Creating Your First Kustomization
This page will help you get started with this amazing tool called kustomize! You will start off with a simple nginx deployment manifest and then use it to explore kustomize basics.
Create resource manifests and Kustomization
Let’s start off by creating your nginx deployment and service manifests in a dedicated folder:
mkdir kustomize-example
cd kustomize-example
cat <<'EOF' >deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: nginx
name: nginx
spec:
replicas: 1
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- image: nginx
name: nginx
ports:
- containerPort: 80
EOF
cat <<'EOF' >service.yaml
apiVersion: v1
kind: Service
metadata:
labels:
app: nginx
name: nginx
spec:
ports:
- port: 80
protocol: TCP
targetPort: 80
selector:
app: nginx
EOF
Now that you have your deployment.yaml and service.yaml files created, let’s create your Kustomization. You can think of Kustomization as the set of instructions that tell kustomize what it needs to do, and it is defined in a file named kustomization.yaml:
cat <<'EOF' >kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- deployment.yaml
- service.yaml
EOF
In this kustomization file, you are telling kustomize to include the deployment.yaml and service.yaml as its resources. If you now run kustomize build . from your current working directory, kustomize will generate a manifest containing the contents of your deployment.yaml and service.yaml files with no additional changes.
$ kustomize build .
apiVersion: v1
kind: Service
metadata:
labels:
app: nginx
name: nginx
spec:
ports:
- port: 80
protocol: TCP
targetPort: 80
selector:
app: nginx
---
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: nginx
name: nginx
spec:
replicas: 1
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- image: nginx
name: nginx
ports:
- containerPort: 80
Customize resources
So far kustomize has not been used to do any modifications, so let’s see how you can do that. Kustomize comes with a considerable number of transformers that apply changes to your manifests, and in this section you will have a look at the namePrefix transformer. This transformer will add a prefix to the deployment and service names. Modify the kustomization.yaml file as follows:
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
namePrefix: example- ### add this line
resources:
- deployment.yaml
- service.yaml
After re-building you see can see your modified manifest which now has the prefixed deployment and service names:
$ kustomize build .
apiVersion: v1
kind: Service
metadata:
labels:
app: nginx
name: example-nginx ### service name changed here
spec:
ports:
- port: 80
protocol: TCP
targetPort: 80
selector:
app: nginx
---
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: nginx
name: example-nginx ### deployment name changed here
spec:
replicas: 1
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- image: nginx
name: nginx
ports:
- containerPort: 80
Create variants using overlays
Now let’s assume that you need to deploy the nginx manifests from the previous section to two environments called Staging and Production. The manifests for these two environments will be mostly identical, with only a few minor changes between them. These two mostly identical manifests are called “variants”. Traditionally, to create variants you could duplicate the manifests and apply the changes manually or rely on some templating engine. With kustomize you can avoid templating and duplication of your manifests and apply the different changes you need using overlays. With this approach, the base contains what your environments have in common, and the overlays contain your environment-specific changes.
Create the kustomization.yaml files for your two overlays and move the files you have so far into base:
mkdir -p base overlays/staging overlays/production
mv deployment.yaml kustomization.yaml service.yaml base
cat <<'EOF' >overlays/staging/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- ../../base
EOF
cat <<'EOF' >overlays/production/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- ../../base
EOF
The kustomization files for the overlays include just the base folder, so if you were to run kustomize build on the overlay folders at this point you would get the same output you would get if you built base. It is important to note that bases can be included in the resources field in the same way that your other deployment and service resource files were included.
The directory structure you created so far should look like this:
kustomize-example
├── base
│ ├── deployment.yaml
│ ├── kustomization.yaml
│ └── service.yaml
└── overlays
├── production
│ └── kustomization.yaml
└── staging
└── kustomization.yaml
Customizing overlays
For the purposes of this example, let’s define some requirements for how your deployment should look like in the two environments:
| Requirement | Production | Staging |
|---|---|---|
| Name | env1-example-nginx-production | env2-example-nginx-staging |
| Namespace | production | staging |
| Replicas | 3 | 2 |
You can achieve the names required by making use of namePrefix and nameSuffix as follows:
kustomize-example/overlays/production/kustomization.yaml:
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
namePrefix: env1-
nameSuffix: -production
resources:
- ../../base
kustomize-example/overlays/staging/kustomization.yaml:
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
namePrefix: env2-
nameSuffix: -staging
resources:
- ../../base
The build output for your Production overlay would now be:
$ kustomize build overlays/production/
apiVersion: v1
kind: Service
metadata:
labels:
app: nginx
name: env1-example-nginx-production ### service name changed here
spec:
ports:
- port: 80
protocol: TCP
targetPort: 80
selector:
app: nginx
---
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: nginx
name: env1-example-nginx-production ### deployment name changed here
spec:
replicas: 1
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- image: nginx
name: nginx
ports:
- containerPort: 80
It is important to note here that the name for both the deployment and the service were updated with the namePrefix and nameSuffix defined. If you had additional Kubernetes objects (like an ingress) their name would be updated as well.
Moving on to the next requirements, you can set the namespace and the number of replicas you want by using namespace and replicas respectively:
kustomize-example/overlays/production/kustomization.yaml:
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
namePrefix: env1-
nameSuffix: -production
namespace: production
replicas:
- name: example-nginx
count: 3
resources:
- ../../base
kustomize-example/overlays/staging/kustomization.yaml:
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
namePrefix: env2-
nameSuffix: -staging
namespace: staging
replicas:
- name: example-nginx
count: 2
resources:
- ../../base
Note that the deployment name being referenced in replicas is the modified name that was output by base. Looking at the output of kustomize build you can see that all the requirements that were set have been met:
Production overlay build:
$ kustomize build overlays/production/
apiVersion: v1
kind: Service
metadata:
labels:
app: nginx
name: env1-example-nginx-production
namespace: production ### namespace has been set to production
spec:
ports:
- port: 80
protocol: TCP
targetPort: 80
selector:
app: nginx
---
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: nginx
name: env1-example-nginx-production
namespace: production ### namespace has been set to production
spec:
replicas: 3 ### replicas have been updated from 1 to 3
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- image: nginx
name: nginx
ports:
- containerPort: 80
Staging overlay build:
$ kustomize build overlays/staging/
apiVersion: v1
kind: Service
metadata:
labels:
app: nginx
name: env2-example-nginx-staging
namespace: staging ### namespace has been set to staging
spec:
ports:
- port: 80
protocol: TCP
targetPort: 80
selector:
app: nginx
---
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: nginx
name: env2-example-nginx-staging
namespace: staging ### namespace has been set to staging
spec:
replicas: 2 ### replicas have been updated from 1 to 2
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- image: nginx
name: nginx
ports:
- containerPort: 80
Further customizations
Now that you have seen how kustomize works, let’s add a few more requirements:
| Requirement | Production | Staging |
|---|---|---|
| Image | nginx:1.20.2 | nginx:latest |
| Label | variant=var1 | variant=var2 |
| Env Var | ENVIRONMENT=prod | ENVIRONMENT=stg |
To keep the example brief, only the changes for the Production overlay will be shown and then the updated overlay files and builds for both overlays will be presented at the end. The specific image tag can be set by making use of the images field. Add the following to the kustomization files in your overlays:
images:
- name: nginx
newTag: 1.20.2 ## For the Staging overlay set this to 'latest'
For setting the label, you can use the labels field. Add the following to the kustomization files in your overlays:
labels:
- pairs:
variant: var1 ## For the Staging overlay set this to 'var2'
includeSelectors: false # Setting this to false so that the label is not added to the selectors
includeTemplates: true # Setting this to true will make the label available also on the pod and not just the deployment
At this point, your kustomization files for your Production overlay should be as follows:
kustomize-example/overlays/production/kustomization.yaml:
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
namePrefix: env1-
nameSuffix: -production
namespace: production
replicas:
- name: example-nginx
count: 3
images:
- name: nginx
newTag: 1.20.2
labels:
- pairs:
variant: var1
includeSelectors: false
includeTemplates: true
resources:
- ../../base
Rebuilding the Production overlay gives the following:
$ kustomize build overlays/production/
apiVersion: v1
kind: Service
metadata:
labels:
app: nginx
variant: var1 ### label has been set here
name: env1-example-nginx-production
namespace: production
spec:
ports:
- port: 80
protocol: TCP
targetPort: 80
selector:
app: nginx
---
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: nginx
variant: var1 ### label has been set here
name: env1-example-nginx-production
namespace: production
spec:
replicas: 3
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
variant: var1 ### label has been set here
spec:
containers:
- image: nginx:1.20.2 ### image tag has been set to 1.20.2
name: nginx
ports:
- containerPort: 80
The last requirement to meet is to set the environment variable, and to do that you will create a patch. To do this, create the following file for the Production overlay:
cat <<'EOF' >overlays/production/patch-env-vars.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: example-nginx
spec:
template:
spec:
containers:
- name: nginx
env:
- name: ENVIRONMENT
value: prod
EOF
Next step, add a reference to that patch file in kustomization.yaml:
patches:
- path: patch-env-vars.yaml
One important thing to note here is that the name of the deployment used is the name that you are getting from the base and not the deployment name that has the prefix and suffix added.
Rebuilding the overlay shows that the environment variable has been added to your container:
$ kustomize build overlays/production/
apiVersion: v1
kind: Service
metadata:
labels:
app: nginx
variant: var1
name: env1-example-nginx-production
namespace: production
spec:
ports:
- port: 80
protocol: TCP
targetPort: 80
selector:
app: nginx
---
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: nginx
variant: var1
name: env1-example-nginx-production
namespace: production
spec:
replicas: 3
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
variant: var1
spec:
containers:
- env:
- name: ENVIRONMENT ### Environment variable has been added here
value: prod
image: nginx:1.20.2
name: nginx
ports:
- containerPort: 80
Looking at the output of kustomize build you can see that the additional requirements that were set have now been met. Below are the files as they should be at this point in your overlays and the kustomize build output:
kustomize-example/overlays/production/kustomization.yaml:
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
namePrefix: env1-
nameSuffix: -production
namespace: production
replicas:
- name: example-nginx
count: 3
images:
- name: nginx
newTag: 1.20.2
labels:
- pairs:
variant: var1
includeSelectors: false
includeTemplates: true
resources:
- ../../base
patches:
- path: patch-env-vars.yaml
kustomize-example/overlays/production/patch-env-vars.yaml:
apiVersion: apps/v1
kind: Deployment
metadata:
name: example-nginx
spec:
template:
spec:
containers:
- name: nginx
env:
- name: ENVIRONMENT
value: prod
kustomize-example/overlays/staging/kustomization.yaml:
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
namePrefix: env2-
nameSuffix: -staging
namespace: staging
replicas:
- name: example-nginx
count: 2
images:
- name: nginx
newTag: latest
labels:
- pairs:
variant: var2
includeSelectors: false
includeTemplates: true
resources:
- ../../base
patches:
- path: patch-env-vars.yaml
kustomize-example/overlays/staging/patch-env-vars.yaml:
apiVersion: apps/v1
kind: Deployment
metadata:
name: example-nginx
spec:
template:
spec:
containers:
- name: nginx
env:
- name: ENVIRONMENT
value: stg
Production overlay build:
$ kustomize build overlays/production/
apiVersion: v1
kind: Service
metadata:
labels:
app: nginx
variant: var1
name: env1-example-nginx-production
namespace: production
spec:
ports:
- port: 80
protocol: TCP
targetPort: 80
selector:
app: nginx
---
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: nginx
variant: var1
name: env1-example-nginx-production
namespace: production
spec:
replicas: 3
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
variant: var1
spec:
containers:
- env:
- name: ENVIRONMENT
value: prod
image: nginx:1.20.2
name: nginx
ports:
- containerPort: 80
Staging overlay build:
$ kustomize build overlays/staging/
apiVersion: v1
kind: Service
metadata:
labels:
app: nginx
variant: var2
name: env2-example-nginx-staging
namespace: staging
spec:
ports:
- port: 80
protocol: TCP
targetPort: 80
selector:
app: nginx
---
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: nginx
variant: var2
name: env2-example-nginx-staging
namespace: staging
spec:
replicas: 2
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
variant: var2
spec:
containers:
- env:
- name: ENVIRONMENT
value: stg
image: nginx:latest
name: nginx
ports:
- containerPort: 80
Next steps
Congratulations on making it to the end of this tutorial. As a summary for you, these are the customizations that were presented in this tutorial:
- Add a name prefix and a name suffix
- Set the namespace for your resources
- Set the number of replicas for your deployment
- Set the image to use
- Add a label to your resources
- Add an environment variable to a container by using a patch
These are just a few of the things kustomize can do. If you are interested to learn more, the kustomization reference is your next step. You will see how you can use components to define base resources and add them to specific overlays where needed, use generators to create configMaps from files, and much more!
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