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Setup

Instructions for setting up a Kubernetes cluster.

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Using kubeadm to Create a Cluster

This quickstart shows you how to easily install a Kubernetes cluster on machines running Ubuntu 16.04+, CentOS 7 or HypriotOS v1.0.1+. The installation uses a tool called kubeadm which is part of Kubernetes. As of v1.6, kubeadm aims to create a secure cluster out of the box via mechanisms such as RBAC.

This process works with local VMs, physical servers and/or cloud servers. It is simple enough that you can easily integrate its use into your own automation (Terraform, Chef, Puppet, etc).

See the full kubeadm reference for information on all kubeadm command-line flags and for advice on automating kubeadm itself.

kubeadm assumes you have a set of machines (virtual or real) that are up and running. It is designed to be part of a large provisioning system - or just for easy manual provisioning. kubeadm is a great choice where you have your own infrastructure (e.g. bare metal), or where you have an existing orchestration system (e.g. Puppet) that you have to integrate with.

If you are not constrained, there are other higher-level tools built to give you complete clusters:

kubeadm Maturity

Aspect Maturity Level
Command line UX beta
Config file alpha
Self-hosting alpha
kubeadm alpha commands alpha
Implementation beta

The experience for the command line is currently in beta and we are trying hard not to change command line flags and break that flow. Other parts of the experience are still under active development. The implementation may change slightly as the tool evolves to support even easier upgrades and high availability (HA). Any commands under kubeadm alpha (not documented here) are, of course, alpha.

Be sure to read the limitations. Specifically, configuring cloud providers is difficult.

Before you begin

  1. One or more machines running Ubuntu 16.04+, CentOS 7 or HypriotOS v1.0.1+
  2. 2 GB or more of RAM per machine (any less will leave little room for your apps)
  3. 2 CPUs or more on the master
  4. Full network connectivity between all machines in the cluster (public or private network is fine)

Objectives

Instructions

(1/4) Installing kubeadm on your hosts

See Installing kubeadm.

Note: If you already have kubeadm installed, you should do a apt-get update && apt-get upgrade or yum update to get the latest version of kubeadm.

The kubelet is now restarting every few seconds, as it waits in a crashloop for kubeadm to tell it what to do.

(2/4) Initializing your master

The master is the machine where the control plane components run, including etcd (the cluster database) and the API server (which the kubectl CLI communicates with).

To initialize the master, pick one of the machines you previously installed kubeadm on, and run:

kubeadm init

Notes:

The output should look like:

[kubeadm] WARNING: kubeadm is in beta, please do not use it for production clusters.
[init] Using Kubernetes version: v1.8.0
[init] Using Authorization modes: [Node RBAC]
[preflight] Running pre-flight checks
[kubeadm] WARNING: starting in 1.8, tokens expire after 24 hours by default (if you require a non-expiring token use --token-ttl 0)
[certificates] Generated ca certificate and key.
[certificates] Generated apiserver certificate and key.
[certificates] apiserver serving cert is signed for DNS names [kubeadm-master kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 10.138.0.4]
[certificates] Generated apiserver-kubelet-client certificate and key.
[certificates] Generated sa key and public key.
[certificates] Generated front-proxy-ca certificate and key.
[certificates] Generated front-proxy-client certificate and key.
[certificates] Valid certificates and keys now exist in "/etc/kubernetes/pki"
[kubeconfig] Wrote KubeConfig file to disk: "admin.conf"
[kubeconfig] Wrote KubeConfig file to disk: "kubelet.conf"
[kubeconfig] Wrote KubeConfig file to disk: "controller-manager.conf"
[kubeconfig] Wrote KubeConfig file to disk: "scheduler.conf"
[controlplane] Wrote Static Pod manifest for component kube-apiserver to "/etc/kubernetes/manifests/kube-apiserver.yaml"
[controlplane] Wrote Static Pod manifest for component kube-controller-manager to "/etc/kubernetes/manifests/kube-controller-manager.yaml"
[controlplane] Wrote Static Pod manifest for component kube-scheduler to "/etc/kubernetes/manifests/kube-scheduler.yaml"
[etcd] Wrote Static Pod manifest for a local etcd instance to "/etc/kubernetes/manifests/etcd.yaml"
[init] Waiting for the kubelet to boot up the control plane as Static Pods from directory "/etc/kubernetes/manifests"
[init] This often takes around a minute; or longer if the control plane images have to be pulled.
[apiclient] All control plane components are healthy after 39.511972 seconds
[uploadconfig] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[markmaster] Will mark node master as master by adding a label and a taint
[markmaster] Master master tainted and labelled with key/value: node-role.kubernetes.io/master=""
[bootstraptoken] Using token: <token>
[bootstraptoken] Configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials
[bootstraptoken] Configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token
[bootstraptoken] Creating the "cluster-info" ConfigMap in the "kube-public" namespace
[addons] Applied essential addon: kube-dns
[addons] Applied essential addon: kube-proxy

Your Kubernetes master has initialized successfully!

To start using your cluster, you need to run (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

You should now deploy a pod network to the cluster.
Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:
  http://kubernetes.io/docs/admin/addons/

You can now join any number of machines by running the following on each node
as root:

  kubeadm join --token <token> <master-ip>:<master-port> --discovery-token-ca-cert-hash sha256:<hash>

To make kubectl work for your non-root user, you might want to run these commands (which is also a part of the kubeadm init output):

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 could run this:

export KUBECONFIG=/etc/kubernetes/admin.conf

Make a record of the kubeadm join command that kubeadm init outputs. You will need this in a moment.

The token is used for mutual authentication between the master and the joining nodes. The token included here is secret, keep it safe — anyone with this token can add authenticated nodes to your cluster. These tokens can be listed, created and deleted with the kubeadm token command. See the reference guide.

(3/4) Installing a pod network

You must install a pod network add-on so that your pods can communicate with each other.

The network must be deployed before any applications. Also, kube-dns, a helper service, will not start up before a network is installed. kubeadm only supports Container Network Interface (CNI) based networks (and does not support kubenet).

Several projects provide Kubernetes pod networks using CNI, some of which also support Network Policy. See the add-ons page for a complete list of available network add-ons.

New for Kubernetes 1.6: kubeadm 1.6 sets up a more secure cluster by default. As such it uses RBAC to grant limited privileges to workloads running on the cluster. This includes networking integrations. As such, ensure that you are using a network system that has been updated to run with 1.6 and RBAC.

You can install a pod network add-on with the following command:

kubectl apply -f <add-on.yaml>

NOTE: You can install only one pod network per cluster.

Please select one of the tabs to see installation instructions for the respective third-party Pod Network Provider.

Refer to the Calico documentation for a kubeadm quickstart, a kubeadm installation guide, and other resources.

Note:

  • In order for Network Policy to work correctly, you need to pass --pod-network-cidr=192.168.0.0/16 to kubeadm init.
  • Calico works on amd64 only.
kubectl apply -f https://docs.projectcalico.org/v2.6/getting-started/kubernetes/installation/hosted/kubeadm/1.6/calico.yaml

The official Canal set-up guide is here.

Note:

  • For Canal to work correctly, --pod-network-cidr=10.244.0.0/16 has to be passed to kubeadm init.
  • Canal works on amd64 only.
kubectl apply -f https://raw.githubusercontent.com/projectcalico/canal/master/k8s-install/1.7/rbac.yaml
kubectl apply -f https://raw.githubusercontent.com/projectcalico/canal/master/k8s-install/1.7/canal.yaml

Note:

  • For flannel to work correctly, --pod-network-cidr=10.244.0.0/16 has to be passed to kubeadm init.
  • flannel works on amd64, arm, arm64 and ppc64le, but for it to work on a platform other than amd64 you have to manually download the manifest and replace amd64 occurences with your chosen platform.
  • Set /proc/sys/net/bridge/bridge-nf-call-iptables to 1 by running sysctl net.bridge.bridge-nf-call-iptables=1 to pass bridged IPv4 traffic to iptables’ chains. This is a requirement for some CNI plugins to work, for more information please see here.
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/v0.9.1/Documentation/kube-flannel.yml
  • For more information about flannel, please see here.

Set /proc/sys/net/bridge/bridge-nf-call-iptables to 1 by running sysctl net.bridge.bridge-nf-call-iptables=1 to pass bridged IPv4 traffic to iptables’ chains. This is a requirement for some CNI plugins to work, for more information please see here.

Kube-router relies on kube-controll-manager to allocate pod CIDR for the nodes. Therefore, use kubeadm init with the --pod-network-cidr flag.

Kube-router provides pod networking, network policy, and high-performing IP Virtual Server(IPVS)/Linux Virtual Server(LVS) based service proxy.

For information on setting up Kubernetes cluster with Kube-router using kubeadm, please see official setup guide.

Set /proc/sys/net/bridge/bridge-nf-call-iptables to 1 by running sysctl net.bridge.bridge-nf-call-iptables=1 to pass bridged IPv4 traffic to iptables’ chains. This is a requirement for some CNI plugins to work, for more information please see here.

The official Romana set-up guide is here.

Note: Romana works on amd64 only.

kubectl apply -f https://raw.githubusercontent.com/romana/romana/master/containerize/specs/romana-kubeadm.yml

Set /proc/sys/net/bridge/bridge-nf-call-iptables to 1 by running sysctl net.bridge.bridge-nf-call-iptables=1 to pass bridged IPv4 traffic to iptables’ chains. This is a requirement for some CNI plugins to work, for more information please see here.

The official Weave Net set-up guide is here.

Note: Weave Net works on amd64, arm and arm64 without any extra action required. Weave Net sets hairpin mode by default. This allows Pods to access themselves via their Service IP address if they don’t know their PodIP.

export kubever=$(kubectl version | base64 | tr -d '\n')
kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$kubever"

Once a pod network has been installed, you can confirm that it is working by checking that the kube-dns pod is Running in the output of kubectl get pods --all-namespaces. And once the kube-dns pod is up and running, you can continue by joining your nodes.

If your network is not working or kube-dns is not in the Running state, check out our troubleshooting docs.

Master Isolation

By default, your cluster will not schedule pods on the master for security reasons. If you want to be able to schedule pods on the master, e.g. for a single-machine Kubernetes cluster for development, run:

kubectl taint nodes --all node-role.kubernetes.io/master-

With output looking something like:

node "test-01" untainted
taint key="dedicated" and effect="" not found.
taint key="dedicated" and effect="" not found.

This will remove the node-role.kubernetes.io/master taint from any nodes that have it, including the master node, meaning that the scheduler will then be able to schedule pods everywhere.

(4/4) Joining your nodes

The nodes are where your workloads (containers and pods, etc) run. To add new nodes to your cluster do the following for each machine:

The output should look something like:

[kubeadm] WARNING: kubeadm is in beta, please do not use it for production clusters.
[preflight] Running pre-flight checks
[discovery] Trying to connect to API Server "10.138.0.4:6443"
[discovery] Created cluster-info discovery client, requesting info from "https://10.138.0.4:6443"
[discovery] Requesting info from "https://10.138.0.4:6443" again to validate TLS against the pinned public key
[discovery] Cluster info signature and contents are valid and TLS certificate validates against pinned roots, will use API Server "10.138.0.4:6443"
[discovery] Successfully established connection with API Server "10.138.0.4:6443"
[bootstrap] Detected server version: v1.8.0
[bootstrap] The server supports the Certificates API (certificates.k8s.io/v1beta1)
[csr] Created API client to obtain unique certificate for this node, generating keys and certificate signing request
[csr] Received signed certificate from the API server, generating KubeConfig...

Node join complete:
* Certificate signing request sent to master and response
  received.
* Kubelet informed of new secure connection details.

Run 'kubectl get nodes' on the master to see this machine join.

A few seconds later, you should notice this node in the output from kubectl get nodes when run on the master.

(Optional) Controlling your cluster from machines other than the master

In order to get a kubectl on some other computer (e.g. laptop) to talk to your cluster, you need to copy the administrator kubeconfig file from your master to your workstation like this:

scp root@<master ip>:/etc/kubernetes/admin.conf .
kubectl --kubeconfig ./admin.conf get nodes

Note: If you are using GCE, instances disable ssh access for root by default. If that’s the case you can log in to the machine, copy the file someplace that can be accessed and then use gcloud compute copy-files.

(Optional) Proxying API Server to localhost

If you want to connect to the API Server from outside the cluster you can use kubectl proxy:

scp root@<master ip>:/etc/kubernetes/admin.conf .
kubectl --kubeconfig ./admin.conf proxy

You can now access the API Server locally at http://localhost:8001/api/v1

(Optional) Installing a sample application

Now it is time to take your new cluster for a test drive. Sock Shop is a sample microservices application that shows how to run and connect a set of services on Kubernetes. To learn more about the sample microservices app, see the GitHub README.

Note that the Sock Shop demo only works on amd64.

kubectl create namespace sock-shop
kubectl apply -n sock-shop -f "https://github.com/microservices-demo/microservices-demo/blob/master/deploy/kubernetes/complete-demo.yaml?raw=true"

You can then find out the port that the NodePort feature of services allocated for the front-end service by running:

kubectl -n sock-shop get svc front-end

Sample output:

NAME        CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE
front-end   10.110.250.153   <nodes>       80:30001/TCP   59s

It takes several minutes to download and start all the containers, watch the output of kubectl get pods -n sock-shop to see when they’re all up and running.

Then go to the IP address of your cluster’s master node in your browser, and specify the given port. So for example, http://<master_ip>:<port>. In the example above, this was 30001, but it may be a different port for you.

If there is a firewall, make sure it exposes this port to the internet before you try to access it.

To uninstall the socks shop, run kubectl delete namespace sock-shop on the master.

Tear down

To undo what kubeadm did, you should first drain the node and make sure that the node is empty before shutting it down.

Talking to the master with the appropriate credentials, run:

kubectl drain <node name> --delete-local-data --force --ignore-daemonsets
kubectl delete node <node name>

Then, on the node being removed, reset all kubeadm installed state:

kubeadm reset

If you wish to start over simply run kubeadm init or kubeadm join with the appropriate arguments.

Note: kubeadm reset will not delete any etcd data if external etcd is used. This means that if you run kubeadm init again using the same etcd endpoints, you will see state from previous clusters. To wipe etcd data after reset, it is recommended you use a client like etcdctl, such as:

etcdctl del "" --prefix

See their documentation for more information.

Upgrading

Instructions for upgrading kubeadm clusters are available for:

Explore other add-ons

See the list of add-ons to explore other add-ons, including tools for logging, monitoring, network policy, visualization & control of your Kubernetes cluster.

What’s next

Feedback

Version skew policy

The kubeadm CLI tool of version vX.Y may deploy clusters with a control plane of version vX.Y or vX.(Y-1). kubeadm CLI vX.Y can also upgrade an existing kubeadm-created cluster of version vX.(Y-1).

Due to that we can’t see into the future, kubeadm CLI vX.Y may or may not be able to deploy vX.(Y+1) clusters.

Example: kubeadm v1.8 can deploy both v1.7 and v1.8 clusters and upgrade v1.7 kubeadm-created clusters to v1.8.

Please also check our installation guide for more information on the version skew between kubelets and the control plane.

kubeadm is multi-platform

kubeadm deb/rpm packages and binaries are built for amd64, arm (32-bit), arm64, ppc64le, and s390x following the multi-platform proposal.

Only some of the network providers offer solutions for all platforms. Please consult the list of network providers above or the documentation from each provider to figure out whether the provider supports your chosen platform.

Limitations

Please note: kubeadm is a work in progress and these limitations will be addressed in due course.

  1. The cluster created here has a single master, with a single etcd database running on it. This means that if the master fails, your cluster loses its configuration data and will need to be recreated from scratch. Adding HA support (multiple etcd servers, multiple API servers, etc) to kubeadm is still a work-in-progress.

    Workaround: regularly back up etcd. The etcd data directory configured by kubeadm is at /var/lib/etcd on the master.

Troubleshooting

If you are running into difficulties with kubeadm, please consult our troubleshooting docs.

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