instruction: Create a comprehensive Dockerfile for cluster applications with best practices
output: ```dockerfile
  from the droplet:
  curl http://169.254.169.254/metadata/v1/interfaces/public/0/anchor_ipv4/address
  The workaround is to tell kubelet which IP to use using --node-ip.
  When using DigitalOcean, it can be the public one (assigned to eth0) or
  the private one (assigned to eth1) should you want to use the optional
  private network. The kubeletExtraArgs section of the kubeadm
  NodeRegistrationOptions structure
  can be used for this.
  Then restart kubelet:
  systemctl daemon-reload
  systemctl restart kubelet
  
  coredns pods have CrashLoopBackOff or Error state
  If you have nodes that are running SELinux with an older version of Docker, you might experience a scenario
  where the coredns pods are not starting. To solve that, you can try one of the following options:
  
  Upgrade to a newer version of Docker.
  
  Disable SELinux.
  
  Modify the coredns deployment to set allowPrivilegeEscalation to true:
  
  kubectl -n kube-system get deployment coredns -o yaml | \
   sed 's/allowPrivilegeEscalation: false/allowPrivilegeEscalation: true/g' | \
   kubectl apply -f -
  Another cause for CoreDNS to have CrashLoopBackOff is when a CoreDNS Pod deployed in Kubernetes detects a loop.
  A number of workarounds
  are available to avoid Kubernetes trying to restart the CoreDNS Pod every time CoreDNS detects the loop and exits.
  
  Warning: Disabling SELinux or setting allowPrivilegeEscalation to true can compromise
  the security of your cluster.
  
  etcd pods restart continually
  If you encounter the following error:
  rpc error: code = 2 desc = oci runtime error: exec failed: container_linux.go:247: starting container process caused "process_linux.go:110: decoding init error
  ```