CODEWITHSUNDEEP
kubernetes
Will Squire
Will Squire

Reputation: 6595

Use relative paths in Kubernetes config

The goal is to orchestrate both production and local development environments using Kubernetes. The problem is that hostPath doesn't work with relative path values. This results in slightly differing configuration files on each developer's machine to accommodate for the different project locations (i.e. "/my/absolute/path/to/the/project"): 

apiVersion: v1
kind: Service
metadata:
  name: some-service
  labels:
    app: app
spec:
  type: LoadBalancer
  ports:
  - port: 80
  selector:
    app: app
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: some-deploy
spec:
  selector:
    matchLabels:
      app: app
  replicas: 1
  template:
    metadata:
      labels:
        app: app
    spec:
      containers:
      - name: app
        image: nginx:1.13.12-alpine
        ports:
        - containerPort: 80
        volumeMounts:
        - name: vol_example
          mountPath: /var/www/html
      volumes:
        - name: vol_example
          hostPath:
            path: "/my/absolute/path/to/the/project"
            type: Directory

How can relative paths be used in Kubernetes config files? Variable replacements (such as $(PWD)/project) have been tried, but didn't seem to work. If config variables can work with volumes, this might help but unsure of how to achieve this.

Upvotes: 33

Views: 15648

Answers (2)

Nomios
Nomios

Reputation: 181

Not a native Kubernetes solution but you can manually edit the .yaml file 'on-the-fly' before applying it with kubectl. In your .yaml file use a substitution that is not likely to become ambiguous in the volume section:

volumes:
  - name: vol_example
    hostPath:
      path: {{path}}/relative/path
      type: Directory

Then to apply the manifest run:

 cat deployment.yaml | sed s+{{path}}+$(pwd)+g | kubectl apply -f -

Note: sed is used with the separator + because $(pwd) will result in a path that includes one or more / which is the conventional sed separator.

Upvotes: 2

bits
bits

Reputation: 1705

As mentioned here kubectl will never support variable substitution.

You can create a helm chart for your app (yaml). It supports yaml template variables (among various other features). So you'll be able to pass hostPath parameter based on development or production.

Upvotes: 7

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