kubernetes master #0

Supports: xenial bionic
Add to new model


Kubernetes is an open-source platform for deploying, scaling, and operations of application containers across a cluster of hosts. Kubernetes is portable in that it works with public, private, and hybrid clouds. Extensible through a pluggable infrastructure. Self healing in that it will automatically restart and place containers on healthy nodes if a node ever goes away.


Kubernetes is an open source system for managing application containers across a cluster of hosts. The Kubernetes project was started by Google in 2014, combining the experience of running production workloads combined with best practices from the community.

The Kubernetes project defines some new terms that may be unfamiliar to users or operators. For more information please refer to the concept guide in the getting started guide.

This charm is an encapsulation of the Kubernetes master processes and the operations to run on any cloud for the entire lifecycle of the cluster.

This charm is built from other charm layers using the Juju reactive framework. The other layers focus on specific subset of operations making this layer specific to operations of Kubernetes master processes.


This charm is not fully functional when deployed by itself. It requires other charms to model a complete Kubernetes cluster. A Kubernetes cluster needs a distributed key value store such as Etcd and the kubernetes-worker charm which delivers the Kubernetes node services. A cluster requires a Software Defined Network (SDN), a Container Runtime such as containerd, and Transport Layer Security (TLS) so the components in a cluster communicate securely.

Please take a look at the Canonical Distribution of Kubernetes or the Kubernetes core bundles for examples of complete models of Kubernetes clusters.


The kubernetes-master charm takes advantage of the Juju Resources feature to deliver the Kubernetes software.

In deployments on public clouds the Charm Store provides the resource to the charm automatically with no user intervention. Some environments with strict firewall rules may not be able to contact the Charm Store. In these network restricted environments the resource can be uploaded to the model by the Juju operator.

Snap Refresh

The kubernetes resources used by this charm are snap packages. When not specified during deployment, these resources come from the public store. By default, the snapd daemon will refresh all snaps installed from the store four (4) times per day. A charm configuration option is provided for operators to control this refresh frequency.

NOTE: this is a global configuration option and will affect the refresh time for all snaps installed on a system.


## refresh kubernetes-master snaps every tuesday
juju config kubernetes-master snapd_refresh="tue"

## refresh snaps at 11pm on the last (5th) friday of the month
juju config kubernetes-master snapd_refresh="fri5,23:00"

## delay the refresh as long as possible
juju config kubernetes-master snapd_refresh="max"

## use the system default refresh timer
juju config kubernetes-master snapd_refresh=""

For more information on the possible values for snapd_refresh, see the refresh.timer section in the system options documentation.


This charm supports some configuration options to set up a Kubernetes cluster that works in your environment:


Comma separated authorization modes. For example, enable RBAC and Node authorization:

juju config kubernetes-master authorization-mode="RBAC,Node"


The domain name to use for the Kubernetes cluster for DNS.


Enables the installation of Kubernetes dashboard, Heapster, Grafana, and InfluxDB.

DNS for the cluster

The DNS add-on allows the pods to have a DNS names in addition to IP addresses. The Kubernetes cluster DNS server (based off the SkyDNS library) supports forward lookups (A records), service lookups (SRV records) and reverse IP address lookups (PTR records). More information about the DNS can be obtained from the Kubernetes DNS admin guide.


The kubernetes-master charm models a few one time operations called Juju actions that can be run by Juju users.


This action creates RADOS Block Device (RBD) in Ceph and defines a Persistent Volume in Kubernetes so the containers can use durable storage. This action requires a relation to the ceph-mon charm before it can create the volume.


This action restarts the master processes kube-apiserver, kube-controller-manager, and kube-scheduler when the user needs a restart.

More information


The kubernetes-master charm is free and open source operations created by the containers team at Canonical.

Canonical also offers enterprise support and customization services. Please refer to the Kubernetes product page for more details.


(string) Specify the docker registry to use when applying addons. DEPRECATED in 1.15: Use the broader 'image-registry' config option instead. If both options are set, 'addons-registry' will be used to configure the cdk-addons snap until v1.17 is released. After that, the 'addons-registry' option will have no effect.
(string) Allow kube-apiserver to run in privileged mode. Supported values are "true", "false", and "auto". If "true", kube-apiserver will run in privileged mode by default. If "false", kube-apiserver will never run in privileged mode. If "auto", kube-apiserver will not run in privileged mode by default, but will switch to privileged mode if gpu hardware is detected on a worker node.
(string) Space separated list of flags and key=value pairs that will be passed as arguments to kube-apiserver. For example a value like this: runtime-config=batch/v2alpha1=true profiling=true will result in kube-apiserver being run with the following options: --runtime-config=batch/v2alpha1=true --profiling=true
(string) Audit policy passed to kube-apiserver via --audit-policy-file. For more info, please refer to the upstream documentation at https://kubernetes.io/docs/tasks/debug-application-cluster/audit/
apiVersion: audit.k8s.io/v1beta1 kind: Policy rules: # Don't log read-only requests from the apiserver - level: None users: ["system:apiserver"] verbs: ["get", "list", "watch"] # Don't log kube-proxy watches - level: None users: ["system:kube-proxy"] verbs: ["watch"] resources: - resources: ["endpoints", "services"] # Don't log nodes getting their own status - level: None userGroups: ["system:nodes"] verbs: ["get"] resources: - resources: ["nodes"] # Don't log kube-controller-manager and kube-scheduler getting endpoints - level: None users: ["system:unsecured"] namespaces: ["kube-system"] verbs: ["get"] resources: - resources: ["endpoints"] # Log everything else at the Request level. - level: Request omitStages: - RequestReceived
(string) Audit webhook config passed to kube-apiserver via --audit-webhook-config-file. For more info, please refer to the upstream documentation at https://kubernetes.io/docs/tasks/debug-application-cluster/audit/
(string) Comma separated authorization modes. Allowed values are "RBAC", "Node", "Webhook", "ABAC", "AlwaysDeny" and "AlwaysAllow".
(string) Snap channel to install Kubernetes master services from
(string) Password to be used for admin user (leave empty for random password).
(string) Space separated list of flags and key=value pairs that will be passed as arguments to kube-controller-manager. For example a value like this: runtime-config=batch/v2alpha1=true profiling=true will result in kube-controller-manager being run with the following options: --runtime-config=batch/v2alpha1=true --profiling=true
(string) Method of authentication for the Kubernetes dashboard. Allowed values are "auto", "basic", and "token". If set to "auto", basic auth is used unless Keystone is related to kubernetes-master, in which case token auth is used.
(string) The storage class to make the default storage class. Allowed values are "auto", "none", "ceph-xfs", "ceph-ext4". Note: Only works in Kubernetes >= 1.10
(string) DNS provider addon to use. Can be "auto", "core-dns", "kube-dns", or "none". CoreDNS is only supported on Kubernetes 1.14+. When set to "auto", the behavior is as follows: - New deployments of Kubernetes 1.14+ will use CoreDNS - New deployments of Kubernetes 1.13 or older will use KubeDNS - Upgraded deployments will continue to use whichever provider was previously used.
(string) The local domain for cluster dns
(boolean) Deploy the Kubernetes Dashboard and Heapster addons
(boolean) If true and the Keystone charm is related, users will authorize against the Keystone server. Note that if related, users will always authenticate against Keystone.
(boolean) If true the metrics server for Kubernetes will be deployed onto the cluster.
(string) Load the nvidia device plugin daemonset. Supported values are "auto" and "false". When "auto", the daemonset will be loaded only if GPUs are detected. When "false" the nvidia device plugin will not be loaded.
(string) Space separated list of extra deb packages to install.
(string) Space-separated list of extra SAN entries to add to the x509 certificate created for the master nodes.
(string) DNS entry to use with the HA Cluster subordinate charm. Mutually exclusive with ha-cluster-vip.
(string) Virtual IP for the charm to use with the HA Cluster subordinate charm Mutually exclusive with ha-cluster-dns. Multiple virtual IPs are separated by spaces.
(string) Container image registry to use for CDK. This includes addons like the Kubernetes dashboard, metrics server, ingress, and dns along with non-addon images including the pause container and default backend image.
(string) List of signing keys for install_sources package sources, per charmhelpers standard format (a yaml list of strings encoded as a string). The keys should be the full ASCII armoured GPG public keys. While GPG key ids are also supported and looked up on a keyserver, operators should be aware that this mechanism is insecure. null can be used if a standard package signing key is used that will already be installed on the machine, and for PPA sources where the package signing key is securely retrieved from Launchpad.
(string) List of extra apt sources, per charm-helpers standard format (a yaml list of strings encoded as a string). Each source may be either a line that can be added directly to sources.list(5), or in the form ppa:<user>/<ppa-name> for adding Personal Package Archives, or a distribution component to enable.
(string) Policy for Keystone authentication. This is used when a Keystone charm is related to kubernetes-master in order to provide authentication and authorization for Keystone users on the Kubernetes cluster.
apiVersion: v1 kind: ConfigMap metadata: name: k8s-auth-policy namespace: kube-system labels: k8s-app: k8s-keystone-auth data: policies: | [ { "resource": { "verbs": ["get", "list", "watch"], "resources": ["*"], "version": "*", "namespace": "*" }, "match": [ { "type": "role", "values": ["k8s-viewers"] }, { "type": "project", "values": ["k8s"] } ] }, { "resource": { "verbs": ["*"], "resources": ["*"], "version": "*", "namespace": "default" }, "match": [ { "type": "role", "values": ["k8s-users"] }, { "type": "project", "values": ["k8s"] } ] }, { "resource": { "verbs": ["*"], "resources": ["*"], "version": "*", "namespace": "*" }, "match": [ { "type": "role", "values": ["k8s-admins"] }, { "type": "project", "values": ["k8s"] } ] } ]
(string) Keystone certificate authority encoded in base64 for securing communications to Keystone. For example: `juju config kubernetes-master keystone-ssl-ca=$(base64 /path/to/ca.crt)`
(string) Space separated list of IP addresses of loadbalancers in front of the control plane. These can be either virtual IP addresses that have been floated in front of the control plane or the IP of a loadbalancer appliance such as an F5. Workers will alternate IP addresses from this list to distribute load - for example If you have 2 IPs and 4 workers, each IP will be used by 2 workers. Note that this will only work if kubeapi-load-balancer is not in use and there is a relation between kubernetes-master:kube-api-endpoint and kubernetes-worker:kube-api-endpoint. If using the kubeapi-load-balancer, see the loadbalancer-ips configuration variable on the kubeapi-load-balancer charm.
(string) Configuration to set up volume for influxdb/grafana. e.g influxdb: hostPath: path: /influxdb type: Directory grafana: hostPath: path: /grafana type: Directory
influxdb: emptyDir: {} grafana: emptyDir: {}
(string) Used by the nrpe subordinate charms. A string that will be prepended to instance name to set the host name in nagios. So for instance the hostname would be something like: juju-myservice-0 If you're running multiple environments with the same services in them this allows you to differentiate between them.
(string) A comma-separated list of nagios servicegroups. If left empty, the nagios_context will be used as the servicegroup
(string) The status of service-affecting packages will be set to this value in the dpkg database. Valid values are "install" and "hold".
(string) Space separated list of flags and key=value pairs that will be passed as arguments to kube-proxy. For example a value like this: runtime-config=batch/v2alpha1=true profiling=true will result in kube-apiserver being run with the following options: --runtime-config=batch/v2alpha1=true --profiling=true
(boolean) When true, master nodes will not be upgraded until the user triggers it manually by running the upgrade action.
(string) Space separated list of flags and key=value pairs that will be passed as arguments to kube-scheduler. For example a value like this: runtime-config=batch/v2alpha1=true profiling=true will result in kube-scheduler being run with the following options: --runtime-config=batch/v2alpha1=true --profiling=true
(string) CIDR to user for Kubernetes services. Cannot be changed after deployment.
(string) DEPRECATED. Use snap-http-proxy and snap-https-proxy model configuration settings. HTTP/HTTPS web proxy for Snappy to use when accessing the snap store.
(string) DEPRECATED. Use snap-store-proxy model configuration setting. The address of a Snap Store Proxy to use for snaps e.g. http://snap-proxy.example.com
(string) How often snapd handles updates for installed snaps. Setting an empty string will check 4x per day. Set to "max" to delay the refresh as long as possible. You may also set a custom string as described in the 'refresh.timer' section here: https://forum.snapcraft.io/t/system-options/87
(string) The storage backend for kube-apiserver persistence. Can be "etcd2", "etcd3", or "auto". Auto mode will select etcd3 on new installations, or etcd2 on upgrades.
(string) YAML formatted associative array of sysctl values, e.g.: '{kernel.pid_max : 4194303 }'. Note that kube-proxy handles the conntrack settings. The proper way to alter them is to use the proxy-extra-args config to set them, e.g.: juju config kubernetes-master proxy-extra-args="conntrack-min=1000000 conntrack-max-per-core=250000" juju config kubernetes-worker proxy-extra-args="conntrack-min=1000000 conntrack-max-per-core=250000" The proxy-extra-args conntrack-min and conntrack-max-per-core can be set to 0 to ignore kube-proxy's settings and use the sysctl settings instead. Note the fundamental difference between the setting of conntrack-max-per-core vs nf_conntrack_max.
{ net.ipv4.conf.all.forwarding : 1, net.ipv4.neigh.default.gc_thresh1 : 128, net.ipv4.neigh.default.gc_thresh2 : 28672, net.ipv4.neigh.default.gc_thresh3 : 32768, net.ipv6.neigh.default.gc_thresh1 : 128, net.ipv6.neigh.default.gc_thresh2 : 28672, net.ipv6.neigh.default.gc_thresh3 : 32768, fs.inotify.max_user_instances : 8192, fs.inotify.max_user_watches: 1048576 }