DevOps Classroomnotes 27/Feb/2022

Storage

• K8s supports many types of Volumes
  • Ephemeral Volumes:
    • These volume exist as long as Pod Exists, But once Pod is destroyed this volume is also destroyed
  • Persistent Volumes (Storage Classes & Persisten Volume Claims):
    • This Volume exists beyond the lifetime of a Pod. K8s doesnot destroy persistent volumes
• In both the volumes k8s supports different volumes
  • azureDisk
  • azureFile
  • emptyDir
  • gcePersistentDisk
  • aws ebs
  • hostPath
  • local
  • nfs
• To understand Persistent Volumes Better, we need to understand
  • StorageClasses
  • Persistent Volume Claims
• A persistent Volume (PV) is a piece of storage in the cluster that has been provisioned by an adminstrator or it can be dynamically provisioned with StorageClasses.
• A PersistentVolumeClaim (PVC) is a request for storage by a user. Claims can request specific size and access modes
• Provisioning Storage
  • Static
  • Dynamic
• Lets Create a K8s Cluster in Azure: Refer Here
• Lets Create a K8s Cluster in AWS (Elastic Kubernetes Service):
  • Refer Here
  • To connect to AWS we need to create an IAM user Refer Here
  • Install aws cli Refer Here
    bash
sudo apt update
sudo apt install unzip -y
unzip awscliv2.zip
sudo ./aws/install
    
  • Install kubectl Refer Here
    curl -o kubectl https://amazon-eks.s3.us-west-2.amazonaws.com/1.21.2/2021-07-05/bin/linux/amd64/kubectl
sudo cp kubectl /usr/bin
sudo chmod 755 /usr/bin/kubectl
kubectl version
  • Installing eksctl Refer Here
    curl --silent --location "https://github.com/weaveworks/eksctl/releases/latest/download/eksctl_$(uname -s)_amd64.tar.gz" | tar xz -C /tmp
sudo mv /tmp/eksctl /usr/local/bin
eksctl version
  • Refer Here for eksctl documentation
  • Now lets create cluster using eksctl
    eksctl create cluster \
--name my-cluster \
--version 1.21 \
--without-nodegroup
    
    
• Note:
  • All the images from gitbash will be eks and from powershell will be aks
• Persistent Volumes
  • Official Docs: Refer Here
  • Types supported Refer Here
• Creating a Pod/Replication Controller/Deployment with PV, PVC and SC in Azure
  • Azure gives the default storage classes
    
  • Created a pvc
    
  • using the pvc claim in rs
    
  • Lets create a load balancer for testing purposes to connect to databse from location
    
  • Insert some data into database
    
  • Now delete replicaset
    
  • Now recreate the replicaset and view the data in the database
    
  • Refer Here for the manifests created for Azure
    
• Creating PVC on AWS EKS
  • Refer Here for the changes
• Note: Will create a document with resolution on storage

StatefulSet

• Stateful set manages Pods that are based on identical container spec.
• Stateful set maintains stick identity of their pods.
• These pods are created from same spec, but are not interchangable: each has a persistent identifier that it maintains across rescheduling