Container Orchaestration
Container/pod operations: Docker vs Kubernetes vs Rancher
- Kubernetes largerly use kubectl, kubeadm.
- Docker also have Swarm and Enterprise Edition that does Orchaestration
- Rancher 1.0 use its own system, 2.x can use kubernetes.
- Singularity is not included at this time as it does not have build-in orchaestration.
Docker/EE k8s Rancher
==================== ====================== ===================
version kubectl version
env info docker info kubectl cluster-info rancher environment
Get image from registry docker pull
List images docker images -a
Remove images docker rmi IMG
Build image docker image build
Push img to registry docker image push
Start a container/pod docker run kubectl run rancher stack create
Restart/Upgrade a pod docker start kubectl apply -f yml rancher up
List running pods docker ps kubectl get pods rancher ps
Stop container docker stop
Clear container docker rm NAME kubectl delete deployments --all (?)
Get container's logs docker logs kubectl logs rancher logs
Shell into container docker exec -it kubectl exec -it rancher exec -it # all docker stuff, -it for interactive terminal
Kubernetes
minikube start # single node for very simple dev, http://localhost:8080
kubectl version
kubectl cluster-info
kubectl cluster-info dump
source <(kubectl completion bash) # enable bash autocompletion #># maybe add to .bashrc
kubectl run hello-minikube --image=k8s.gcr.io/echoserver:1.4 --port=8080
kubectl expose deployment hello-minikube --type=NodePort
kubectl get pod
curl $(minikube service hello-minikube --url)
# see docker process/container that is running inside the pod (eg VirtualBox)
eval $(minikube docker-env)
docker ps
minikube dashboard # will launch a browser to eg
http://192.168.99.100:30000/#!/overview?namespace=default
minikube ip
minikube service list
minikube stop
kubeadm
kubeadm cluster
2021.09
instructions from Kubernetes.io instruction on installing a cluster:
Official setup
doc
Kubectl
-------
This is command line tool to interact with cluster.
Should be easy to install, for Linux, etc.
https://kubernetes.io/docs/tasks/tools/install-kubectl-linux/
Kubelet
-------
This is the daemon process that run on the worker nodes.
Think slurmd on compute notes here.
Inbound ports:
- 10250 kubelet API
- 30000-32767 NodePort Servicesâ€
There are version requirements:
- Kubelet can NOT be newer than KubeAdm.
- Kubelet can be 1 minor release behind KubeAdm.
Kubeadm
-------
Control workers, create cluster. the real orchestrator.
Can get RHEL, Debian binaries. Google host a yum repo for rpm.
Non-package manager binaries available via github.
Etcd... API server...
Network
-------
additional vlan creation manageable via kubeadm would be nice for growth.
But for a small/static deployment, switch control by kubeAdm not needed.
A private network still need to be setup and used by kubernetes.
Container runtimes
Docker used to be the standard. But in 2020.12, the "dockershim" is being deprecated by kubernetes.
Kubernetes 1.20 still supports it, with a warning.
Kubernetes 1.22 (released 2021-08) maybe last version supporting dockershim.
Kubernetes 1.23? will only support CRI at that point? Will docker support CRI by this point?
Another company will provide a dockershim-ed version of kubernetes, at support expense?
CRI-O maybe the new container substrate Google is pushing for.
podman does not work with Kubernetes, so RHEL 8 maybe an issue.
Should be able to install Docker via non OS provided rpm.
containerd, supported. Developed by Docker, use OCI image format, and supports CRI.
Docker currently comes with this (in addition to docker), and it is the only "dual container" env that Kubeadm will support without erroring out during install.
Singularity not mentioned in Kubernetes.io site.
Sylabs doc
says it support is via CRI standard interface. See
See Diff b/w Docker, containerD, CRI-O and runc at Tutorial Works on the many nuance of the container stack.
Ref
2020:
- What is Kubernetes? concise intro by RH
- Kubernetes clustering choices
Kubeadm (Baremetal on CentOS)
Fedora multi-node
- Create Custom Kubernetes Cluster from Scratch
- Kubespray: Kubernetes On-prem and cloud (as opposed to Kops or Kubeadm)
- Large (100+) deploymnents of K8s recommendations.
- Kubernetes on DC/OS (Medosphere)
-
-
Rancher
- Rancher is open source, Free to run, Premium for support service.
A Guide to Kubernetes with Rancher (sale brochure from 2021) page 11 states: Commitment-Free Open Source. No different binary for Free vs Enterprise. Just pay for support. (install over existing kubernetes cluster, so just provide GUI, view, management, but not an actual kubernetes cluster?
- RanchOS is a lightweight OS for hosting containers.
- Install trivially as a docker container.
# create an app stack (list of containers) to be run together
# StackName is a directory containing docker compose yaml definition file listing all necessary containers
rancher stack create StackName
# redeploy a running application as per new spec (eg version upgrade)
rancher up --force-upgrade -d --stack StackName
# confirm upgrade (why was this needed?)
rancher up --confirm-upgrade -d --stack StackName
# look at logs of serverice. web is the name of a service in the demo stack
rancher logs StackName/web
# scale the service "web" to have 2 instances:
rancher scale StackName/web=2
# get shell into container (will ask when when there are 1+ instance)
# largely same as docker exec
rancher exec -it StackName/web /bin/bash
Container Landscape
cncf.io lanscape chat circa 2018.
(They have "interactive" view online, but that's mostly a dynamic list of links, don't give big picture view).
hoti1
bofh1
