flux2/docs/guides/image-update.md

Automate image updates to Git

This guide walks you through configuring container image scanning and deployment rollouts with Flux.

For a container image you can configure Flux to:

• scan the container registry and fetch the image tags
• select the latest tag based on a semver range
• replace the tag in Kubernetes manifests (YAML format)
• checkout a branch, commit and push the changes to the remote Git repository
• apply the changes in-cluster and rollout the container image

!!! warning "Alpha version" Note that the image update feature is currently alpha and, it only supports semver filters. In the future we plan to add support for other filtering options. Please see the roadmap for more details.

For production environments, this feature allows you to automatically deploy application patches (CVEs and bug fixes), and keep a record of all deployments in Git history.

For staging environments, this features allow you to deploy the latest prerelease of an application, without having to manually edit its deployment manifests in Git.

Production CI/CD workflow:

• DEV: push a bug fix to the app repository
• DEV: bump the patch version and release e.g. v1.0.1
• CI: build and push a container image tagged as registry.domain/org/app:v1.0.1
• CD: pull the latest image metadata from the app registry (Flux image scanning)
• CD: update the image tag in the app manifest to v1.0.1 (Flux cluster to Git reconciliation)
• CD: deploy v1.0.1 to production clusters (Flux Git to cluster reconciliation)

Prerequisites

You will need a Kubernetes cluster version 1.16 or newer and kubectl version 1.18. For a quick local test, you can use Kubernetes kind. Any other Kubernetes setup will work as well.

In order to follow the guide you'll need a GitHub account and a personal access token that can create repositories (check all permissions under repo).

Export your GitHub personal access token and username:

export GITHUB_TOKEN=<your-token>
export GITHUB_USER=<your-username>

Install Flux

Install Flux with the image automation components:

flux bootstrap github \
  --components-extra=image-reflector-controller,image-automation-controller \
  --owner=$GITHUB_USER \
  --repository=flux-image-updates \
  --branch=main \
  --path=clusters/my-cluster \
  --token-auth \
  --personal

The bootstrap command creates a repository if one doesn't exist, and commits the manifests for the Flux components to the default branch at the specified path. It then configures the target cluster to synchronize with the specified path inside the repository.

!!! hint "GitLab and other Git platforms" You can install Flux and bootstrap repositories hosted on GitLab, BitBucket, Azure DevOps and any other Git provider that support SSH or token-based authentication. When using SSH, make sure the deploy key is configured with write access. Please see the installation guide for more details.

Deploy a demo app

We'll be using a tiny webapp called podinfo to showcase the image update feature.

Clone your repository with:

git clone https://github.com/$GITHUB_USER/flux-image-updates
cd flux-image-updates

Add the podinfo Kubernetes deployment file inside cluster/my-cluster:

curl -sL https://raw.githubusercontent.com/stefanprodan/podinfo/5.0.0/kustomize/deployment.yaml \
> ./clusters/my-cluster/podinfo-deployment.yaml

Commit and push changes to main branch:

git add -A && \
git commit -m "add podinfo deployment" && \
git push origin main

Tell Flux to pull and apply the changes or wait one minute for Flux to detect the changes on its own:

flux reconcile kustomization flux-system --with-source

Print the podinfo image deployed on your cluster:

$ kubectl get deployment/podinfo -oyaml | grep 'image:'
image: ghcr.io/stefanprodan/podinfo:5.0.0

Configure image scanning

Create an ImageRepository to tell Flux which container registry to scan for new tags:

flux create image repository podinfo \
--image=ghcr.io/stefanprodan/podinfo \
--interval=1m \
--export > ./clusters/my-cluster/podinfo-registry.yaml

The above command generates the following manifest:

apiVersion: image.toolkit.fluxcd.io/v1alpha1
kind: ImageRepository
metadata:
  name: podinfo
  namespace: flux-system
spec:
  image: ghcr.io/stefanprodan/podinfo
  interval: 1m0s

For private images, you can create a Kubernetes secret in the same namespace as the ImageRepository with kubectl create secret docker-registry. Then you can configure Flux to use the credentials by referencing the Kubernetes secret in the ImageRepository:

kind: ImageRepository
spec:
  secretRef:
    name: regcred

!!! hint "Storing secrets in Git" Note that if you want to store the image pull secret in Git, you can encrypt the manifest with Mozilla SOPS or Sealed Secrets.

Create an ImagePolicy to tell Flux which semver range to use when filtering tags:

flux create image policy podinfo \
--image-ref=podinfo \
--interval=1m \
--semver=5.0.x \
--export > ./clusters/my-cluster/podinfo-policy.yaml

The above command generates the following manifest:

apiVersion: image.toolkit.fluxcd.io/v1alpha1
kind: ImagePolicy
metadata:
  name: podinfo
  namespace: flux-system
spec:
  imageRepositoryRef:
    name: podinfo
  policy:
    semver:
      range: 5.0.x

!!! hint "semver ranges" A semver range that includes stable releases can be defined with 1.0.x (patch versions only) or >=1.0.0 <2.0.0 (minor and patch versions). If you want to include pre-release e.g. 1.0.0-rc.1, you can define a range like: ^1.x-0 or >1.0.0-rc <2.0.0-rc.

Commit and push changes to main branch:

git add -A && \
git commit -m "add podinfo image scan" && \
git push origin main

Tell Flux to pull and apply changes:

flux reconcile kustomization flux-system --with-source

Wait for Flux to fetch the image tag list from GitHub container registry:

$ flux get image repository podinfo
NAME   	READY	MESSAGE                       	LAST SCAN
podinfo	True 	successful scan, found 13 tags	2020-12-13T17:51:48+02:00

Find which image tag matches the policy semver range with:

$ flux get image policy podinfo
NAME   	READY	MESSAGE                   
podinfo	True 	Latest image tag for 'ghcr.io/stefanprodan/podinfo' resolved to: 5.0.3

Configure image updates

Edit the podinfo-deploy.yaml and add a maker to tell Flux which policy to use when updating the container image:

spec:
  containers:
  - name: podinfod
    image: ghcr.io/stefanprodan/podinfo:5.0.0 # {"$imagepolicy": "flux-system:podinfo"}

Create an ImageUpdateAutomation to tell Flux which Git repository to write image updates to:

flux create image update flux-system \
--git-repo-ref=flux-system \
--branch=main \
--author-name=fluxcdbot \
--author-email=fluxcdbot@users.noreply.github.com \
--commit-template="[ci skip] update image" \
--export > ./clusters/my-cluster/flux-system-automation.yaml

The above command generates the following manifest:

apiVersion: image.toolkit.fluxcd.io/v1alpha1
kind: ImageUpdateAutomation
metadata:
  name: flux-system
  namespace: flux-system
spec:
  checkout:
    branch: main
    gitRepositoryRef:
      name: flux-system
  commit:
    authorEmail: fluxcdbot@users.noreply.github.com
    authorName: fluxcdbot
    messageTemplate: '[ci skip] update image'
  interval: 1m0s
  update:
    setters: {}

Commit and push changes to main branch:

git add -A && \
git commit -m "add image updates automation" && \
git push origin main

Note that the ImageUpdateAutomation runs all the policies found in its namespace at the specified interval.

Tell Flux to pull and apply changes:

flux reconcile kustomization flux-system --with-source

In a couple of seconds Flux will push a commit to your repository with the latest image tag that matches the podinfo policy:

$ git pull && cat clusters/my-cluster/podinfo-deployment.yaml | grep "image:"
image: ghcr.io/stefanprodan/podinfo:5.0.3 # {"$imagepolicy": "flux-system:podinfo"}

Wait for Flux to apply the latest commit on the cluster and verify that podinfo was updated to 5.0.3:

$ watch "kubectl get deployment/podinfo -oyaml | grep 'image:'"
image: ghcr.io/stefanprodan/podinfo:5.0.3

Configure image update for custom resources

Besides Kubernetes native kinds (Deployment, StatefulSet, DaemonSet, CronJob), Flux can be used to patch image tags in any Kubernetes custom resource stored in Git.

The image policy marker format is:

• {"$imagepolicy": "<policy-namespace>:<policy-name>"}
• {"$imagepolicy": "<policy-namespace>:<policy-name>:tag"}

HelmRelease example:

apiVersion: helm.toolkit.fluxcd.io/v2beta1
kind: HelmRelease
metadata:
  name: podinfo
  namespace: default
spec:
  values:
    image:
      repository: ghcr.io/stefanprodan/podinfo
      tag: 5.0.0  # {"$imagepolicy": "flux-system:podinfo:tag"}

Tekton Task example:

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: golang
  namespace: default
spec:
  steps:
    - name: golang
      image: docker.io/golang:1.15.6 # {"$imagepolicy": "flux-system:golang"}

Flux Kustomization example:

apiVersion: kustomize.toolkit.fluxcd.io/v1beta1
kind: Kustomization
metadata:
  name: podinfo
  namespace: default
spec:
  images:
    - name: ghcr.io/stefanprodan/podinfo
      newName: ghcr.io/stefanprodan/podinfo
      newTag: 5.0.0 # {"$imagepolicy": "flux-system:podinfo:tag"}

Kustomize config (kustomization.yaml) example:

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- deployment.yaml
images:
- name: ghcr.io/stefanprodan/podinfo
  newName: ghcr.io/stefanprodan/podinfo
  newTag: 5.0.0 # {"$imagepolicy": "flux-system:podinfo:tag"}

ImageRepository cloud providers authentication

If relying on a cloud provider image repository, you might need to do some extra work in order to configure the ImageRepository resource credentials. Here are some common examples for the most popular cloud provider docker registries.

!!! warning "Workarounds" The examples below are intended as workaround solutions until native authentication mechanisms are implemented in Flux itself to support this in a more straightforward manner.

AWS Elastic Container Registry

The registry authentication credentials for ECR expire every 12 hours. Considering this limitation, one needs to ensure the credentials are being refreshed before expiration so that the controller can rely on them for authentication.

The solution proposed is to create a cronjob that runs every 6 hours which would re-create the docker-registry secret using a new token.

Edit and save the following snippet to a file ./clusters/my-cluster/ecr-sync.yaml, commit and push it to git.

kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: ecr-credentials-sync
  namespace: flux-system
rules:
- apiGroups: [""]
  resources:
  - secrets
  verbs:
  - delete
  - create
---
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: ecr-credentials-sync
  namespace: flux-system
subjects:
- kind: ServiceAccount
  name: ecr-credentials-sync
roleRef:
  kind: Role
  name: ecr-credentials-sync
  apiGroup: ""
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: ecr-credentials-sync
  # Uncomment and edit if using IRSA
  # annotations:
  #   eks.amazonaws.com/role-arn: <role arn>
---
apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: ecr-credentials-sync
  namespace: flux-system
spec:
  suspend: false
  schedule: 0 */6 * * *
  failedJobsHistoryLimit: 1
  successfulJobsHistoryLimit: 1
  jobTemplate:
    spec:
      template:
        spec:
          serviceAccountName: ecr-credentials-sync
          restartPolicy: Never
          volumes:
          - name: token
            emptyDir:
              medium: Memory
          initContainers:
          - image: amazon/aws-cli
            name: get-token
            imagePullPolicy: IfNotPresent
            # You will need to set the AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY environment variables if not using
            # IRSA. It is recommended to store the values in a Secret and load them in the container using envFrom.
            # envFrom:
            # - secretRef:
            #     name: aws-credentials
            env:
            - name: REGION
              value: us-east-1 # change this if ECR repo is in a different region
            volumeMounts:
            - mountPath: /token
              name: token
            command:
            - /bin/sh
            - -ce
            - aws ecr get-login-password --region ${REGION} > /token/ecr-token
          containers:
          - image: bitnami/kubectl
            name: create-secret
            imagePullPolicy: IfNotPresent
            env:
            - name: SECRET_NAME
              value: <secret name> # this is the generated Secret name
            - name:
              value: <account id>.dkr.ecr.<region>.amazonaws.com # fill in the account id and region
            volumeMounts:
            - mountPath: /token
              name: token
            command:
            - /bin/bash
            - -ce
            - |-
              kubectl delete secret --ignore-not-found $SECRET_NAME
              kubectl create secret docker-registry $SECRET_NAME \
                --docker-server="$ECR_REGISTRY" \
                --docker-username=AWS \
                --docker-password="$(</token/ecr-token)"              

!!! hint "Using IAM Roles for Service Accounts (IRSA)" If using IRSA, make sure the role attached to the service account has readonly access to ECR. The AWS managed policy arn:aws:iam::aws:policy/AmazonEC2ContainerRegistryReadOnly can be attached to the role.

Since the cronjob will not create a job right away, after applying the manifest, you can manually create an init job using the following command:

$ kubectl create job --from=cronjob/ecr-credentials-sync -n flux-system ecr-credentials-sync-init

GCP Container Registry

Using access token [short-lived]

!!!note "Workload Identity" Please ensure that you enable workload identity for your cluster, create a GCP service account that has access to the container registry and create an IAM policy binding between the GCP service account and the Kubernetes service account so that the pods created by the cronjob can access GCP APIs and get the token. Take a look at this guide

The access token for GCR expires hourly. Considering this limitation, one needs to ensure the credentials are being refreshed before expiration so that the controller can rely on them for authentication.

The solution proposed is to create a cronjob that runs every 45 minutes which would re-create the docker-registry secret using a new token.

Edit and save the following snippet to a file ./clusters/my-cluster/gcr-sync.yaml, commit and push it to git.

kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: gcr-credentials-sync
  namespace: flux-system
rules:
- apiGroups: [""]
  resources:
  - secrets
  verbs:
  - delete
  - create
---
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: gcr-credentials-sync
  namespace: flux-system
subjects:
- kind: ServiceAccount
  name: gcr-credentials-sync
roleRef:
  kind: Role
  name: gcr-credentials-sync
  apiGroup: ""
---
apiVersion: v1
kind: ServiceAccount
metadata:
  annotations:
    iam.gke.io/gcp-service-account: <name-of-service-account>@<project-id>.iam.gserviceaccount.com
  name: gcr-credentials-sync
  namespace: flux-system
---
apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: gcr-credentials-sync
  namespace: flux-system
spec:
  suspend: false
  schedule: "*/45 * * * *"
  failedJobsHistoryLimit: 1
  successfulJobsHistoryLimit: 1
  jobTemplate:
    spec:
      template:
        spec:
          serviceAccountName: gcr-credentials-sync
          restartPolicy: Never
          containers:
          - image: google/cloud-sdk
            name: create-secret
            imagePullPolicy: IfNotPresent
            env:
            - name: SECRET_NAME
              value: <SECRET_NAME> # this is the generated Secret name
            - name: GCR_REGISTRY
              value: <REGISTRY_NAME> # fill in the registry name e.g gcr.io, eu.gcr.io
            command:
            - /bin/bash
            - -ce
            - |-
              kubectl delete secret --ignore-not-found $SECRET_NAME
              kubectl create secret docker-registry $SECRET_NAME \
                --docker-server="$GCR_REGISTRY" \
                --docker-username=oauth2accesstoken \
                --docker-password="$(gcloud auth print-access-token)"               

Since the cronjob will not create a job right away, after applying the manifest, you can manually create an init job using the following command:

$ kubectl create job --from=cronjob/gcr-credentials-sync -n flux-system gcr-credentials-sync-init

Using a JSON key [long-lived]

!!! warning "Less secure option" From Google documentation on authenticating container registry > A user-managed key-pair that you can use as a credential for a service account. Because the credential is long-lived, it is the least secure option of all the available authentication methods. When possible, use an access token or another available authentication method to reduce the risk of unauthorized access to your artifacts. If you must use a service account key, ensure that you follow best practices for managing credentials.

Json keys doesn't expire so we don't need a cronjob, we just need to create the secret and reference it in the ImagePolicy.

First, create a json key file by following this documentation. Grant the service account the role of Container Registry Service Agent so that it can access GCR and download the json file.

Then create a secret, encrypt it using Mozilla SOPS or Sealed Secrets , commit and push the encypted file to git.

 kubectl create secret docker-registry <secret-name> \
                --docker-server=<GCR-REGISTRY> \ # e.g gcr.io
                --docker-username=_json_key \
                --docker-password="$(cat <downloaded-json-file>)" 

Azure Container Registry

TODO