin user.