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Application configuration

Marking an application for being updateable

In order for Argo CD Image Updater to know which applications it should inspect for updating the workloads' container images, the corresponding Kubernetes resource needs to be correctly annotated. Argo CD Image Updater will inspect only resources of kind, that is, your Argo CD Application resources. Annotations on other kinds of resources will have no effect and will not be considered.

For its annotations, Argo CD Image Updater uses the following prefix:

As explained earlier, your Argo CD applications must be of either Kustomize or Helm type. Other types of applications will be ignored.

So, in order for Argo CD Image Updater to consider your application for the update of its images, at least the following criteria must be met:

  • Your Application resource is annotated with the mandatory annotation of, which contains at least one valid image specification (see Images Configuration).

  • Your Application resource is of type Helm or Kustomize

An example of a correctly annotated Application resources might look like:

kind: Application
  name: guestbook
  namespace: argocd
    namespace: guestbook
    server: https://kubernetes.default.svc
  project: default
    path: helm-guestbook
    targetRevision: HEAD

Configuring the write-back method

The Argo CD Image Updater supports two distinct methods on how to update images of an application:

  • imperative, via Argo CD API
  • declarative, by pushing changes to a Git repository

Depending on your setup and requirements, you can chose the write-back method per Application, but not per image. As a rule of thumb, if you are managing Application in Git (i.e. in an app-of-apps setup), you most likely want to chose the Git write-back method.

The write-back method is configured via an annotation on the Application resource: <method>

Where <method> must be one of argocd (imperative) or git (declarative).

The default used by Argo CD Image Updater is argocd.

Using the Argo CD API write-back method

When using the Argo CD API to write back changes, Argo CD Image Updater will perform a similar action as argocd app set --parameter ... to instruct Argo CD to re-render the manifests using those parameters.

This method is pseudo-persistent. If you delete the Application resource from the cluster and re-create it, changes made by Image Updater will be gone. The same is true if you manage your Application resources using Git, and the version stored in Git is synced over the resource in the cluster. This method is most suitable for Applications also created imperatively, i.e. using the Web UI or CLI.

This method is the default and requires no further configuration.

Using the Git write-back method

Compatibility with Argo CD

The Git write-back method requires a feature in Argo CD that has been introduced with Argo CD v2.0. Git write-back will not work with earlier versions of Argo CD.

The git write-back method uses Git to permanently store its parameter overrides along with the Application's resource manifests. This will enable persistent storage of the parameters in Git.

By default, Argo CD Image Updater will store the parameter in a file named .argocd-source-<appName>.yaml in the path used by the Application to source its manifests from. This will allow Argo CD to pick up parameters in this file, when rendering manifests for the Application named <appName>. Using this approach will also minimize the possibility of merge conflicts, as long as no other party in your CI will modify this file.

A note on the application's target revision

Due to the nature of how Git write-back works, your application really should track a branch instead of a revision. If you track HEAD, a tag or a certain revision with your application, you must override the branch in an annotation (see below). But in order for Argo CD to pick up the change after Image Updater has committed & pushed the change, you really want to set it up so it tracks a branch.

To use the Git write-back method, annotate your Application with the right write-back method: git

In order to better decide whether this method is suitable for your use-case, this is the workflow how Argo CD Image Updater performs change to Git:

  • Fetch the remote repository from location specified by .spec.source.repoURL in the Argo CD Application manifest, using credentials specified as annotation (see below)
  • Check-out the target branch on the local copy. The target branch is either taken from an annotation (see below), or if no annotation is set, taken from .spec.source.targetRevision in the Application manifest
  • Create or update .argocd-source-<appName>.yaml in the local repository
  • Commit the changed file to the local repository
  • Push the commit to the remote repository, using credentials specified as annotation (see below)

The important pieces to this workflow are:

  • Credentials configured in Argo CD will not be re-used, you have to supply a dedicated set of credentials

  • Write-back is a commit to the tracking branch of the Application. Currently, Image Updater does not support creating a new branch or creating pull or merge requests

  • If .spec.source.targetRevision does not reference a branch, you will have to specify the branch to use manually (see below)

General configuration

Configuration for the Git write-back method comes from two sources:

  • The Argo CD Application manifest is used to define the repository and the path where the .argocd-source-<appName>.yaml should be written to. These are defined in .spec.source.repoURL and .spec.source.path fields, respectively. Additionally, .spec.source.targetRevision is used to define the branch to commit and push the changes to. The branch to use can be overridden by an annotation, see below.

  • A set of annotations on the Application manifest, see below

Specifying Git credentials

By default Argo CD Image Updater re-uses the credentials you have configured in Argo CD for accessing the repository.

If you don't want to use credentials configured for Argo CD you can use other credentials stored in a Kubernetes secret, which needs to be accessible by the Argo CD Image Updater's Service Account. The secret should be specified in annotation using git:<credref> format. Where <credref> might take one of following values:

  • repocreds (default) - Git repository credentials configured in Argo CD settings
  • secret:<namespace>/<secret> - namespace and secret name.

Example: git:secret:argocd-image-updater/git-creds

If the repository is accessed using HTTPS, the secret must contain two fields: username which holds the Git username, and password which holds the user's password or a private access token (PAT) with write access to the repository. You can generate such a secret using kubectl, e.g.:

kubectl -n argocd-image-updater secret create generic git-creds \
  --from-literal=username=someuser \

If the repository is accessed using SSH, the secret must contain the field sshPrivateKey, which holds a SSH private key in OpenSSH-compatible PEM format. To create such a secret from an existing private key, you can use kubectl, for example:

kubectl -n argocd-image-updater secret create generic git-creds \

Specifying a branch to commit to

By default, Argo CD Image Updater will use the value found in the Application spec at .spec.source.targetRevision as Git branch to checkout, commit to and push back the changes it made. In some scenarios, this might not be what is desired, and you can (and maybe have to) override the branch to use by specifying the annotation on the Application manifest.

The value of this annotation will define the Git branch to use, for example the following would use GitHub's default main branch: main

Specifying the user and email address for commits

Each Git commit is associated with an author's name and email address. If not configured, commits performed by Argo CD Image Updater will use argocd-image-updater <> as the author. You can override the author using the --git-commit-user and --git-commit-email command line switches or set git.user and in the argocd-image-updater-config ConfigMap.