ansible-role-k3s/documentation/quickstart-single-node.md
2022-01-07 13:34:40 -03:00

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# Quickstart: K3s single node
This is the quickstart guide to creating your own single-node k3s "cluster".
:hand: This example requires your Ansible user to be able to connect to the
server 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
|_ single_node.yml
```
## Inventory
Here's a YAML based example inventory for our server called `inventory.yml`:
```yaml
---
k3s_cluster:
hosts:
kube-0:
ansible_user: ansible
ansible_host: 10.10.9.2
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"
}
```
## Playbook
Here is our playbook for a single node k3s cluster (`single_node.yml`):
```yaml
---
- name: Build a single node k3s cluster
hosts: kube-0
vars:
k3s_become: 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 single_node.yml`
The output we can expect is similar to the below, with no failed or unreachable
nodes:
```text
PLAY RECAP *******************************************************************************************************
kube-0 : ok=39 changed=8 unreachable=0 failed=0 skipped=39 rescued=0 ignored=0
```
## Testing
After logging into the server, we can test that k3s is running and that it is
ready to execute our Kubernetes workloads by running the following:
- `sudo kubectl get nodes`
- `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
NAME STATUS ROLES AGE VERSION
kube-0 Ready master 5m27s v1.19.4+k3s
ansible@kube-0:~$
```
**Get Pods**:
```text
ansible@kube-0:~$ sudo kubectl get pods --all-namespaces -o wide
NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
kube-system metrics-server-7b4f8b595-k692h 1/1 Running 0 9m38s 10.42.0.2 kube-0 <none> <none>
kube-system local-path-provisioner-7ff9579c6-5lgzb 1/1 Running 0 9m38s 10.42.0.3 kube-0 <none> <none>
kube-system coredns-66c464876b-xg42q 1/1 Running 0 9m38s 10.42.0.5 kube-0 <none> <none>
kube-system helm-install-traefik-tdpcs 0/1 Completed 0 9m38s 10.42.0.4 kube-0 <none> <none>
kube-system svclb-traefik-hk248 2/2 Running 0 9m4s 10.42.0.7 kube-0 <none> <none>
kube-system traefik-5dd496474-bf4kv 1/1 Running 0 9m4s 10.42.0.6 kube-0 <none> <none>
```