Please read this great post about the todo list demo app, it was tested on k3s 1.17.2, eks 1.14 and rke 1.15:
You should understand how the secrets, configmaps and deployment manifests was built and what they do!
Expand here to see the solution
k create -f db-credentials-secret.yaml
k create -f db-root-credentials-secret.yaml
k create -f mysql-configmap.yaml
k create -f mysql-deployment.yaml
k get all
k get pvc
k get pv
k create -f backend-deployment.yaml
k get pods
k get svc
vi backend-configmap.yaml
k create -f backend-configmap.yaml
k create -f frontend-deployment.yaml
k get svc