| Name | Description |
|---|---|
| kube-apiserver | validates and configures data for the api objects which include pods, services, replicationcontrollers, and others |
| etcd | distributed k/v store |
| kube-scheduler | schedule pods to run on selected nodes |
| kube-controller-manager | daemon that embeds the core control loops shipped with kubernetes |
Components and Services running on Worker Nodes:
| Name | Description |
|---|---|
| kubelet | node-agent that runs on each node |
| kube-proxy connection | forwarding |
| container runtime | container runtimes supported by kubernets: (docker, rkt, runc, etc) |
Show nodes in the cluster:
kubectl get nodes
Show nodes with extra info:
kubectl get nodes -o wide
Show nodes in yaml format:
kubectl get nodes -o yaml
Describe nodes:
kubectl describe nodes
Show nodes in yaml format
kubectl get nodes -o yaml
Show node labels
kubectl get node --show-labels
Show nodes with specific label
kubectl get node --selector=[label_name]
Show value from a key
kubectl get nodes -o jsonpath='{.items[*].status.addresses[?(@.type=="External IP")].address}'
Get node resource information
kubectl top node [node_name]
- The single smallest interactable unit in Kubernetes.
- a Pod can be comprimised of multiple containers that will form a unit deployed on a single node together
- a Pod receives one IP which is shared between containers
Show pods:
kubectl get pods
Show pods from all namespaces:
kubectl get pods --all-namespaces
Show pods in yaml format:
kubectl get pods --output yaml
Show system pods
kubectl get pods --namespace kube-system
Show pods in yaml format
kubectl get pods --output yaml
Dont truncate output
kubectl get pods -o wide
Show pod info
kubectl get pod svclb-traefik --namespace kube-system
Show pod info from app selector
kubectl get pods --selector app=svclb-traefik --namespace kube-system
Show all pods info from all ns
kubectl describe pods --all-namespaces
Show pods with labels
kubectl get pods --show-labels
Dump pod info in yaml
kubectl get pod svclb-traefik --namespace kube-system -o yaml --export
Export pod info to file
kubectl get pod svclb-traefik --namespace kube-system -o yaml --export > exported.yml
Show pods, sort by node
kubectl get pods -o wide --sort-by="{.spec.nodeName}"
Show pods, sort by restarts
kubectl get pods --sort-by="{.status.containerStatuses[:1].restartCount}"
Show pods on a node
kubectl get pods --all-namespaces -o wide --field-selector spec.nodeName="ip-10-10-4-20.eu-west-1.compute.internal"
Show pods from a deployment
kubectl get pods --output wide --selector app.kubernetes.io/name=my-app
Run a pod without a deployment (Restart policy with Never wont create a deployment)
kubectl run pod1 --image=alpine --restart=Never -- ping localhost
Run a pod without a deployment (Using generator flag)
kubectl run pod2 --generator=run-pod/v1 --image=alpine -- ping localhost
Run a debug pod:
kubectl run --generator=run-pod/v1 -it --rm load-generator --image=busybox /bin/sh
List deployments
kubectl get deployment
List deployments from all namespaces
kubectl get deployments --all-namespaces
Show deployment info
kubectl get deployment/myapp -o yaml
Run a Nginx Deployment with 2 Replicas
kubectl run nginx01 --image=nginx --replicas=2 --port=80
Tail logs from a pod:
kubectl logs -f drone-agent-557ddc7bb4-crjns
Tail logs from a container (when two or more containers runs in a pod):
kubectl logs -f drone-agent-557ddc7bb4-crjns -c docker-in-docker
Show pods and dont truncate the output:
kubectl get pods -o wide
Show pods with their labels:
kubectl get pods --show-labels
Show pods from a specific deployment:
kubectl get pods --output wide --selector app.kubernetes.io/name=my-test-app
Show pods on specific node:
kubectl get pods -o wide --field-selector spec.nodeName="ip-10-0-1-20.eu-west-1.compute.internal"
Show pods, sort output by node:
kubectl get pods -o wide --sort-by="{.spec.nodeName}"
Show pods, sort output by restarts:
kubectl get pods --sort-by="{.status.containerStatuses[:1].restartCount}"
Let's look at a pod:
$ kubectl get pods -o wide
pistack-blog-7cddc5b979-grbv4 0/1 ContainerCreating 0 4m47s <none> rpi-03 <none> <none>
We can see it's been in a ContainerCreating state for some time, we can have a look at the logs:
$ kubectl logs -f pod/pistack-blog-7cddc5b979-grbv4
Error from server (BadRequest): container "ghost" in pod "pistack-blog-7cddc5b979-grbv4" is waiting to start: ContainerCreating
Let's describe the pod to see whats currently happening:
$ kubectl describe pod/pistack-blog-7cddc5b979-grbv4
Name: pistack-blog-7cddc5b979-grbv4
Namespace: default
...
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 8m21s default-scheduler Successfully assigned default/pistack-blog-7cddc5b979-grbv4 to rpi-03
Normal Pulling 8m20s kubelet Pulling image "alexellis2/ghost-on-docker:armv6"
We can see that the it's currently pulling the image from the registry, let's try again after a minute or so:
$ kubectl describe pod/pistack-blog-7cddc5b979-grbv4
Name: pistack-blog-7cddc5b979-grbv4
Namespace: default
...
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 8m21s default-scheduler Successfully assigned default/pistack-blog-7cddc5b979-grbv4 to rpi-03
Normal Pulling 8m20s kubelet Pulling image "alexellis2/ghost-on-docker:armv6"
Normal Pulled 10s kubelet Successfully pulled image "alexellis2/ghost-on-docker:armv6"
Normal Created 6s kubelet Created container ghost
Normal Started 4s kubelet Started container ghost
We can also look at our nodes utilization, should we thought it was resource related:
$ kubectl top nodes
NAME CPU(cores) CPU% MEMORY(bytes) MEMORY%
rpi-01 163m 4% 303Mi 32%
rpi-02 229m 5% 318Mi 34%
rpi-03 276m 6% 330Mi 35%
rpi-05 1107m 27% 2222Mi 57%
rpi-06 298m 7% 467Mi 12%
rpi-07 238m 5% 416Mi 10%
Kubectl Output Formatting:
Kubernetes Cheatsheet:
CI/CD with Kubernets: