--- assignees: - lavalamp - thockin --- * TOC {:toc} ## Prerequisites To configure Kubernetes with CentOS, you'll need a machine to act as a master, and one or more CentOS 7 hosts to act as cluster nodes. ## Starting a cluster This is a getting started guide for CentOS. It is a manual configuration so you understand all the underlying packages / services / ports, etc... The Kubernetes package provides a few services: kube-apiserver, kube-scheduler, kube-controller-manager, kubelet, kube-proxy. These services are managed by systemd and the configuration resides in a central location: /etc/kubernetes. We will break the services up between the hosts. The first host, centos-master, will be the Kubernetes master. This host will run the kube-apiserver, kube-controller-manager and kube-scheduler. In addition, the master will also run _etcd_. The remaining hosts, centos-minion-n will be the nodes and run kubelet, proxy, cadvisor and docker. All of then run flanneld as networking overlay. **System Information:** Hosts: Please replace host IP with your environment. ```conf centos-master = 192.168.121.9 centos-minion-1 = 192.168.121.65 centos-minion-2 = 192.168.121.66 centos-minion-3 = 192.168.121.67 ``` **Prepare the hosts:** * Create a /etc/yum.repos.d/virt7-docker-common-release.repo on all hosts - centos-{master,minion-n} with following information. ```conf [virt7-docker-common-release] name=virt7-docker-common-release baseurl=http://cbs.centos.org/repos/virt7-docker-common-release/x86_64/os/ gpgcheck=0 ``` * Install Kubernetes, etcd and flannel on all hosts - centos-{master,minion-n}. This will also pull in docker and cadvisor. ```shell yum -y install --enablerepo=virt7-docker-common-release kubernetes etcd flannel ``` * Add master and node to /etc/hosts on all machines (not needed if hostnames already in DNS) ```shell echo "192.168.121.9 centos-master 192.168.121.65 centos-minion-1 192.168.121.66 centos-minion-2 192.168.121.67 centos-minion-3" >> /etc/hosts ``` * Edit /etc/kubernetes/config which will be the same on all hosts to contain: ```shell # Comma separated list of nodes in the etcd cluster KUBE_ETCD_SERVERS="--etcd-servers=http://centos-master:2379" # logging to stderr means we get it in the systemd journal KUBE_LOGTOSTDERR="--logtostderr=true" # journal message level, 0 is debug KUBE_LOG_LEVEL="--v=0" # Should this cluster be allowed to run privileged docker containers KUBE_ALLOW_PRIV="--allow-privileged=false" # How the replication controller and scheduler find the kube-apiserver KUBE_MASTER="--master=http://centos-master:8080" ``` * Disable the firewall on the master and all the nodes, as docker does not play well with other firewall rule managers ```shell systemctl disable iptables-services firewalld systemctl stop iptables-services firewalld ``` **Configure the Kubernetes services on the master.** * Edit /etc/etcd/etcd.conf to appear as such: ```shell # [member] ETCD_NAME=default ETCD_DATA_DIR="/var/lib/etcd/default.etcd" ETCD_LISTEN_CLIENT_URLS="http://0.0.0.0:2379" #[cluster] ETCD_ADVERTISE_CLIENT_URLS="http://0.0.0.0:2379" ``` * Edit /etc/kubernetes/apiserver to appear as such: ```shell # The address on the local server to listen to. KUBE_API_ADDRESS="--address=0.0.0.0" # The port on the local server to listen on. KUBE_API_PORT="--port=8080" # Port kubelets listen on KUBELET_PORT="--kubelet-port=10250" # Address range to use for services KUBE_SERVICE_ADDRESSES="--service-cluster-ip-range=10.254.0.0/16" # Add your own! KUBE_API_ARGS="" ``` * Configure ETCD to hold the network overlay configuration on master: **Warning** This network must be unused in your network infrastructure! `172.30.0.0/16` is free in our network. ```shell $ etcdctl mkdir /kube-centos/network $ etcdctl mk /kube-centos/network/config "{ \"Network\": \"172.30.0.0/16\", \"SubnetLen\": 24, \"Backend\": { \"Type\": \"vxlan\" } }" ``` * Configure flannel to overlay Docker network in /etc/sysconfig/flanneld on the master (also in the nodes as we'll see): ```shell # etcd url location. Point this to the server where etcd runs FLANNEL_ETCD="http://centos-master:2379" # etcd config key. This is the configuration key that flannel queries # For address range assignment FLANNEL_ETCD_KEY="/kube-centos/network" # Any additional options that you want to pass FLANNEL_OPTIONS="" ``` * Start the appropriate services on master: ```shell for SERVICES in etcd kube-apiserver kube-controller-manager kube-scheduler flanneld; do systemctl restart $SERVICES systemctl enable $SERVICES systemctl status $SERVICES done ``` **Configure the Kubernetes services on the nodes.** ***We need to configure the kubelet and start the kubelet and proxy*** * Edit /etc/kubernetes/kubelet to appear as such: ```shell # The address for the info server to serve on KUBELET_ADDRESS="--address=0.0.0.0" # The port for the info server to serve on KUBELET_PORT="--port=10250" # You may leave this blank to use the actual hostname KUBELET_HOSTNAME="--hostname-override=centos-minion-n" # Check the node number! # Location of the api-server KUBELET_API_SERVER="--api-servers=http://centos-master:8080" # Add your own! KUBELET_ARGS="" ``` * Configure flannel to overlay Docker network in /etc/sysconfig/flanneld (in all the nodes) ```shell # etcd url location. Point this to the server where etcd runs FLANNEL_ETCD="http://centos-master:2379" # etcd config key. This is the configuration key that flannel queries # For address range assignment FLANNEL_ETCD_KEY="/kube-centos/network" # Any additional options that you want to pass FLANNEL_OPTIONS="" ``` * Start the appropriate services on node (centos-minion-n). ```shell for SERVICES in kube-proxy kubelet flanneld docker; do systemctl restart $SERVICES systemctl enable $SERVICES systemctl status $SERVICES done ``` * Configure kubectl ```shell kubectl config set-cluster default-cluster --server=http://centos-master:8080 kubectl config set-context default-context --cluster=default-cluster --user=default-admin kubectl config use-context default-context ``` *You should be finished!* * Check to make sure the cluster can see the node (on centos-master) ```shell $ kubectl get nodes NAME LABELS STATUS centos-minion-1 Ready centos-minion-2 Ready centos-minion-3 Ready ``` **The cluster should be running! Launch a test pod.** You should have a functional cluster, check out [101](/docs/user-guide/walkthrough/)! ## Support Level IaaS Provider | Config. Mgmt | OS | Networking | Docs | Conforms | Support Level -------------------- | ------------ | ------ | ---------- | --------------------------------------------- | ---------| ---------------------------- Bare-metal | custom | CentOS | flannel | [docs](/docs/getting-started-guides/centos/centos_manual_config) | | Community ([@coolsvap](https://github.com/coolsvap)) For support level information on all solutions, see the [Table of solutions](/docs/getting-started-guides/#table-of-solutions) chart.