Lock a container image in an Azure container registry

Article
10/31/2023

In an Azure container registry, you can lock an image version or a repository so that it can't be deleted or updated. To lock an image or a repository, update its attributes using the Azure CLI command az acr repository update.

This article requires that you run the Azure CLI in Azure Cloud Shell or locally (version 2.0.55 or later recommended). Run az --version to find the version. If you need to install or upgrade, see Install Azure CLI.

Important

This article doesn't apply to locking an entire registry, for example, using Settings > Locks in the Azure portal, or az lock commands in the Azure CLI. Locking a registry resource doesn't prevent you from creating, updating, or deleting data in repositories. Locking a registry only affects management operations such as adding or deleting replications, or deleting the registry itself. More information in Lock resources to prevent unexpected changes.

Scenarios

By default, a tagged image in Azure Container Registry is mutable, so with appropriate permissions you can repeatedly update and push an image with the same tag to a registry. Container images can also be deleted as needed. This behavior is useful when you develop images and need to maintain a size for your registry.

However, when you deploy a container image to production, you might need an immutable container image. An immutable image is one that you can't accidentally delete or overwrite.

See Recommendations for tagging and versioning container images for strategies to tag and version images in your registry.

Use the az acr repository update command to set repository attributes so you can:

Lock an image version, or an entire repository
Protect an image version or repository from deletion, but allow updates
Prevent read (pull) operations on an image version, or an entire repository

See the following sections for examples.

Lock an image or repository

Show the current repository attributes

To see the current attributes of a repository, run the following az acr repository show command:

az acr repository show \
    --name myregistry --repository myrepo \
    --output jsonc

Show the current image attributes

To see the current attributes of a tag, run the following az acr repository show command:

az acr repository show \
    --name myregistry --image myrepo:tag \
    --output jsonc

Lock an image by tag

To lock the myrepo:tag image in myregistry, run the following az acr repository update command:

az acr repository update \
    --name myregistry --image myrepo:tag \
    --write-enabled false

Lock an image by manifest digest

To lock a myrepo image identified by manifest digest (SHA-256 hash, represented as sha256:...), run the following command. (To find the manifest digest associated with one or more image tags, run the az acr manifest list-metadata command.)

az acr repository update \
    --name myregistry --image myrepo@sha256:123456abcdefg \
    --write-enabled false

Lock a repository

To lock the myrepo repository and all images in it, run the following command:

az acr repository update \
    --name myregistry --repository myrepo \
    --write-enabled false

List the current repository attributes

To update the repository attributes to indicate image lock listing, run the az acr repository update command.

az acr repository update \
    --name myregistry --repository myrepo \ 
    --list-enabled false

Show the image attributes on image lock

To query the tags on a image lock with --list-enabled false enabled on the attribute, run the az acr repository show command.

az acr repository show-manifests \
    --name myregistry --repository myrepo \
    --query "[?listEnabled==null].tags" 
    --output table

Check image attributes for tag and its corresponding manifest.

Note

The changeable attributes of tags and manifest are managed separately. That is, setting attribute deleteEnabled=false for the tag won't set the same for the corresponding manifest.

Query the attributes using the script below:

registry="myregistry"
repo="myrepo"
tag="mytag"

az login
az acr repository show -n $registry --repository $repo
az acr manifest show-metadata -r $registry -n "$repo:$tag"
digest=$(az acr manifest show-metadata -r $registry -n "$repo:$tag" --query digest -o tsv)
az acr manifest show-metadata -r $registry -n "$repo@$digest"

Note

If the image attributes are set with writeEnabled=false or deleteEnabled=false, then it will block image deletion.

Protect an image or repository from deletion

Protect an image from deletion

To allow the myrepo:tag image to be updated but not deleted, run the following command:

az acr repository update \
    --name myregistry --image myrepo:tag \
    --delete-enabled false --write-enabled true

Protect a repository from deletion

The following command sets the myrepo repository so it can't be deleted. Individual images can still be updated or deleted.

az acr repository update \
    --name myregistry --repository myrepo \
    --delete-enabled false --write-enabled true

Prevent read operations on an image or repository

To prevent read (pull) operations on the myrepo:tag image, run the following command:

az acr repository update \
    --name myregistry --image myrepo:tag \
    --read-enabled false

To prevent read operations on all images in the myrepo repository, run the following command:

az acr repository update \
    --name myregistry --repository myrepo \
    --read-enabled false

Unlock an image or repository

To restore the default behavior of the myrepo:tag image so that it can be deleted and updated, run the following command:

az acr repository update \
    --name myregistry --image myrepo:tag \
    --delete-enabled true --write-enabled true

To restore the default behavior of the myrepo repository and all images so that they can be deleted and updated, run the following command:

az acr repository update \
    --name myregistry --repository myrepo \
    --delete-enabled true --write-enabled true

Next steps

In this article, you learned about using the az acr repository update command to prevent deletion or updating of image versions in a repository. To set additional attributes, see the az acr repository update command reference.

To see the attributes set for an image version or repository, use the az acr repository show command.

For details about delete operations, see Delete container images in Azure Container Registry.

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