kubeadm init  --pod-network-cidr=10.244.0.0/16 --kubernetes-version=1.15.3

error execution phase preflight: [preflight] Some fatal errors occurred:
        [ERROR SystemVerification]: unsupported graph driver: btrfs
    [preflight] If you know what you are doing, you can make a check non-fatal with `--ignore-preflight-errors=...`

{
  "storage-driver": "btrfs"
}