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kustomize/examples/multibases/README.md

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# Demo: multibases with a common base
`kustomize` encourages defining multiple variants -
e.g. dev, staging and prod,
as overlays on a common base.
It's possible to create an additional overlay to
compose these variants together - just declare the
overlays as the bases of a new kustomization.
This is also a means to apply a common label or
annotation across the variants, if for some reason
the base isn't under your control. It also allows
one to define a left-most namePrefix across the
variants - something that cannot be
done by modifying the common base.
The following demonstrates this using a base
that is just a single pod.
Define a place to work:
<!-- @makeWorkplace @testAgainstLatestRelease -->
```
DEMO_HOME=$(mktemp -d)
```
Define a common base:
<!-- @makeBase @testAgainstLatestRelease -->
```
BASE=$DEMO_HOME/base
mkdir $BASE
cat <<EOF >$BASE/kustomization.yaml
resources:
- pod.yaml
EOF
cat <<EOF >$BASE/pod.yaml
apiVersion: v1
kind: Pod
metadata:
name: myapp-pod
labels:
app: myapp
spec:
containers:
- name: nginx
image: nginx:1.7.9
EOF
```
Define a dev variant overlaying base:
<!-- @makeDev @testAgainstLatestRelease -->
```
DEV=$DEMO_HOME/dev
mkdir $DEV
cat <<EOF >$DEV/kustomization.yaml
resources:
- ./../base
namePrefix: dev-
EOF
```
Define a staging variant overlaying base:
<!-- @makeStaging @testAgainstLatestRelease -->
```
STAG=$DEMO_HOME/staging
mkdir $STAG
cat <<EOF >$STAG/kustomization.yaml
resources:
- ./../base
namePrefix: stag-
EOF
```
Define a production variant overlaying base:
<!-- @makeProd @testAgainstLatestRelease -->
```
PROD=$DEMO_HOME/production
mkdir $PROD
cat <<EOF >$PROD/kustomization.yaml
resources:
- ./../base
namePrefix: prod-
EOF
```
Then define a _Kustomization_ composing three variants together:
<!-- @makeTopLayer @testAgainstLatestRelease -->
```
cat <<EOF >$DEMO_HOME/kustomization.yaml
resources:
- ./dev
- ./staging
- ./production
namePrefix: cluster-a-
EOF
```
Now the workspace has following directories
> ```
> .
> ├── base
> │   ├── kustomization.yaml
> │   └── pod.yaml
> ├── dev
> │   └── kustomization.yaml
> ├── kustomization.yaml
> ├── production
> │   └── kustomization.yaml
> └── staging
> └── kustomization.yaml
> ```
Confirm that the `kustomize build` output contains three pod objects from dev, staging and production variants.
<!-- @confirmVariants @testAgainstLatestRelease -->
```
test 1 == \
$(kustomize build $DEMO_HOME | grep cluster-a-dev-myapp-pod | wc -l); \
echo $?
test 1 == \
$(kustomize build $DEMO_HOME | grep cluster-a-stag-myapp-pod | wc -l); \
echo $?
test 1 == \
$(kustomize build $DEMO_HOME | grep cluster-a-prod-myapp-pod | wc -l); \
echo $?
```
Similarly to adding different `namePrefix` in different variants, one can also add different `namespace` and compose those variants in
one _kustomization_. For more details, take a look at [multi-namespaces](multi-namespace.md).