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Kubernetes Ansible

This playbook and set of roles set up a Kubernetes cluster onto machines. They can be real hardware, VMs, things in a public cloud, etc. Anything that you can connect to via SSH.

Before starting

  • Record the IP address/hostname of which machine you want to be your master (only support a single master)
  • Record the IP address/hostname of the machine you want to be your etcd server (often same as master, only one)
  • Record the IP addresses/hostname of the machines you want to be your nodes. (the master can also be a node)
  • Make sure your ansible running machine has ansible 1.9 and python-netaddr installed.

Setup

Configure inventory

Add the system information gathered above into a file called inventory, or create a new one for the cluster. Place the inventory file into the ./inventory directory.

For example:

[masters]
kube-master-test.example.com

[etcd:children]
masters

[nodes]
kube-minion-test-[1:2].example.com

Configure Cluster options

Look through all of the options in inventory/group_vars/all.yml and set the variables to reflect your needs. The options are described there in full detail.

Securing etcd

If you wish to use TLS certificates for your etcd cluster you have to specify TLS keypairs and https for etcd_url_scheme/etcd_peer_url_scheme. This will enable encrypted communication, but will not authenticate the clients certificate validity. To prevent unauthorized access to your etcd cluster, please set etcd_client_cert_auth/etcd_peer_client_cert_auth correspondingly to true.

Running the playbook

After going through the setup, run the deploy-cluster.sh script from within the scripts directory:

$ cd scripts/ && ./deploy-cluster.sh

You may override the inventory file by running:

INVENTORY=myinventory ./deploy-cluster.sh

The directory containing myinventory file must contain the default inventory/group_vars directory as well (or its equivalent). Otherwise variables defined in group_vars/all.yml will not be set.

In general this will work on very recent Fedora, rawhide or F21. Future work to support RHEL7, CentOS, and possible other distros should be forthcoming.

Targeted runs

You can just setup certain parts instead of doing it all.

Etcd

$ ./deploy-cluster.sh --tags=etcd

Kubernetes master

$ ./deploy-cluster.sh --tags=masters

Kubernetes nodes

$ ./deploy-cluster.sh --tags=nodes

Addons

By default, the Ansible playbook deploys Kubernetes addons as well. Addons consist of:

  • DNS (skydns)
  • cluster monitoring (Grafana, Heapster, InfluxDB)
  • cluster logging (Kibana, ElasticSearch)
  • Kubernetes dashboard
  • Kubernetes dash

In order to skip addons deployment, run

$ ./deploy-cluster.sh --skip-tags=addons

In order to run addons deployment only (requires kubernetes master already deployed), run

$ ./deploy-cluster.sh --tags=addons or $ ./deploy-addons.sh

Component sources

Each component can be installed from various sources. For instance:

  • distribution packages
  • github release
  • kubernetes built from local source codes

By default, every component (etcd, docker, kubernetes, etc.) is installed via distribution package manager. Currently, the following component types are supported:

  • etcd_source_type: for etcd role
  • flannel_source_type: for flannel role
  • kube_source_type: for master and node roles
  • source_type: for other roles (and components)

To see a full list of available types, see corresponding role's default variables.

Kubernetes source type

Available types (see kube_source_type under roles/kubernetes/defaults/main.yml):

  • packageManager
  • localBuild
  • github-release
  • distribution-rpm

In case of a package manager, the kube-apiserver binary is shipped with cap_net_bind_service=ep capability set. The capability allows the apiserver to listen on 443 port. In a case of localBuild and github-release, the capability is not set. In order for apiserver to listen on a secure port, change the port (see kube_master_api_port under roles/kubernetes/defaults/main.yml). For instance to listen on 6443.

In order to apply the distribution-rpm type, location of an rpm must be specified. See kube_rpm_url_base and kube_rpm_url_sufix variables under roles/kubernetes/defaults/main.yml.

Network Service

By changing the networking variable in the inventory/group_vars/all.yml file, you can choose the network-service to use. The default is flannel.

$ ./deploy-cluster.sh --tags=network-service-install

Troubleshooting

  • When updating flannel to version 0.5.5-7 or higher on Fedora, the /etc/sysconfig/flannel configuration file (if changed) must be updated to reflect renamed systemd environment variables.

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