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Ansible Role: k3s

Ansible role for installing Rancher Labs k3s ("Lightweight Kubernetes") as either a standalone server or cluster.

Build Status

Requirements

The control host requires the following Python dependencies:

  • jmespath >= 0.9.0

This role has been tested on Ansible 2.7.0+ against the following Linux Distributions:

  • Amazon Linux 2
  • CentOS 8
  • CentOS 7
  • Debian 9
  • Debian 10
  • Fedora 29
  • Fedora 30
  • Fedora 31
  • openSUSE Leap 15
  • Ubuntu 18.04 LTS

Disclaimer

⚠️ May not be suitable for production use!

Rancher Labs is awesome and has released k3s as v1.0.0, however at the time of creating this role I do not have a k3s cluster in production nor am I unlikely to ever have one. Please ensure you practice extreme caution and operational rigor before using this role for any serious workloads.

If you have any problems please create a GitHub issue, I maintain this role in my spare time so I cannot promise a speedy fix delivery.

Role Variables

Group Variables

Below are variables that are set against all of the play hosts for environment consistency.

Variable Description Default Value
k3s_cluster_state State of cluster: installed, started, stopped, restarted, downloaded, uninstalled. installed
k3s_release_version Use a specific version of k3s, eg. v0.2.0. Specify false for latest. false
k3s_github_url Set the GitHub URL to install k3s from. https://github.com/rancher/k3s
k3s_install_dir Installation directory for k3s. /usr/local/bin
k3s_server_manifests_dir Path for place the k3s_server_manifests_templates. /var/lib/rancher/k3s/server/manifests
k3s_server_manifests_templates A list of Auto-Deploying Manifests Templates. []
k3s_use_experimental Allow the use of experimental features in k3s. false
k3s_non_root Install k3s as non-root user. See notes below. false
k3s_control_workers Are control hosts also workers? true
k3s_cluster_cidr Network CIDR to use for pod IPs 10.42.0.0/16
k3s_service_cidr Network CIDR to use for service IPs 10.43.0.0/16
k3s_control_node_address Use a specific control node address. IP or FQDN. NULL
k3s_control_token Use a specific control token, please read notes below. NULL
k3s_https_port HTTPS port listening port. 6443
k3s_use_docker Use Docker rather than Containerd? false
k3s_no_flannel Do not use Flannel false
k3s_flannel_backend Flannel backend ('none', 'vxlan', 'ipsec', 'host-gw' or 'wireguard') vxlan
k3s_no_coredns Do not use CoreDNS false
k3s_cluster_dns Cluster IP for CoreDNS service. Should be in your service-cidr range. NULL
k3s_cluster_domain Cluster Domain. cluster.local
k3s_resolv_conf Kubelet resolv.conf file NULL
k3s_no_traefik Do not use Traefik false
k3s_no_servicelb Do not use ServiceLB, necessary for using something like MetalLB. false
k3s_no_local_storage Do not use Local Storage false
k3s_default_local_storage_path Set Local Storage Path. Specify false for default. false
k3s_no_metrics_server Do not deploy metrics server false
k3s_disable_scheduler Disable Kubernetes default scheduler false
k3s_disable_cloud_controller Disable k3s default cloud controller manager. false
k3s_disable_network_policy Disable k3s default network policy controller. false
k3s_write_kubeconfig_mode Define the file mode from the generated KubeConfig, eg. 644 NULL
k3s_datastore_endpoint Define the database or etcd cluster endpoint for HA. NULL
k3s_datastore_cafile Define the database TLS CA file. NULL
k3s_datastore_certfile Define the database TLS Cert file. NULL
k3s_datastore_keyfile Define the database TLS Key file. NULL
k3s_become_for_all Enable become for all (where value for k3s_become_for_* is NULL false
k3s_become_for_systemd Enable become for systemd NULL
k3s_become_for_install_dir Enable become for writing to k3s_install_dir NULL
k3s_become_for_usr_local_bin Enable become for writing to /usr/local/bin/ NULL
k3s_dqlite_datastore Use DQLite as the database backend for HA. (EXPERIMENTAL) false
k3s_secrets_encryption Use secrets encryption at rest. (EXPERIMENTAL) false

Important note about k3s_release_version

If you do not set a k3s_release_version the latest version of k3s will be installed. If you are developing against a specific version of k3s you must ensure this is set in your Ansible configuration, eg:

k3s_release_version: v0.2.0

Important note about k3s_non_root

To install k3s as non root you must not use become: true. The intention of this variable is to run a single node development environment. At the time of release v1.0.1, rootless is still experimental.

You must also ensure that you set k3s_use_experimental to true.

Additionally k3s_install_dir must be writable by your user.

Important notes about k3s_control_node_address and k3s_control_token

If you set this, you are explicitly specifying the control host that agents should connect to, the value should be an IP address or FQDN.

If the control host is not configured by this role, then you need to also specify the k3s_control_token.

Please note that this may potentially break setting up agents.

Host Variables

Below are variables that are set against specific hosts in your inventory.

Variable Description Default Value
k3s_control_node Define the host as a control plane node, (True/False). false
k3s_node_name Define the name of this node. $(hostname)
k3s_node_id Define the ID of this node. NULL
k3s_flannel_interface Define the flannel proxy interface for this node. NULL
k3s_bind_address Define the bind address for this node. localhost
k3s_node_ip_address IP Address to advertise for this node. NULL
k3s_node_external_address External IP Address to advertise for this node. NULL
k3s_node_labels List of node labels. NULL
k3s_kubelet_args A list of kubelet args to pass to the server. []
k3s_node_taints List of node taints. NULL
k3s_node_data_dir Folder to hold state. /var/lib/rancher/k3s
k3s_tls_san Add additional hosname or IP as Subject Alternate Name in the TLS cert. NULL

Important note about k3s_control_node and High Availability (HA)

By default only one host will be defined as a control node by Ansible, If you do not set a host as a control node, the role will automatically delegate the first play host as a control node (master). This is not suitable for use in a Production workload.

If multiple hosts have k3s_control_node set to true, you must also set k3s_datastore_endpoint as the connection string to a MySQL or PostgreSQL database, or etcd cluster else the play will fail.

If using TLS, the CA, Certificate and Key need to already be available on the play hosts.

See: High Availability with an External DB

Since K3s v1.0.0 it is possible to use DQLite as the backend database, and this is done by setting k3s_dqlite_datastore to true. As this is an experimental feature you will also need to set k3s_use_experimental to true.

Important note about k3s_flannel_interface

If you are running k3s on systems with multiple network interfaces, it is necessary to have the flannel interface on a network interface that is routable to the master node(s).

Notes about k3s_kubelet_args

This parameter allows for assigning additional kubelet args to the server during runtime. For instance, to use the Azure Cloud Controller, assign the following to the master node's configuration in your host file.

Note, when using an external cloud controller as below, ensure that the native k3s cloud controller is disabled by setting the k3s_disable_cloud_controller to true.

YAML:

k3s_kubelet_args:
  - cloud-provider: external
  - provider-id: azure

Notes about k3s_node_labels and k3s_node_taints

Both these variables are lists that will be iterated on. The below example will output the following:

YAML:

k3s_node_labels:
  - foo: bar
  - hello: world

k3s_node_taints:
  - key1: value1:NoExecute

ARGS:

--node-label foo=bar \
--node-label hello=world \
--node-taint key1=value1:NoExecute

Dependencies

No dependencies on other roles.

Example Playbooks

Example playbook, single master node running v0.10.2:

- hosts: k3s_nodes
  become: true
  roles:
     - { role: xanmanning.k3s, k3s_release_version: v0.10.2 }

Example playbook, Highly Available running the latest release:

- hosts: k3s_nodes
  become: true
  vars:
    molecule_is_test: true
    k3s_control_node_address: loadbalancer
    k3s_datastore_endpoint: "postgres://postgres:verybadpass@database:5432/postgres?sslmode=disable"
  pre_tasks:
    - name: Set each node to be a control node
      set_fact:
        k3s_control_node: true
      when: inventory_hostname in ['node2', 'node3']
  roles:
    - role: xanmanning.k3s

License

BSD 3-clause

Author Information

Xan Manning