In the last post, we installed Kubernetes locally on a single RHEL7 server. This time, we’re modifying the procedure to distribute jobs over two servers. The installation steps are exactly the same, up until we start Kubernetes, so I won’t rehash… see them here: http://nicksabine.com/post/kubernetes-rhel7
Instead of starting Kubernetes via script, we’re going to start via systemd.
In my configuration, I have the following VMs:
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Create all of the following files on the master. On the minion, create only the kubernetes-kubelet.service and kubernetes-proxy.service files.
/usr/lib/systemd/system/kubernetes-apiserver.service:
[Unit] Description=Kubernetes API Server [Service] ExecStart=/opt/kubernetes/output/go/bin/apiserver --logtostderr=true -etcd_servers=http://localhost:4001 -address=0.0.0.0 -port=8080 -machines=192.168.56.102,192.168.56.103 [Install] WantedBy=multi-user.target
Note: in the above, replace the comma-delimited list of -machines with the IPs of all the minions in the cluster.
/usr/lib/systemd/system/kubernetes-controller-manager.service:
[Unit] Description=Kubernetes Controller Manager [Service] ExecStart=/opt/kubernetes/output/go/bin/controller-manager --logtostderr=true -master=192.168.56.103:8080 [Install] WantedBy=multi-user.target
Note: in the above, replace the IP of the master
/usr/lib/systemd/system/etcd.service:
[Unit] Description=Etcd Server After=network.target [Service] Type=simple #etcd logs to the journal directly, suppress double logging StandardOutput=null WorkingDirectory=/opt/etcd ExecStart=/opt/etcd/bin/etcd [Install] WantedBy=multi-user.target
/usr/lib/systemd/system/kubernetes-kubelet.service:
[Unit] Description=Kubernetes Kubelet [Service] ExecStart=/opt/kubernetes/output/go/bin/kubelet --logtostderr=true -etcd_servers=http://192.168.56.103:4001 -address=192.168.56.102 -hostname_override=192.168.56.102 [Install] WantedBy=multi-user.target
Note: in the above, replace the IP of the etcd_server (running on the master), and replace the -address and -hostname_override with the IP of the local minion server.
/usr/lib/systemd/system/kubernetes-proxy.service:
[Unit] Description=Kubernetes Proxy [Service] ExecStart=/opt/kubernetes/output/go/bin/proxy --logtostderr=true -etcd_servers=http://192.168.56.103:4001 [Install] WantedBy=multi-user.target
Note: in the above, replace the IP of the -etcd_servers (running on the master)
Start Kubernetes (on master)
systemctl daemon-reload systemctl enable etcd systemctl start etcd systemctl enable kubernetes-apiserver.service systemctl start kubernetes-apiserver.service systemctl enable kubernetes-controller-manager systemctl start kubernetes-controller-manager systemctl enable kubernetes-kubelet systemctl start kubernetes-kubelet systemctl enable kubernetes-proxy systemctl start kubernetes-proxy
Start Kubernetes (on minon)
systemctl daemon-reload systemctl enable kubernetes-kubelet systemctl start kubernetes-kubelet systemctl enable kubernetes-proxy systemctl start kubernetes-proxy
References:
- Getting Started Guide: https://github.com/GoogleCloudPlatform/kubernetes/blob/master/docs/getting-started-guides/locally.md
- Clustering Kubernetes on Fedora: http://developerblog.redhat.com/2014/07/31/getting-started-with-kubernetes-docker-on-fedora/
Show what’s running in Kubernetes (nothing yet!)
Tell the client where the server is running
sed -i -e 's/^KUBERNETES_PROVIDER.*$/KUBERNETES_PROVIDER="local"/' /opt/kubernetes/cluster/kube-env.sh
Note: If you want to run kubecfg.sh on any host other than the master, you need to set the master’s location in /opt/kubernetes/cluster/local/config-default.sh:
#IP LOCATIONS FOR INTERACTING WITH THE MASTER
export KUBE_MASTER_IP="192.168.56.103"
export KUBERNETES_MASTER="http://${KUBE_MASTER_IP}:8080"
List pods:
/opt/kubernetes/cluster/kubecfg.sh list /pods
List services:
/opt/kubernetes/cluster/kubecfg.sh list /services
List Replication Controllers:
/opt/kubernetes/cluster/kubecfg.sh list /replicationControllers
Once you have this up and running, try deploying the GuestBook example: https://github.com/GoogleCloudPlatform/kubernetes/tree/master/examples/guestbook, but note that Kubernetes will not be able to deploy more than one of each type of pod per minion due to port conflicts. So if you are running a 2-minion cluster, the replicationController for the frontend needs to be modified to create 2 replicas, rather than 3.