Let's look at what happens when we run kubeadm. This is exactly what kubeadm sets us up to do. It uses the API server but it doesn't depend on it so we can actually use the Kubelet to manage the control plane components. kubeadm and the kubeletįortunately, Kubernetes has a component called the Kubelet which manages containers running on a single host. This will make sure they are always running but won't make it easy to upgrade the components later. One way to make sure the control plane components are always running is to use systemd. But there are a number of things you have to think about, like how do you make sure each of them are always running? How do you update the components easily with as little impact to the system as possible? You could install them directly on the host machine by downloading them and running them but if they crash then you'd have to restart them manually. These components need to be installed on your master and can be installed in a number of ways. The API server depends on etcd so an etcd cluster is also required. The Kubernetes control plane consists of the Kubernetes API server ( kube-apiserver), controller manager ( kube-controller-manager), and scheduler ( kube-scheduler). The documentation for kubeadm outlines how to set up a cluster but as I was doing that I found how kubeadm actually sets up the master to be really interesting so I wanted to share that here. kubeadm really makes this easier so I suggest you give it a try. One of the most frequent criticisms of Kubernetes is that it's hard to install. Output should contain all the nodes with the etcd role and the output should be identical on all nodes.Kubeadm is a new tool that is part of the Kubernetes distribution as of 1.4.0 which helps you to install and set up a Kubernetes cluster. If any of the commands respond with Error: context deadline exceeded, the etcd instance is unhealthy (either quorum is lost or the instance is not correctly joined in the cluster) Check etcd Members on all Nodes If an internal address is configured for the host etcd is running on, the endpoint for etcdctl needs to be specified explicitly. The address where etcd is listening depends on the address configuration of the host etcd is running on. The node should be removed from the cluster, the state directory should be cleaned and the node should be re-added. The cluster state ( /var/lib/etcd) contains wrong information to join the cluster. The node should be removed from the cluster, and re-added. The node with the etcd instance logging rafthttp: request cluster ID mismatch is trying to join a cluster that has already been formed with another peer. The host firewall is preventing network communication. This can happen when the majority of the nodes running etcd go down/unreachable.Ĭonnection error: desc = "transport: Error while dialing dial tcp 0.0.0.0:2379: i/o timeout" Reconnecting to The etcd cluster has lost its quorum and is trying to establish a new leader. Check if the etcd container is running on the host with the address shown. Health check for peer xxx could not connect: dial tcp IP:2380: getsockopt: connection refusedĪ connection to the address shown on port 2380 cannot be established.
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