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kubernetes-cheat-sheet.md

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Kubernetes cheat sheet

useful links

tutorials

local playgrounds

remote playground and examples

tools

kubectl installation

curl -LO https://storage.googleapis.com/kubernetes-release/release/v1.17.4/bin/linux/amd64/kubectl
curl -LO https://storage.googleapis.com/kubernetes-release/release/v1.18.0/bin/linux/amd64/kubectl
  • kubectl autocompletion
source <(kubectl completion bash)
# source <(kubectl completion zsh)

or

# source /usr/share/bash-completion/bash_completion
kubectl completion bash >/etc/bash_completion.d/kubectl
  • trace logging
rm -rf ~/.kube/cache
kubectl get pods -v=6
kubectl get pods -v=7
kubectl get pods -v=8
# with specific context file from ~/.kube, specific config
kubectl --kubeconfig=config-rancher  get pods -v=8
  • explain yaml schema
kubectl explain pods
kubectl explain pods --recursive
kubectl explain pods --recursive --api-version=autoscaling/v2beta1
  • python client
pip install kubernetes

Architecture

architecture architecture architecture nodes with software kubernetes

workflow

deployment workflow

  1. The user deploys a new app by using the kubectl CLI. Kubectl sends the request to the API server.
  2. The API server receives the request and stores it in the data store (etcd). After the request is written to the data store, the API server is done with the request.
  3. Watchers detect the resource changes and send notifications to the Controller to act on those changes.
  4. The Controller detects the new app and creates new pods to match the desired number of instances. Any changes to the stored model will be used to create or delete pods.
  5. The Scheduler assigns new pods to a node based on specific criteria. The Scheduler decides on whether to run pods on specific nodes in the cluster. The Scheduler modifies the model with the node information.
  6. A Kubelet on a node detects a pod with an assignment to itself and deploys the requested containers through the container runtime, for example, Docker. Each node watches the storage to see what pods it is assigned to run. The node takes necessary actions on the resources assigned to it such as to create or delete pods.
  7. Kubeproxy manages network traffic for the pods, including service discovery and load balancing. Kubeproxy is responsible for communication between pods that want to interact.

kind

k3s

Lightweight Kubernetes distribution For resource-constrained environments ( IoT, Edge, Local-sandbox) Installation helpers:

  • K3D
  • k3sup
  • kubevip

microk8s

installation

sudo snap install microk8s --classic
sudo snap install microk8s --classic --edge

enable addons

microk8s.start
microk8s.enable dns dashboard

check installation

microk8s.inspect

check journals for services

journalctl -u snap.microk8s.daemon-docker
  • snap.microk8s.daemon-apiserver
  • snap.microk8s.daemon-controller-manager
  • snap.microk8s.daemon-scheduler
  • snap.microk8s.daemon-kubelet
  • snap.microk8s.daemon-proxy
  • snap.microk8s.daemon-docker
  • snap.microk8s.daemon-etcd

minikube

installation from snap

sudo snap install minikube

installation from release

curl -Lo minikube https://storage.googleapis.com/minikube/releases/latest/minikube-linux-amd64 && chmod +x minikube
curl -Lo kubectl https://storage.googleapis.com/kubernetes-release/release/$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt)/bin/linux/amd64/kubectl && chmod +x kubectl

export MINIKUBE_WANTUPDATENOTIFICATION=false
export MINIKUBE_WANTREPORTERRORPROMPT=false
export MINIKUBE_HOME=$HOME
export CHANGE_MINIKUBE_NONE_USER=true
mkdir $HOME/.kube || true
touch $HOME/.kube/config

# defalue kubernetes config file location
export KUBECONFIG=$HOME/.kube/config
sudo -E ./minikube start --vm-driver=none

# wait that Minikube has created
for i in {1..150}; do # timeout for 5 minutes
   ./kubectl get po &> /dev/null
   if [ $? -ne 1 ]; then
      break
  fi
  sleep 2
done

set up env

minikube completion bash

start

minikube start

uninstall kube, uninstall kubectl, uninstall minikube

kubectl delete node --all
kubectl delete pods --all
kubectl stop
kubectl delete

launchctl stop '*kubelet*.mount'
launchctl stop localkube.service
launchctl disable localkube.service

sudo kubeadm reset
## network cleaining up 
# sudo ip link del cni0
# sudo ip link del flannel.1
# sudo systemctl restart network

rm -rf ~/.kube ~/.minikube
sudo rm -rf /usr/local/bin/localkube /usr/local/bin/minikube
sudo rm -rf /etc/kubernetes/

# sudo apt-get purge kubeadm kubectl kubelet kubernetes-cni kube*
sudo apt-get purge kube*
sudo apt-get autoremove

docker system prune -af --volumes

start without VirtualBox/KVM

export MINIKUBE_WANTUPDATENOTIFICATION=false
export MINIKUBE_WANTREPORTERRORPROMPT=false
export MINIKUBE_HOME=$HOME
export CHANGE_MINIKUBE_NONE_USER=true

export KUBECONFIG=$HOME/.kube/config
sudo -E minikube start --vm-driver=none

kubectl using minikube context

permanently

kubectl config use-context minikube

temporary

kubectl get pods --context=minikube

example of started kube processes

/usr/bin/kubelet 
    --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf 
    --kubeconfig=/etc/kubernetes/kubelet.conf 
    --config=/var/lib/kubelet/config.yaml 
    --cgroup-driver=cgroupfs 
    --cni-bin-dir=/opt/cni/bin 
    --cni-conf-dir=/etc/cni/net.d 
    --network-plugin=cni 
    --resolv-conf=/run/systemd/resolve/resolv.conf 
    --feature-gates=DevicePlugins=true

kube-apiserver 
    --authorization-mode=Node,RBAC 
    --advertise-address=10.143.226.20 
    --allow-privileged=true 
    --client-ca-file=/etc/kubernetes/pki/ca.crt 
    --disable-admission-plugins=PersistentVolumeLabel 
    --enable-admission-plugins=NodeRestriction 
    --enable-bootstrap-token-auth=true 
    --etcd-cafile=/etc/kubernetes/pki/etcd/ca.crt 
    --etcd-certfile=/etc/kubernetes/pki/apiserver-etcd-client.crt --etcd-keyfile=/etc/kubernetes/pki/apiserver-etcd-client.key --etcd-servers=https://127.0.0.1:2379 --insecure-port=0 --kubelet-client-certificate=/etc/kubernetes/pki/apiserver-kubelet-client.crt --kubelet-client-key=/etc/kubernetes/pki/apiserver-kubelet-client.key --kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname --proxy-client-cert-file=/etc/kubernetes/pki/front-proxy-client.crt --proxy-client-key-file=/etc/kubernetes/pki/front-proxy-client.key --requestheader-allowed-names=front-proxy-client --requestheader-client-ca-file=/etc/kubernetes/pki/front-proxy-ca.crt --requestheader-extra-headers-prefix=X-Remote-Extra- --requestheader-group-headers=X-Remote-Group --requestheader-username-headers=X-Remote-User --secure-port=6443 --service-account-key-file=/etc/kubernetes/pki/sa.pub --service-cluster-ip-range=10.96.0.0/12 --tls-cert-file=/etc/kubernetes/pki/apiserver.crt --tls-private-key-file=/etc/kubernetes/pki/apiserver.key

kube-controller-manager
    --address=127.0.0.1
    --cluster-signing-cert-file=/etc/kubernetes/pki/ca.crt
    --cluster-signing-key-file=/etc/kubernetes/pki/ca.key
    --controllers=*,bootstrapsigner,tokencleaner
    --kubeconfig=/etc/kubernetes/controller-manager.conf
    --leader-elect=true
    --root-ca-file=/etc/kubernetes/pki/ca.crt
    --service-account-private-key-file=/etc/kubernetes/pki/sa.key
    --use-service-account-credentials=true

etcd
    --advertise-client-urls=https://127.0.0.1:2379
    --cert-file=/etc/kubernetes/pki/etcd/server.crt
    --client-cert-auth=true
    --data-dir=/var/lib/etcd
    --initial-advertise-peer-urls=https://127.0.0.1:2380
    --initial-cluster=gtxmachine0=https://127.0.0.1:2380
    --key-file=/etc/kubernetes/pki/etcd/server.key
    --listen-client-urls=https://127.0.0.1:2379
    --listen-peer-urls=https://127.0.0.1:2380
    --name=gtxmachine0
    --peer-cert-file=/etc/kubernetes/pki/etcd/peer.crt
    --peer-client-cert-auth=true
    --peer-key-file=/etc/kubernetes/pki/etcd/peer.key
    --peer-trusted-ca-file=/etc/kubernetes/pki/etcd/ca.crt
    --snapshot-count=10000
    --trusted-ca-file=/etc/kubernetes/pki/etcd/ca.crt

kube-scheduler 
    --address=127.0.0.1 
    --kubeconfig=/etc/kubernetes/scheduler.conf 
    --leader-elect=true

/usr/local/bin/kube-proxy 
    --config=/var/lib/kube-proxy/config.conf

/opt/bin/flanneld 
    --ip-masq 
    --kube-subnet-mgr

kubectl using different config file, kubectl config, different config kubectl

kubectl --kubeconfig=/home/user/.kube/config-student1 get pods

kubectl config with rancher, rancher with kubectl, rancher kubectl config

  • certificate-authority-data - from admin account
  • token - Bearer Token
apiVersion: v1
clusters:
- cluster:
    server: "https://10.14.22.20:9443/k8s/clusters/c-7w47z"
    certificate-authority-data: "....tLUVORCBDRVJUSUZJQ0FURS0tLS0t"
  name: "ev-cluster"

contexts:
- context:
    user: "ev-user"
    cluster: "ev-cluster"
  name: "ev-context"

current-context: "ev-context"

kind: Config
preferences: {}
users:
- name: "ev-user"
  user:  
    token: "token-6g4gv:lq4wbw4lmwtxkblmbbsbd7hc5j56v2ssjvfkxd"

install on ubuntu, install ubuntu, installation ubuntu, ubuntu installation

update software

# check accessible list
sudo apt list | grep kube
# update system info
sudo apt-get update
# install one package
sudo apt-get install -y kubeadm=1.18.2-00
# FROM ubuntu:18
# environment
sudo apt install docker.io
sudo systemctl enable docker
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add
sudo apt install curl
# kube
sudo apt-add-repository "deb http://apt.kubernetes.io/ kubernetes-xenial main"
sudo apt install kubeadm
sudo swapoff -a
# init for using flannel ( check inside kube-flannel.yaml section net-conf.json/Network )
sudo kubeadm init --pod-network-cidr=10.244.0.0/16
rm -rf $HOME/.kube
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
# !!! install flannel ( or weave.... )
# kubectl get nodes
```sh

# install via rancher
```bash
docker stop rancher
docker rm rancher

# -it --entrypoint="/bin/bash" \
docker run -d --restart=unless-stopped \
  --name rancher \
  -v /var/lib/rancher:/var/lib/rancher \
  -v /var/lib/rancher-log:/var/log \
  -p 9080:80 -p 9443:443 \
  -e HTTP_PROXY="http://qqml:mlfu\$1@proxy.muc:8080" \
  -e HTTPS_PROXY="http://qqml:mlfu\$1@proxy.muc:8080" \
  -e NO_PROXY="localhost,127.0.0.1,127.0.0.0/8,10.0.0.0/8,192.168.0.0/16" \
  rancher/rancher:latest

uninstall

cleanup node

# clean up for worker
## !!! most important !!!
sudo rm -rf /etc/cni/net.d

sudo rm -rf /opt/cni/bin
sudo rm -rf /var/lib/kubelet 
sudo rm -rf /var/lib/cni 
sudo rm -rf /etc/kubernetes
sudo rm -rf /run/calico 
sudo rm -rf /run/flannel 

sudo rm -rf /etc/ceph 
sudo rm -rf /opt/rke
sudo rm -rf /var/lib/calico 
sudo rm -rf /var/lib/etcd

sudo rm -rf /var/log/containers 
sudo rm -rf /var/log/pods 

# rancher full reset !!!
sudo rm -rf /var/lib/rancher/*
sudo rm -rf /var/lib/rancher-log/*

upgrade k8s

kube logs

### Master
## API Server, responsible for serving the API
/var/log/kube-apiserver.log 
## Scheduler, responsible for making scheduling decisions
/var/log/kube-scheduler.log
## Controller that manages replication controllers
/var/log/kube-controller-manager.log
### Worker Nodes
## Kubelet, responsible for running containers on the node
/var/log/kubelet.log
## Kube Proxy, responsible for service load balancing
/var/log/kube-proxy.log

kubernetes CLI

kubernetes version, k8s version

kubeadm version

one of the field will be like: GitVersion:"v1.11.1"

kubectl customization, parameters in separate files, kubectl templates

customization, templating, kustomize, parametrization 

kustomize build config/default | kubectl apply -f-

kubectl template, inline code

sed "s|<NODE_INSTANCE_IP>|$NODE_1_IP|" eks-localstorage.yaml-template >  | kubectl apply -f -

access cluster

  • reverse proxy activate proxy from current node 
    kubectl proxy --port 9090
# execute request against kubectl via reverse-proxy
curl {current node ip}:9090/api
  • token access 
    $TOKEN=$(kubectl describe secret $(kubectl get secrets | grep ^default | cut -f1 -d ' ') | grep -E '^token' | cut -f2 -d':' | tr -d " ")
echo $TOKEN | tee token.crt
echo "Authorization: Bearer "$TOKEN | tee token.header
# execute from remote node against ( cat ~/.kube/config | grep server )
curl https://{ip:port}/api --header @token.crt --insecure

connect to remote machine, rsh

# connect to remote machine
kubectl --namespace namespace-metrics --kubeconfig=config-rancher exec -ti sm-grafana-deployment-5bdb64-6dnb8 -- /bin/sh

check namespaces

kubectl get namespaces

at least three namespaces will be provided

default       Active    15m
kube-public   Active    15m
kube-system   Active    15m

create namespace

kubectl create namespace my-own-namespace

or via yaml file

kubectl apply -f {filename}
kind: Namespace
apiVersion: v1
metadata:
  name: test

create limits for namespace

example for previous namespace declaration

apiVersion: v1
kind: LimitRange
metadata:
  name: my-own-namespace
spec:
  limits:
  - default:
      memory: 512Mi
    defaultRequest:
      memory: 256Mi
    type: Container

limits for certain container

apiVersion: v1
kind: Pod
metadata:
  name: frontend
spec:
  containers:
  - name: db
    image: mysql
    env:
    - name: MYSQL_ROOT_PASSWORD
      value: "password"
    resources:
      requests:
        memory: "64Mi"
        cpu: "250m"
      limits:
        memory: "128Mi"
        cpu: "500m"

also can be limited: pods, pv/pvc, services, configmaps...

print limits

kubectl get quota --namespace my-own-namespace
kubectl describe quota/compute-quota --namespace my-own-namespace
kubectl describe quota/object-quota --namespace my-own-namespace

kubectl describe {pod-name} limits 
kubectl describe {pod-name} limits --namespace my-own-namespace

delete namespace

kubectl delete namespace {name of namespace}

users

  • normal user
    • client certificates
    • bearer tokens
    • authentication proxy
    • http basic authentication
    • OpenId
  • service user
    • service account tokens
    • credentials using secrets
    • specific to namespace
    • created by objects
    • anonymous user ( not authenticated )

exeternal applications, user management, managing users

rbac

ps aux | grep kube-apiserver
# expected output
# --authorization-mode=Node,RBAC
# read existing roles 
kubectl get clusterRoles
# describe roles created by permission-management
kubectl describe clusterRoles/template-namespaced-resources___developer
kubectl describe clusterRoles/template-namespaced-resources___operation

# get all rolebindings
kubectl get RoleBinding --all-namespaces
kubectl get ClusterRoleBinding  --all-namespaces
kubectl get rolebindings.rbac.authorization.k8s.io --all-namespaces


# describe one of bindings
kubectl describe ClusterRoleBinding/student1___template-cluster-resources___read-only
kubectl describe rolebindings.rbac.authorization.k8s.io/student1___template-namespaced-resources___developer___students --namespace students

Direct request to api, user management curl

TOKEN="Authorization: Basic YWRtaW46b2xnYSZ2aXRhbGlp"
curl -X GET -H "$TOKEN" http://localhost:4000/api/list-users

etcd

etcdctl installation

untar etcdctl from https://github.com/etcd-io/etcd/releases

etcd querying, etcd request key-values

docker exec -ti `docker ps | grep etcd | awk '{print $1}'` /bin/sh
etcdctl get / --prefix --keys-only
# etcdctl --endpoints=http://localhost:2379 get / --prefix --keys-only
etcdctl  get / --prefix --keys-only | grep permis
etcdctl  get /registry/namespaces/permission-manager -w=json

configuration, configmap

create configmap

example of configuration

color.ok=green
color.error=red
textmode=true
security.user.external.login_attempts=5

create configuration on cluster

kubectl create configmap my-config-file --from-env-file=/local/path/to/config.properties

will be created next configuration

...
data:
color.ok=green
color.error=red
textmode=true
security.user.external.login_attempts=5

or configuration with additional key, additional abstraction over the properties ( like Map of properties )

kubectl create configmap my-config-file --from-file=name-or-key-of-config=/local/path/to/config.properties

created file is:

data:
name-or-key-of-config:
    color.ok=green
    color.error=red
    textmode=true
    security.user.external.login_attempts=5

or configuration with additional key based on filename ( key will be a name of file )

kubectl create configmap my-config-file --from-file=/local/path/to/

created file is:

data:
config.properties:
    color.ok=green
    color.error=red
    textmode=true
    security.user.external.login_attempts=5

or inline creation

kubectl create configmap special-config --from-literal=color.ok=green --from-literal=color.error=red

get configurations, read configuration in specific format

kubectl get configmap 
kubectl get configmap --namespace kube-system 
kubectl get configmap --namespace kube-system kube-proxy --output json

using configuration, using of configmap

  • one variable from configmap 
    spec:
  containers:
    - name: test-container
      image: k8s.gcr.io/busybox
      command: [ "/bin/sh", "echo $(MY_ENVIRONMENT_VARIABLE)" ]
      env:
        - name: MY_ENVIRONMENT_VARIABLE
          valueFrom:
            configMapKeyRef:
              name: my-config-file
              key: security.user.external.login_attempts
  • all variables from configmap 
    ...
     envFrom:
     - configMapRef:
         name: my-config-file

cluster information

kubectl cluster-info
kubectl cluster-info dump

start readiness, check cluster

kubectl get node
kubectl get pods
minikube dashboard

addons

minikube addons list
minikube addons enable ingress

labels

show labels for each node

kubectl get nodes --show-labels

add label to Node

kubectl label nodes {node name} my_label=my_value

remove label from Node

kubectl label nodes {node name} my_label-

deployment

to see deployment from external world, remote access to pod, deployment access:
user ----> Route -----> Service ----> Deployment main schema

start dummy container

kubectl run hello-minikube --image=k8s.gcr.io/echoserver:1.4 --port=8080

start ubuntu and open shell

kubectl run --restart=Never --rm -it --image=ubuntu --limits='memory=123Mi' -- sh

create deployment ( with replica set )

kubectl run http --image=katacoda/docker-http-server:latest --replicas=1

scale deployment

deployment_name=my_deployment_name
## scale pod to amount of replicas
kubectl scale --replicas=3 deployment $deployment_name

## conditional scaling 
kubectl autoscale deployment $deployment_name --cpu-percent=50 --min=1 --max=3
# check Horizonal Pod Autoscaling
kubectl get hpa

create from yaml file

kubectl create -f /path/to/controller.yml

create/update yaml file

kubectl apply -f /path/to/controller.yml

create service, expose service, inline service fastly

kubectl expose deployment helloworld-deployment --type=NodePort --name=helloworld-service
kubectl expose deployment helloworld-deployment --external-ip="172.17.0.13" --port=8000 --target-port=80

port forwarding, expose service

kubectl port-forward svc/my_service 8080 --namespace my_namespace

reach out service

minikube service helloworld-service
minikube service helloworld-service --url

service port range

kube-apiserver --service-node-port-range=30000-40000

describe resources, information about resources, inspect resources, inspect pod

kubectl describe deployment {name of deployment}
kubectl describe service {name of service}
kubectl describe pod {name of the pod}

describe users, user token

kubectl --namespace kube-system describe secret admin-user

get resources

kubectl get all --all-namespaces
# check pod statuses 
kubectl get pods
kubectl get pods --namespace kube-system
kubectl get pods --show-labels
kubectl get pods --output=wide --selector="run=load-balancer-example" 
kubectl get pods --namespace training --field-selector="status.phase==Running,status.phase!=Unknown"
kubectl get service --output=wide
kubectl get service --output=wide --selector="app=helloworld"
kubectl get deployments
kubectl get replicasets
kubectl get nodes
kubectl get cronjobs
kubectl get daemonsets
kubectl get pods,deployments,services,rs,cm,pv,pvc -n demo

kubectl list services
kubectl describe service my_service_name

determinate cluster 'hostIP' to reach out application(s)

minikube ip

open 'kube-dns-....'/hostIP open 'kube-proxy-....'/hostIP

edit configuration of controller

kubectl edit pod hello-minikube-{some random hash}
kubectl edit deploy hello-minikube
kubectl edit ReplicationControllers helloworld-controller
kubectl set image deployment/helloworld-deployment {name of image}

rollout status

kubectl rollout status  deployment/helloworld-deployment

rollout history

kubectl rollout history  deployment/helloworld-deployment
kubectl rollout undo deployment/helloworld-deployment
kubectl rollout undo deployment/helloworld-deployment --to-revision={number of revision from 'history'}

delete running container

kubectl delete pod hello-minikube-6c47c66d8-td9p2

delete deployment

kubectl delete deploy hello-minikube

delete ReplicationController

kubectl delete rc helloworld-controller

delete PV/PVC

oc delete pvc/pvc-scenario-output-prod

port forwarding from local to pod/deployment/service

next receipts allow to redirect 127.0.0.1:8080 to pod:6379

kubectl port-forward redis-master-765d459796-258hz      8080:6379 
kubectl port-forward pods/redis-master-765d459796-258hz 8080:6379
kubectl port-forward deployment/redis-master            8080:6379 
kubectl port-forward rs/redis-master                    8080:6379 
kubectl port-forward svc/redis-master                   8080:6379

NodeSelector for certain host

spec:
   template:
      spec:
         nodeSelector: 
            kubernetes.io/hostname: gtxmachine1-ev

persistent volume

kind: PersistentVolume
apiVersion: v1
metadata:
  name: pv-volume3
  labels:
    type: local
spec:
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/mnt/data3"

to access created volume

ls /mnt/data3

list of existing volumes

kubectl get pv 
kubectl get pvc

container lifecycle

apiVersion: v1
kind: Pod
metadata:
  name: lifecycle-demo
spec:
  containers:
  - name: lifecycle-demo-container
    image: nginx
    lifecycle:
      postStart:
        exec:
          command: ["/bin/sh", "-c", "echo Hello from the postStart handler > /usr/share/message"]
      preStop:
        exec:
          command: ["/bin/sh","-c","nginx -s quit; while killall -0 nginx; do sleep 1; done"]
containers:
  - name: lifecycle
    image: busybox
    lifecycle:
      postStart:
        exec:
          command:
            - "touch"
            - "/var/log/lifecycle/post-start"
      preStop:
        httpGet:
          path: "/abort"
          port: 8080

Serverless

  • OpenFaas
  • Kubeless
  • Fission
  • OpenWhisk

deploy Pod on Node with label

apiVersion: v1
kind: Pod
metadata:
...
spec:
...
  nodeSelector:
    my_label=my_value

create Deployment for specific node

apiVersion: some-version
kind: Deployment
metadata:
...
spec:
...
  nodeSelector:
    my_label=my_value

resolving destination node

when label was not found

  • nodeAffinity
    • preferred - deploy in any case, with preferrence my_label=my_value
spec:
  affinity:
    nodeAffinity:
      preferredDuringSchedulingIgnoredDuringExecution:
      - weight: 1
        preference:
          matchExpressions:
          - key: my_label
            operator: In
            values:
            - my_value
  • required - deploy only when label matched my_label=my_value
spec:
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
        - matchExpressions:
          - key: my_label
            operator: In
            values:
            - my_value
  • nodeAntiAffinity
spec:
  affinity:
    nodeAntiAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
  • podAffinity
    • preferred spec.affinity.podAffinity.preferredDuringSchedulingIgnoredDuringExecution
    • required spec.affinity.podAffinity.requiredDuringSchedulingIgnoredDuringExecution
  • podAntiAffinity
    • preferred spec.affinity.podAntiAffinity.preferredDuringSchedulingIgnoredDuringExecution
    • required spec.affinity.podAntiAffinity.requiredDuringSchedulingIgnoredDuringExecution

delete node from cluster

kubectl get nodes
kubectl delete {node name}

add node to cluster

ssh {master node}
kubeadm token create --print-join-command  --ttl 0

expected result from previous command

kubeadm join 10.14.26.210:6443 --token 7h0dmx.2v5oe1jwed --discovery-token-ca-cert-hash sha256:1d28ebf950316b8f3fdf680af5619ea2682707f2e966fc0

go to node, clean up and apply token

ssh {node address}
# hard way: rm -rf /etc/kubernetes
kubeadm reset
# apply token from previous step with additional flag: --ignore-preflight-errors=all
kubeadm join 10.14.26.210:6443 --token 7h0dmx.2v5oe1jwed --discovery-token-ca-cert-hash sha256:1d28ebf950316b8f3fdf680af5619ea2682707f2e966fc0 --ignore-preflight-errors=all

expected result from previous command

...
This node has joined the cluster:
* Certificate signing request was sent to master and a response
  was received.
* The Kubelet was informed of the new secure connection details.
 
Run 'kubectl get nodes' on the master to see this node join the cluster.

next block is not mandatory in most cases

systemctl restart kubelet

logs

kubectl logs <name of pod>

create dashboard

kubectl create -f https://raw.githubusercontent.com/kubernetes/dashboard/master/aio/deploy/recommended/kubernetes-dashboard.yaml

access dashboard

kubectl -n kube-system describe secret admin-user
http://127.0.0.1:8001/api/v1/namespaces/kube-system/services/https:kubernetes-dashboard:/proxy/#!/overview?namespace=default
kubectl proxy

common

execute command on specific pod

kubectl exec -it {name of a pod}  -- bash -c "echo hi > /path/to/output/test.txt"

Extending

custom controller

Weave

kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')"

Flannel

deployment diagram restart nodes

# remove died pods
kubectl delete pods kube-flannel-ds-amd64-zsfz  --grace-period=0 --force
# delete all resources from file and ignore not found
kubectl delete -f --ignore-not-found https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
kubectl create  -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

install flannel

### apply this with possible issue with installation: 
## kube-flannel.yml": daemonsets.apps "kube-flannel-ds-s390x" is forbidden: User "system:node:name-of-my-server" cannot get daemonsets.apps in the namespace "kube-system"
# sudo kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/a70459be0084506e4ec919aa1c114638878db11b/Documentation/kube-flannel.yml

## Container runtime network not ready: NetworkReady=false reason:NetworkPluginNotReady message:docker: network plugin is not ready: cni config uninitialized
# sudo kubectl -n kube-system apply -f https://raw.githubusercontent.com/coreos/flannel/bc79dd1505b0c8681ece4de4c0d86c5cd2643275/Documentation/kube-flannel.yml

## print all logs
journalctl -f -u kubelet.service
# $KUBELET_NETWORK_ARGS in 
# /etc/systemd/system/kubelet.service.d/10-kubeadm.conf

## ideal way, not working properly in most cases
sudo kubectl -n kube-system apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

## check installation 
ps aux | grep flannel
# root     13046  0.4  0.0 645968 24748 ?        Ssl  10:49   0:00 /opt/bin/flanneld --ip-masq --kube-subnet-mgr

ifconfig
cni0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        inet 10.244.0.1  netmask 255.255.255.0  broadcast 0.0.0.0
flannel.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1450
        inet 10.244.0.0  netmask 255.255.255.255  broadcast 0.0.0.0

change settings and restart

kubectl edit cm kube-flannel-cfg -n kube-system
# net-conf.json: | { "Network": "10.244.0.0/16", "Backend": { "Type": "vxlan" } }

# Wipe current CNI network interfaces remaining the old network pool:
sudo ip link del cni0; sudo ip link del flannel.1

# Re-spawn Flannel and CoreDNS pods respectively:
kubectl delete pod --selector=app=flannel -n kube-system
kubectl delete pod --selector=k8s-app=kube-dns -n kube-system

# waiting for restart of all services

read logs

kubectl logs --namespace kube-system kube-flannel-ds-amd64-j4frw -c kube-flannel

read logs from all pods

for each_node in $(kubectl get pods --namespace kube-system | grep flannel | awk '{print $1}');do echo $each_node;kubectl logs --namespace kube-system $each_node -c kube-flannel;done

read settings

kubectl --namespace kube-system exec kube-flannel-ds-amd64-wc4zp ls /etc/kube-flannel/
kubectl --namespace kube-system exec kube-flannel-ds-amd64-wc4zp cat /etc/kube-flannel/cni-conf.json
kubectl --namespace kube-system exec kube-flannel-ds-amd64-wc4zp cat /etc/kube-flannel/net-conf.json

kubectl --namespace kube-system exec kube-flannel-ds-amd64-wc4zp ls /run/flannel/
kubectl --namespace kube-system exec kube-flannel-ds-amd64-wc4zp cat /run/flannel/subnet.env

kubectl --namespace kube-system exec kube-flannel-ds-amd64-wc4zp ls /etc/cni/net.d
kubectl --namespace kube-system exec kube-flannel-ds-amd64-wc4zp cat /etc/cni/net.d/10-flannel.conflist

read DNS logs

kubectl get svc --namespace=kube-system | grep kube-dns
kubectl logs --namespace=kube-system coredns-78fcd94-7tlpw | tail

simple POD, dummy pod, waiting pod

kind: Pod
apiVersion: v1
metadata:
  name: sleep-dummy-pod
  namespace: students
spec:
  containers:
    - name: sleep-dummy-pod
      image: ubuntu
      command: ["/bin/bash", "-ec", "while :; do echo '.'; sleep 3600 ; done"]
  restartPolicy: Never

NFS ( Network File System )

nfs server

# nfs server 
vim /etc/exports
# /mnt/disks/k8s-local-storage/nfs        10.55.0.0/16(rw,sync,no_subtree_check)
# /mnt/disks/k8s-local-storage1/nfs       10.55.0.0/16(rw,sync,no_subtree_check)

sudo exportfs -a
sudo exportfs -v

systemctl status nfs-server
ll /sys/module/nfs/parameters/
ll /sys/module/nfsd/parameters/
sudo blkid
sudo vim /etc/fstab
# UUID=35c71cfa-6ee2-414a-5555-effc30555555 /mnt/disks/k8s-local-storage ext4 defaults 0 0
# UUID=42665716-1f89-44d4-5555-37b207555555 /mnt/disks/k8s-local-storage1 ext4 defaults 0 0
nfsstat

master. mount volume ( nfs server )

# create point 
sudo mkdir /mnt/disks/k8s-local-storage1
# mount 
sudo mount /dev/sdc /mnt/disks/k8s-local-storage1
sudo chmod 755 /mnt/disks/k8s-local-storage1
# createlink 
sudo ln -s /mnt/disks/k8s-local-storage1/nfs /mnt/nfs1
ls -la /mnt/disks
ls -la /mnt

# update storage
sudo cat /etc/exports
# /mnt/disks/k8s-local-storage1/nfs       10.55.0.0/16(rw,sync,no_subtree_check)

# restart 
sudo exportfs -a
sudo exportfs -v

nfs client

sudo blkid

sudo mkdir /mnt/nfs1
sudo chmod 777 /mnt/nfs1

sudo vim /etc/fstab
# add record
# 10.55.0.3:/mnt/disks/k8s-local-storage1/nfs /mnt/nfs1 nfs rw,noauto,x-systemd.automount,x-systemd.device-timeout=10,timeo=14 0 0
10.55.0.3:/mnt/disks/k8s-local-storage1/nfs /mnt/nfs1 nfs defaults 0 0

# refresh fstab
sudo mount -av

# for server 
ls /mnt/disks/k8s-local-storage
ls /mnt/disks/k8s-local-storage1

# for clients
ls /mnt/disks/k8s-local-storage1

trouble shooting, problem resolving

POD_NAME=service-coworking-postgresql-0

kubectl get pod $POD_NAME -o json
kubectl describe pod $POD_NAME

kubectl get --watch events
kubectl get events --sort-by=.metadata.creationTimestamp
kubectl get events --field-selector type=Warning
kubectl get events --field-selector type=Error
kubectl get events --field-selector type=Critical

kubectl get pvc data-service-coworking-postgresql-0 -o json

postgresql waiting for a volume to be created

create provider

kubectl get all -l app.kubernetes.io/name=aws-ebs-csi-driver -n kube-system

certificate is expired

bootstrap.go:195] Part of the existing bootstrap client certificate is expired: 2019-08-22 11:29:48 +0000 UTC

solution

sudo cat /etc/systemd/system/kubelet.service.d/10-kubeadm.conf

# archive configuration
sudo cp /etc/kubernetes/pki /etc/kubernetes/pki_backup
sudo mkdir /etc/kubernetes/conf_backup
sudo cp /etc/kubernetes/*.conf /etc/kubernetes/conf_backup

# remove certificates
sudo rm /etc/kubernetes/pki/./apiserver-kubelet-client.crt 
sudo rm /etc/kubernetes/pki/./etcd/healthcheck-client.crt 
sudo rm /etc/kubernetes/pki/./etcd/server.crt 
sudo rm /etc/kubernetes/pki/./etcd/peer.crt 
sudo rm /etc/kubernetes/pki/./etcd/ca.crt 
sudo rm /etc/kubernetes/pki/./front-proxy-client.crt 
sudo rm /etc/kubernetes/pki/./apiserver-etcd-client.crt 
sudo rm /etc/kubernetes/pki/./front-proxy-ca.crt 
sudo rm /etc/kubernetes/pki/./apiserver.crt 
sudo rm /etc/kubernetes/pki/./ca.crt 
sudo rm /etc/kubernetes/pki/apiserver.crt 
sudo rm /etc/kubernetes/pki/apiserver-etcd-client.crt 
sudo rm /etc/kubernetes/pki/apiserver-kubelet-client.crt 
sudo rm /etc/kubernetes/pki/ca.crt 
sudo rm /etc/kubernetes/pki/front-proxy-ca.crt 
sudo rm /etc/kubernetes/pki/front-proxy-client.crt 

# remove configurations
sudo rm /etc/kubernetes/apiserver-kubelet-client.*
sudo rm /etc/kubernetes/front-proxy-client.*
sudo rm /etc/kubernetes/etcd/*
sudo rm /etc/kubernetes/apiserver-etcd-client.*
sudo rm /etc/kubernetes/admin.conf
sudo rm /etc/kubernetes/controller-manager.conf
sudo rm /etc/kubernetes/kubelet.conf
sudo rm /etc/kubernetes/scheduler.conf

# re-init certificates
sudo kubeadm init phase certs all --apiserver-advertise-address {master ip address} --ignore-preflight-errors=all

# re-init configurations
sudo kubeadm init phase kubeconfig all --ignore-preflight-errors=all

# re-start
sudo systemctl stop kubectl.service
sudo systemctl restart docker.service
docker system prune -af --volumes
reboot

# /usr/bin/kubelet
sudo systemctl start kubectl.service

# init locate kubectl
sudo cp /etc/kubernetes/admin.conf ~/.kube/config

# check certificate
openssl x509 -in /etc/kubernetes/pki/apiserver.crt  -noout -text  | grep "Not After"

template frameworks

Troubleshooting

issue with PV / PVC

pod has unbound immediate PersistentVolumeClaims. preemption: 0/2 nodes are available: 2 No preemption victims found for incoming pod..

create - check PV & PVC capacities (requested space) - PVC should have not more than PV