devops cheasheet

4 minute read

Docker Command
Bash shell to running docker docker exec -it 56a93cc76fde /bin/bash
Run nginx docker run --name nginx -p 80:80 nginx
   
Minikube  
   
Kubernetes  
Master stateless kubernetes mater is stateless so we can start 5 masters if we want. 3 masters per 5000 nodes maybe.
DaemonSet enforces a single pod on each node (with filtering)
Service implemented by iptables, creates A record in DNS pod in control plane of k8s.
KubeProxy process the brain behind service it’s updating the iptables. packets not going through it.
Ports Containers on same pod cannot have same port on different pods can have. On same port communicate via same loopback network interface.
Readiness/Liveness Readiness => false, removed from LB, Liveness => false, kubectl kills pod.
get labels for pod kubectl get pod --show-labels
services endpoints kubectl get endpoints
Expose as a service `kubectl expose
NodePort Exposes the service on each Node’s IP at a static port (the NodePort ). A ClusterIP service, to which the NodePort service will route, is automatically created. You’ll be able to contact the NodePort service, from outside the cluster, by requesting : .
Get host where node runs kubectl get pod -owide
Service Exposure ip/port ClusterIp exposure (k8s) < NodePort exposure (vms) < LoadBalancer exposure (world). kubectl expose deployment tomerbdhost --name my-svc --type [ClusterIp|NodePort|LoadBalancer] --port 3000 --target-port 3000
Expose LoadBalancer It knew to automatically go to GCP and expose it on google load balancer in google console search for Load Balancers in google cloud console and this will be your external ip you just need to run the above command it autoamtically connect to one of your load balancers.
kubectl apply Reupload kubernetes file yaml kubectl apply -f host-id-deployment.yaml
Scheduling  
Node affinity If you want to control that some pods are on same node so when the pods communicate they are affinity to same node. Or use labels to have pods on same zone or region
labels kubectl label set something, define labels and then assign pods to labels for nodes
node affinity like labels selector but more advanced best effort
Ingress Ingress is data (rules) ingress controller process that reads it that the outcome is nginx!
  kubectl create -f ingress.yaml
  You must define also IngressController which loads ingress rules to load balancer.
  We do SSL termination with the nginx and its config (ingress)
Namespaces In between namespaces add FQDN as prefix to DNS.
Clusters kubectl config get-clusters
  less ~/.kube/config
kubectl  
get pods kubectl get pod -o wide
print yaml kubectl get ingress -o yaml # print yaml for my ingress
  kubetl get <id> -o yaml
  kubectl edit ds # edit DatemonSet yamls
ls kubectl exec etcd-0 -- ls -ltr /var/run/etcd
watch kubectl get pods -w
delete pod kubectl delete pod <podname>
delete by file kubectl delete -f persistency/etcdCluster.yaml
labels kubectl get node —show-labels
Volumes  
Dynamic claims You can have dynamic claims so like in statefulSets volumes are created dynamically for them.
Networking  
docker bridge Docker host creats br0 bridge
docker veth every container has veth interface
kuberentes different pod can communicate with another on the cluster
NodePort export service port on VM
Pod networking CNI - Container Network Interface - —network-plugin=cni plugin for networking simulating hardware for kubernetes.
—network-plugin=kubenet docker networking, then we need to configure routing or our cloud provider gives us the ip, but cannot do overlay networks, in cloud we are given the networking
—network-plugin=cni with this we don’t use docker networking we use custom like flannel, in on premise very important to know to choose, like cni that does firewall or not? today in our cluster all pods can tlak to all pods, so we need to choose the cni. with cni we write custom configuration for networking.
Overlay network abstraction above multiple networks so it simulates a single network like layer 2 as if we ar eon same switch however we are on mutiple networks.
flannel is one of the cni, its like sitting on exit-entry of vm’s and knwos to translate internally to the pods and externally to other machines.
preserve source ip The only way to preserve client source ip is by using external traffic policy OnlyLocal load balancer will remove any vm without pods all traffic will go to local pod traffic always goes to local pod on node.
StatefulSets kind: StatefulSet, Pets (not cattle), loading with same ip, with permanent storage, same identity
  kubectl get statefulset
Security two entities, users (us), service-accounts - in cluster api access for services.
Item Command
   
run container docker run -p 3000:3000 tomerbd/tomerbdhost:1.0
gcloud gcloud container clusters get-credentials tomer-ben-david --zone europe-west1-b --project cldz-course-thomsonreuters
kubectl run kubectl run tomerbdhost --image tomerbd/tomerbdhost:1.0 --port=3000 # => run our image at google cloud
get pods shell acce kubectl get pod ; kubectl exec -it tomerbdhost-2796297851-s5xmw sh
Expose to NodePort kubectl expose deployment tomerbdhost --name tomerbdhost-svc --type NodePort --port 3000 --target-port 3000
Ingress kubectl create -f ingress.yaml

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