ansible-role-k3s/documentation/quickstart-cluster.md

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# Quickstart: K3s cluster with a single control node
This is the quickstart guide to creating your own k3s cluster with one control
plane node. This control plane node will also be a worker.
:hand: This example requires your Ansible user to be able to connect to the
servers over SSH using key-based authentication. The user is also has an entry
in a sudoers file that allows privilege escalation without requiring a
password.
To test this is the case, run the following check replacing `<ansible_user>`
and `<server_name>`. The expected output is `Works`
`ssh <ansible_user>@<server_name> 'sudo cat /etc/shadow >/dev/null && echo "Works"'`
For example:
```text
[ xmanning@dreadfort:~/git/kubernetes-playground ] (master) $ ssh ansible@kube-0 'sudo cat /etc/shadow >/dev/null && echo "Works"'
Works
[ xmanning@dreadfort:~/git/kubernetes-playground ] (master) $
```
## Directory structure
Our working directory will have the following files:
```text
kubernetes-playground/
|_ inventory.yml
|_ cluster.yml
```
## Inventory
Here's a YAML based example inventory for our servers called `inventory.yml`:
```yaml
---
k3s_cluster:
hosts:
kube-0:
ansible_user: ansible
ansible_host: 10.10.9.2
ansible_python_interpreter: /usr/bin/python3
kube-1:
ansible_user: ansible
ansible_host: 10.10.9.3
ansible_python_interpreter: /usr/bin/python3
kube-2:
ansible_user: ansible
ansible_host: 10.10.9.4
ansible_python_interpreter: /usr/bin/python3
```
We can test this works with `ansible -i inventory.yml -m ping all`, expected
result:
```text
kube-0 | SUCCESS => {
"changed": false,
"ping": "pong"
}
kube-1 | SUCCESS => {
"changed": false,
"ping": "pong"
}
kube-2 | SUCCESS => {
"changed": false,
"ping": "pong"
}
```
## Playbook
Here is our playbook for the k3s cluster (`cluster.yml`):
```yaml
---
- name: Build a cluster with a single control node
hosts: k3s_cluster
vars:
k3s_become_for_all: true
roles:
- role: xanmanning.k3s
```
## Execution
To execute the playbook against our inventory file, we will run the following
command:
`ansible-playbook -i inventory.yml cluster.yml`
The output we can expect is similar to the below, with no failed or unreachable
nodes. The default behavior of this role is to delegate the first play host as
the control node, so kube-0 will have more changed tasks than others:
```text
PLAY RECAP *******************************************************************************************************
kube-0 : ok=56 changed=11 unreachable=0 failed=0 skipped=28 rescued=0 ignored=0
kube-1 : ok=43 changed=10 unreachable=0 failed=0 skipped=32 rescued=0 ignored=0
kube-2 : ok=43 changed=10 unreachable=0 failed=0 skipped=32 rescued=0 ignored=0
```
## Testing
After logging into kube-0, we can test that k3s is running across the cluster,
that all nodes are ready and that everything is ready to execute our Kubernetes
workloads by running the following:
- `sudo kubectl get nodes -o wide`
- `sudo kubectl get pods -o wide --all-namespaces`
:hand: Note we are using `sudo` because we need to be root to access the
kube config for this node. This behavior can be changed with specifying
`write-kubeconfig-mode: 0644` in `k3s_server`.
**Get Nodes**:
```text
ansible@kube-0:~$ sudo kubectl get nodes -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
kube-0 Ready master 34s v1.19.4+k3s1 10.0.2.15 <none> Ubuntu 20.04.1 LTS 5.4.0-56-generic containerd://1.4.1-k3s1
kube-2 Ready <none> 14s v1.19.4+k3s1 10.0.2.17 <none> Ubuntu 20.04.1 LTS 5.4.0-56-generic containerd://1.4.1-k3s1
kube-1 Ready <none> 14s v1.19.4+k3s1 10.0.2.16 <none> Ubuntu 20.04.1 LTS 5.4.0-56-generic containerd://1.4.1-k3s1
ansible@kube-0:~$
```
**Get Pods**:
```text
ansible@kube-0:~$ sudo kubectl get pods -o wide --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
kube-system local-path-provisioner-7ff9579c6-72j8x 1/1 Running 0 55s 10.42.2.2 kube-1 <none> <none>
kube-system metrics-server-7b4f8b595-lkspj 1/1 Running 0 55s 10.42.1.2 kube-2 <none> <none>
kube-system helm-install-traefik-b6vnt 0/1 Completed 0 55s 10.42.0.3 kube-0 <none> <none>
kube-system coredns-66c464876b-llsh7 1/1 Running 0 55s 10.42.0.2 kube-0 <none> <none>
kube-system svclb-traefik-jrqg7 2/2 Running 0 27s 10.42.1.3 kube-2 <none> <none>
kube-system svclb-traefik-gh65q 2/2 Running 0 27s 10.42.0.4 kube-0 <none> <none>
kube-system svclb-traefik-5z7zp 2/2 Running 0 27s 10.42.2.3 kube-1 <none> <none>
kube-system traefik-5dd496474-l2k74 1/1 Running 0 27s 10.42.1.4 kube-2 <none> <none>
```