How to use MicroK8s with Juju
Juju works well with MicroK8s to provide a full CNCF-certified Kubernetes system in under 60 seconds.
Contents:
- Install and set up MicroK8s
- Install the Juju client
- Create a controller
- Add a model
- Deploy a Kubernetes charm
- Remove configuration and software
- Next steps
Install and set up MicroK8s
For installation instructions for other platforms, including Windows 10, macOS, ARM devices such as Raspberry Pi and LXD, see the MicroK8s documentation.
The easiest way to install MicroK8s is via snap:
sudo snap install microk8s --classic
Join the microk8s group
When strictly confined MicroK8s is released, the group you need to be a member of changes to snap_microk8s .
Add your account to the microk8s group. This grants the account elevated privileges to the cluster, meaning that sudo will not be required to interact with microk8s:
sudo usermod -a -G microk8s $USER
sudo chown -f -R $USER ~/.kube
This command requires you to log out and log back in before the changes are applied.
su - $USER
Alternatively, exit the shell by executing exit or by using Ctrl + D and restart your session.
Await installation
MicroK8s will take a few minutes to install all of its components.
microk8s status --wait-ready
Verify installation
Now let’s inspect the cluster with the microk8s.kubectl command:
microk8s.kubectl get all --all-namespaces
You should see output similar to:
NAMESPACE NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
default service/kubernetes ClusterIP 10.152.183.1 <none> 443/TCP 22s
It’s possible that you encounter an error message relating to permissions. If this happens, execute sudo usermod -a -G microk8s $USER and restart.
Insufficient permissions to access MicroK8s.
You can either try again with sudo or add the user ubuntu to the 'microk8s' group:
sudo usermod -a -G microk8s $USER
The new group will be available on the user's next login.
Enable DNS and storage add-ons
Now enable some MicroK8s addons for storage and DNS support:
microk8s.enable hostpath-storage dns
This will bring about changes to the cluster. Re-invoking the microk8s.kubectl get all --all-namespaces should eventually give you something like this:
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system pod/hostpath-provisioner-6d744c4f7c-t9hgh 1/1 Running 0 2m50s
kube-system pod/kube-dns-6bfbdd666c-rxnp9 3/3 Running 0 2m56s
NAMESPACE NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
default service/kubernetes ClusterIP 10.152.183.1 <none> 443/TCP 3m55s
kube-system service/kube-dns ClusterIP 10.152.183.10 <none> 53/UDP,53/TCP 2m56s
NAMESPACE NAME READY UP-TO-DATE AVAILABLE AGE
kube-system deployment.apps/hostpath-provisioner 1/1 1 1 2m50s
kube-system deployment.apps/kube-dns 1/1 1 1 2m56s
NAMESPACE NAME DESIRED CURRENT READY AGE
kube-system replicaset.apps/hostpath-provisioner-6d744c4f7c 1 1 1 2m50s
kube-system replicaset.apps/kube-dns-6bfbdd666c 1 1 1 2m56s
Install the Juju client
Just like MicroK8s, the Juju client is easiest to install via snap:
sudo snap install juju --classic
For other installation methods, see https://juju.is/docs/olm/installing-juju.
Create a controller
Juju recognises when MicroK8s is installed and automatically sets up a cloud called “microk8s”. There is no need to manually add the cluster to Juju (verify this with juju clouds --local). A controller can then be created just like a normal cloud. Here we’ve called it “micro”:
juju bootstrap microk8s micro
Important term - cloud: Within the Juju community, the term cloud has a specific meaning. A cloud is a target that Juju knows how to manage workloads for. Kubernetes clusters, including MicroK8s, are often referred to as “k8s clouds”.
Using a version of Juju earlier than v2.6.0:
Earlier versions of Juju did not have built-in support for MicroK8s. You should upgrade your version of Juju to the current stable release. If that’s not possible, you can use juju add-k8s to register your MicroK8s cluster with Juju.
Verify the bootstrap process
Confirm the microk8s cloud is live by running juju clouds. It should be visible within the controller and client sections:
juju clouds
…which should result in output similar to:
Only clouds with registered credentials are shown.
There are more clouds, use --all to see them.
Clouds available on the controller:
Cloud Regions Default Type
microk8s 1 localhost k8s
Clouds available on the client:
Cloud Regions Default Type Credentials Source Description
[...]
microk8s 1 localhost k8s 1 built-in A Kubernetes Cluster
[...]
Important concept - clouds:
A cloud, as a Juju term, means a deployment target. It includes API endpoints and credential information.
In Juju, you interact with the client (the juju command on your local machine). It connects to a controller. The controller is hosted on a cloud and controls models.
A cloud can be registered on the controller, the client or both. Registering a cloud with the client allows the client to bootstrap a new controller onto it. Registering a cloud with a controller allows it to control models hosted on multiple providers.
Add a model
A model is a wrapper for a set of related applications and infrastructure. That model represents resources needed for the applications within it, including compute, storage, and network.
juju add-model testing
Difference from traditional clouds: There is no ‘default’ model provided on k8s clouds. Creating a model implies creating a Kubernetes namespace. Rather than pollute your cluster’s namespaces, Juju favours an explicit approach.
Verify that the model has been added
Use the juju models command to list models hosted on the cloud:
juju models
The output will list the available models, their type, status, and connection details for the current client.
Controller: micro
Model Cloud/Region Type Status Access Last connection
controller microk8s/localhost kubernetes available admin just now
testing* microk8s kubernetes available admin never connected
Deploy a Kubernetes charm
We can now deploy a Kubernetes charm. For example, here we deploy a charm by requesting the use of the ‘mariadb-pv’ workload storage pool we just set up:
juju deploy cs:~juju/mariadb-k8s --storage database=10M
Verify deployment
The output to juju status should soon look like the following:
Model Controller Cloud/Region Version SLA Timestamp
k8s-model mk8s microk8s 2.6-beta2 unsupported 14:47:20Z
App Version Status Scale Charm Store Rev OS Address Notes
mariadb-k8s active 1 mariadb-k8s jujucharms 1 kubernetes 10.152.183.153
Unit Workload Agent Address Ports Message
mariadb-k8s/0* active idle 10.1.1.15 3306/TCP
In contrast to standard Juju behaviour, there are no machines listed here. Let’s see what has happened within the cluster:
microk8s.kubectl get all --all-namespaces
New sample output:
NAMESPACE NAME READY STATUS RESTARTS AGE
controller-mk8s pod/controller-0 2/2 Running 1 6m6s
k8s-model pod/mariadb-k8s-0 1/1 Running 0 77s
k8s-model pod/mariadb-k8s-operator-0 1/1 Running 0 93s
kube-system pod/hostpath-provisioner-6d744c4f7c-t9hgh 1/1 Running 0 9m39s
kube-system pod/kube-dns-6bfbdd666c-rxnp9 3/3 Running 0 9m45s
NAMESPACE NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
controller-mk8s service/controller-service ClusterIP 10.152.183.168 <none> 17070/TCP 6m7s
default service/kubernetes ClusterIP 10.152.183.1 <none> 443/TCP 10m
testing service/mariadb-k8s ClusterIP 10.152.183.153 <none> 3306/TCP 76s
kube-system service/kube-dns ClusterIP 10.152.183.10 <none> 53/UDP,53/TCP 9m45s
NAMESPACE NAME READY UP-TO-DATE AVAILABLE AGE
kube-system deployment.apps/hostpath-provisioner 1/1 1 1 9m39s
kube-system deployment.apps/kube-dns 1/1 1 1 9m45s
NAMESPACE NAME DESIRED CURRENT READY AGE
kube-system replicaset.apps/hostpath-provisioner-6d744c4f7c 1 1 1 9m39s
kube-system replicaset.apps/kube-dns-6bfbdd666c 1 1 1 9m45s
NAMESPACE NAME READY AGE
controller-mk8s statefulset.apps/controller 1/1 6m6s
testing statefulset.apps/mariadb-k8s 1/1 77s
testing statefulset.apps/mariadb-k8s-operator 1/1 93s
You can easily identify the changes, as compared to the initial output, by scanning the left-hand side for our model name ‘k8s-model’, which runs in a Kubernetes namespace of the same name. The operator/controller pod runs in a namespace whose name is based on our controller name (‘mk8s’): “controller-mk8s”.
To get information on pod ‘mariadb-k8s-0’ you need to refer to the namespace (since it’s not the ‘default’ namespace) in this way:
microk8s.kubectl describe pods -n testing mariadb-k8s-0
The output is too large to sensibly include here. See the upstream documentation on different ways of viewing cluster information.
Remove configuration and software
To remove all traces of what we’ve done in this tutorial, use the following commands:
juju kill-controller -y -t 0 micro
microk8s.reset
sudo snap remove microk8s
sudo snap remove juju
That’s the end of this tutorial!
Next steps
- Learn more about using Kubernetes with Juju
Last updated 5 months ago.