A Practical Guide to Kubernetes/

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Defining Pods through Declarative Syntax

Defining Pods through Declarative Syntax

Learn to create Pods using declarative syntax.

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Pods as wrappers for containers

Even though a Pod can contain any number of containers, the most common use case is to use the single-container-in-a-Pod model. In such a case, a Pod is a wrapper around one container. From Kubernetes’ perspective, a Pod is the smallest unit. We cannot tell Kubernetes to run a container. Instead, we ask it to create a Pod that wraps around a container.

Looking into a Pod’s definition

Let’s look at a simple Pod db.yml definition:

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apiVersion: v1
kind: Pod
metadata:
  name: db
  labels:
    type: db
    vendor: MongoLabs
spec:
  containers:
  - name: db
    image: mongo:3.3
    command: ["mongod"]
    args: ["--rest", "--httpinterface"]

Let’s analyze the various sections in the output definition of a Pod:

  • Lines 1–2: We use v1 of Kubernetes Pods API. Both apiVersion and kind are mandatory. That way, Kubernetes knows what we want to do (create a Pod) and which API version to use.

  • Lines 3–7: The next ...