Tentative usage with join²
21 August 2018
Zentralbibliothek, Forschungszentrum Jülich
Kubernetes is installed on a cluster of computers. One master, many nodes. You don’t ssh into the cluster but talk to the master though HTTPS.
Kubernetes – the project
- Started at Google 2014. Actively worked on by people of Google, Microsoft, RedHat.
- 857 current contributors.
- Half of Fortune 100 companies use it.
- Comparison of commits/month with Docker Swarm:
For big deployments:
- Optimal use of resources.
- Easy scaling.
- Comfortable container management.
- Full configuration as YAML files, most of them could live in the join² Git.
- Self-healing: Constant comparison of desired state and actual state.
1. Install “naked” Ubuntu/Debian/RedHat. Disable swap.
2. Prepare directories for persistent data.
3. Install Docker & Kubernetes through package manager.
4. Call “
kubeadm init” on master, “
kubeadm join …” on nodes.
5. Install “Weave Net” (one-liner).
6. Download the
kubectl binary to your workstation.
kubectl is the command line tool; your scripts may contact the HTTPS API directly.
- Kubernetes’ state is objects of different types, e.g. Deployment, CronJob, PersistentVolume, Secret, ConfigMap.
- One object, one YAML file. Typical size: 10–30 lines per object.
- All those YAML files are your wishlist.
- Typical workflow: You write YAML files and upload them with kubectl to the cluster. Then wait and see it being realised.
Some kubectl commands to get the idea:
kubectl create -f myapp.yaml
kubectl get deployments
kubectl logs myapp-1534841280-tj5mb
kubectl delete deployment myapp
Kubernetes & join²
- Highly tentative; there are no Kubernetes plans for join² yet.
- Jülich uses Kubernetes for their RDM projects, possibly also for JuSER.
- Existing images may stay as they are.
- Kubernetes and non-Kubernetes join² instances can coexist.
- 80% of YAML files would be the same for all instances. Different are: Some ConfigMaps, most Secrets, and all PersistentVolumes.
- Working on YAML files in the join² Git may streamline our configurations and improve collaboration and debugging.
- Vision: IT department offers managed Kubernetes. Then, we would't have to ssh anymore.
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