Kubernetes and GitOps with Flux CD V2.0

GitOps could be the next big thing in cloud automation so I’d give it a try with my in house hybrid Kubernetes cluster. I was recommended to try Flux CD and there’s a good reference project initiated by my colleage: k8s-gitops.

However, in order to fully understand how to use Flux CD, I chose to start from scratch. Following the official instructions it didn’t take me long to fully enable GitOps on my cluster. Here’s how I did it on my laptop running Ubuntu:

First, create a GitHub PAT(Personal Access Token) with full repository permissions. Details can be read here. Also make sure you can create a private repository in GitHub (everyone gets 1 for free). Export GitHub username and PAT as environment variables as following:

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

Latest Flux2 CLI can be downloaded here. You can also use the installation script from Flux if you fully trust it:

curl -s https://toolkit.fluxcd.io/install.sh | sudo bash

From this step onward, you will need access to a Kubernetes cluster, eg. kubectl cluster-info command works and returns cluster information. Check Flux2’s prerequisites with:

flux check --pre
► checking prerequisites
✔ kubectl 1.18.6 >=1.18.0
✔ Kubernetes 1.18.9 >=1.16.0
✔ prerequisites checks passed

Then the Flux2 command below can be executed to bootstrap a private GitHub repository flux-gitops using your GitHub PAT and the repository will be your cluster-as-code command center for GitOps practice, also the CRD(Custom Resource Definition) and controllers for Flux2 will be installed to the current cluster

flux bootstrap github \
  --owner=$GITHUB_USER \
  --repository=flux-gitops \
  --branch=main \
  --path=home-cluster \
  --personal

In the generated flux-gitops repository, the file structure looks like

flux-gitops
  - home-cluster
    - flux-system

Now you can simply add Helm charts or Kustomization templates into this repository and the changes will be applied to the cluster automatically. The following commands will create a simple namespace in the cluster, then register it with Flux2. After the changes pushed to GitHub, Flux2 controllers will apply the changes and create the new namespace.

cd flux-gitops/home-cluster
mkdir my-test
cd my-test
kustomize create
kubectl create namespace my-test --dry-run=client -o yaml > ns.yaml
kustomize edit add resource ns.yaml
cd .. # in home-cluster
# this step is redundant as any directory with a kustomization.yaml file in it will be automatically applied.
flux create kustomization my-test --source=flux-system --path=home-cluster/my-test --prune=true --validation=client --interval=2m --export > my-test.yaml
# check-in everything to test GitOps
# only add my-test directory if the above step is skipped
git add my-test my-test.yaml
git commit -m "Added my-test"
git push

Then you use a watch command to see how the new change get applied

watch flux get kustomizations
NAME                    READY   MESSAGE                                                         REVISION                                        SUSPENDED
flux-system             True    Applied revision: main/529288eed6105909a97f0d3539bc68e5e934418a main/529288eed6105909a97f0d3539bc68e5e934418a   False
my-test                 True    Applied revision: main/529288eed6105909a97f0d3539bc68e5e934418a main/529288eed6105909a97f0d3539bc68e5e934418a   False

That’s it, the Flux2 Hello-world. 🙂

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