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