In case of a single ubuntu VM, add the required subdomain to /etc/hosts
$ sudo sed -i '/^127.0.0.1/ s/$/ configmap-web\.k3sdemo\.lan/' /etc/hosts
create namespace for configmap tests
$ kubectl create namespace configmaps
namespace/configmaps created
Create configmap with two variables and values.
$ kubectl -n configmaps create configmap nginx-env --from-literal=my-var1=test --from-literal=my-var2=two
configmap/nginx-env created
$ kubectl -n configmaps get configmaps nginx-env -o yaml
apiVersion: v1
data:
my-var1: test
my-var2: two
kind: ConfigMap
metadata:
creationTimestamp: "2020-05-15T18:12:26Z"
managedFields:
- apiVersion: v1
fieldsType: FieldsV1
fieldsV1:
f:data:
.: {}
f:my-var1: {}
f:my-var2: {}
manager: kubectl
operation: Update
time: "2020-05-15T18:12:26Z"
name: nginx-env
namespace: configmaps
resourceVersion: "160290"
selfLink: /api/v1/namespaces/configmaps/configmaps/nginx-env
uid: dfe825bb-fb9c-4cbf-9e9e-ff0da3166322
Download the index.html
$ curl -k https://my-webserver.k3s-demo.lan/ > index.html
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 612 100 612 0 0 14926 0 --:--:-- --:--:-- --:--:-- 14926
Edit the index html. We will exchange it by a configmap.
$ vi index.html
Create a configmap with the edited index.html.
$ kubectl -n configmaps create configmap nginx-index --from-file=index.html=index.html
configmap/nginx-index created
dgo@dgo-VirtualBox:~$ kubectl -n configmaps get configmap nginx-index -o yaml
apiVersion: v1
data:
index.html: |
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
width: 35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
<body>
<p><center>index.html from configmap</center></p>
<hr>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
kind: ConfigMap
metadata:
creationTimestamp: "2020-05-15T18:13:48Z"
managedFields:
- apiVersion: v1
fieldsType: FieldsV1
fieldsV1:
f:data:
.: {}
f:index.html: {}
manager: kubectl
operation: Update
time: "2020-05-15T18:13:48Z"
name: nginx-index
namespace: configmaps
resourceVersion: "160480"
selfLink: /api/v1/namespaces/configmaps/configmaps/nginx-index
uid: 92daa345-be2d-4514-b4fa-09b3a8c89be9
A configmap can contain literals and files.
$ kubectl -n configmaps create configmap nginx --from-file=index.html=index.html --from-literal=my-var1=test --from-literal=my-var2=two
configmap/nginx created
$ kubectl -n configmaps get configmaps nginx -o yaml
apiVersion: v1
data:
index.html: |
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
width: 35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
<body>
<p><center>index.html from configmap</center></p>
<hr>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
my-var1: test
my-var2: two
kind: ConfigMap
metadata:
creationTimestamp: "2020-05-15T18:15:01Z"
managedFields:
- apiVersion: v1
fieldsType: FieldsV1
fieldsV1:
f:data:
.: {}
f:index.html: {}
f:my-var1: {}
f:my-var2: {}
manager: kubectl
operation: Update
time: "2020-05-15T18:15:01Z"
name: nginx
namespace: configmaps
resourceVersion: "160657"
selfLink: /api/v1/namespaces/configmaps/configmaps/nginx
uid: c763e09d-b974-4172-aed8-f3f6a8be5a7b
Delete the configmaps.
$ kubectl -n configmaps delete configmaps nginx-env
configmap "nginx-env" deleted
$ kubectl -n configmaps delete configmaps nginx-index
configmap "nginx-index" deleted
$ kubectl -n configmaps delete configmaps nginx
configmap "nginx" deleted
Create a configmap by a yaml-file.
$ cat <<EOF | kubectl -n configmaps apply -f -
apiVersion: v1
data:
index.html: |
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
width: 35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
<body>
<p><center>index.html from configmap</center></p>
<hr>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
my-var1: test
my-var2: two
kind: ConfigMap
metadata:
name: nginx
EOF
Clean up and delete the namespace configmaps.
$ kubectl delete namespace configmaps
namespace "configmaps" deleted
Review the contents of the directory k3s-demo/applications/configmaps/ The configMapGenerator of kustomize will be used to create the configmap.
$ cd ~/k3s-demo/applications/configmaps/
$ ls -l index.html
-rw-rw-r-- 1 dgo dgo 667 Mai 15 16:13 index.html
$ cat kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
namespace: configmaps
resources:
- deployment-configmap-web.yaml
- ingress-configmap-web.yaml
- namespace-configmaps.yaml
- service-configmap-web.yaml
configMapGenerator:
- name: nginx
literals:
- my-var1=test
- my-var2=two
files:
- index.html=index.html
generatorOptions:
disableNameSuffixHash: true
Review the output of kustomize build wth the new configmap. The deployment contains a volume mount for the index.html and it imports the variables from the configmap.
$ kustomize build .
Create the ressources with kubectl apply -k . and review the results.
$ kubectl create -k .
namespace/configmaps created
configmap/nginx created
service/configmap-web created
deployment.apps/configmap-web created
ingress.extensions/ingress-configmap-web created
$ kubectl -n configmaps get pod
NAME READY STATUS RESTARTS AGE
configmap-web-7f74946c78-mmg44 1/1 Running 0 15s
$ kubectl -n configmaps exec configmap-web-7f74946c78-mmg44 -- env | grep VARIABLE
VARIABLE1=test
VARIABLE2=two
$ curl -k https://configmap-web.k3s-demo.lan
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
width: 35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
<body>
<p><center>index.html from configmap</center></p>
<hr>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>