Kubeadm installation
- To fix the error with cri-socket we have used the following command
kubeadm init --pod-network-cidr=10.244.0.0/16 --cri-socket=unix:///var/run/cri-dockerd.sock
* The commands informed by k8s cluster are
Your Kubernetes control-plane has initialized successfully!
To start using your cluster, you need to run the following as a regular user:
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
Alternatively, if you are the root user, you can run:
export KUBECONFIG=/etc/kubernetes/admin.conf
You should now deploy a pod network to the cluster.
Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:
https://kubernetes.io/docs/concepts/cluster-administration/addons/
Then you can join any number of worker nodes by running the following on each as root:
kubeadm join 172.31.14.130:6443 --token zz7um7.dy22vb0xppw1jy05 \
--discovery-token-ca-cert-hash sha256:486c786fa26ee4e54144955a48cc1631082a14555622ac2818dc32438a104198
- Now for k8s networking the reference specification is CNI. There are many vendors who implement this. We are going to use flannel Refer Here for addons. For flannel Refer Here
- Now add the other node to k8s cluster using join command from above and also include –cri-socket
- Now setting up kubectl Refer Here
Kubernetes Workloads
- Pod:
- This is smallest unit of creation in k8s cluster
- Pods have container(s)
- Each Pod in k8s cluster gets a unique ip address
- All the containers in the Pod share the same network namespace.
Kubernetes api versioning
- To k8s cluster we directly or indirectly using kubectl speak with API Server
- k8s has lot of features underdevelopment, stable, improvements
- There are 3 channels for objects/features
- alpha
- beta
- stable
- To fill apiVersion the syntax
<api-group>/<version> - API Group is group of similar k8s objects
- If the api group is Core then
apiVersion: <version>
Kubernetes Objects
- Every thing in k8s is an object.
- To declare an object, we need to specify 4 fields
apiVersion:
kind:
metadata:
spec:
- K8s cluster will create and object and add an extra field called as status
apiVersion:
kind:
metadata:
spec:
status:
- kind is type of object
- metadata describes some additional information about object you are trying to create (name, labels)
- spec: This is the desired state
- To get all the api-resources in your k8s cluster
kubectl api-resources
