Kubernetes cheat sheet

check all k8s actions

kubectl get events

restart kubelet

sudo systemctl restart kubelet

uncordon a node:

politeles@cp:~$ kubectl get node NAME STATUS ROLES AGE VERSION cp Ready,SchedulingDisabled control-plane 33h v1.25.1 worker1 Ready 32h v1.24.1 politeles@cp:~$ kubectl uncordon cp node/cp uncordoned politeles@cp:~$ kubectl get node NAME STATUS ROLES AGE VERSION cp Ready control-plane 33h v1.25.1 worker1 Ready 32h v1.24.1

replace a deployment

kubectl replace -f first.yaml

In which node is executing a pod

politeles@cp:~$ kubectl describe pod nginx-6c8b449b8f-87d4t | grep Node:
Node:         worker1/10.0.2.5

deploy with a load balancer

kubectl expose deployment nginx –type=LoadBalancer

ETCD Maintenance

Log into container

kubectl -n kube-system exec -it etcd-cp -- sh

Get the certificates:

cd /etc/kubernetes/pki/etcd
sh-5.1# echo *
ca.crt ca.key healthcheck-client.crt healthcheck-client.key peer.crt peer.key server.crt server.key

backup data dir

politeles@cp:~$ sudo grep data-dir /etc/kubernetes/manifests/etcd.yaml
[sudo] password for politeles:
    - --data-dir=/var/lib/etcd

Health check:

 kubectl -n kube-system exec -it etcd-cp -- sh \
> -c "ETCDCTL_API=3 \
> ETCDCTL_CACERT=/etc/kubernetes/pki/etcd/ca.crt \
> ETCDCTL_CERT=/etc/kubernetes/pki/etcd/server.crt \
> ETCDCTL_KEY=/etc/kubernetes/pki/etcd/server.key \
> etcdctl endpoint health"

kubectl -n kube-system exec -it etcd-cp – sh
> -c “ETCDCTL_API=3
> ETCDCTL_CACERT=/etc/kubernetes/pki/etcd/ca.crt
> ETCDCTL_CERT=/etc/kubernetes/pki/etcd/server.crt
> ETCDCTL_KEY=/etc/kubernetes/pki/etcd/server.key
> etcdctl –endpoints=https://127.0.0.1:2379 member list”

Save snapshot of etcd:

politeles@cp:~$ kubectl -n kube-system exec -it etcd-cp -- sh -c "ETCDCTL_API=3 \
ETCDCTL_CACERT=/etc/kubernetes/pki/etcd/ca.crt \
ETCDCTL_CERT=/etc/kubernetes/pki/etcd/server.crt \
ETCDCTL_KEY=/etc/kubernetes/pki/etcd/server.key \
etcdctl --endpoints=https://127.0.0.1:2379 snapshot save /var/lib/etcd/snapshot.db"

Check system logs

kubectl get events

Plugins for kubernetes:

https://github.com/kubernetes-sigs/krew/

Troubleshooting

https://kubernetes.io/docs/tasks/debug/debug-application/

https://kubernetes.io/docs/tasks/debug/debug-cluster/

https://kubernetes.io/docs/tasks/debug/debug-application/debug-pods/

https://kubernetes.io/docs/tasks/debug/debug-application/debug-service/

https://github.com/kubernetes/kubernetes/issues

https://kubernetes.slack.com/

Log file locations

journalctl -u kubelet | less

Control plane

sudo find / -name “apiserverlog”

/var/log/kube-apiserver.log /var/log/kube-scheduler.log /var/log/kube-controller-manager.log

/var/log/containers

/var/log/pods

Worker nodes

/var/log/kubelet.log /var/log/kube-proxy.log