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Storage Ephemeral

Temporary storage in Kubernetes, tied to a Pod’s lifecycle.

Ephemeral Storage in Kubernetes pertains to temporary storage that is associated with each container running in a Pod. It is transient and is lost once the container or the Pod is terminated.

Characteristics

  • Transient Nature: Any data stored is temporary and is lost when the container or Pod ceases to exist.
  • Default Storage: Containers are equipped with ephemeral storage by default, but additional configurations are needed for persistence.
  • Volume Configuration: Volumes can be configured in deployment files to use ephemeral storage, typically represented by emptyDir: {}.

Use Cases

  • Temporary File Storage: Ephemeral storage is ideal for temporary data and cache files that do not need to persist between container restarts.
  • Working Directory: Containers utilize ephemeral storage as a working directory for operations like CRUD operations on files and logs.

Configuration Examples

  • Volume Configuration with emptyDir

Here, myVolume is ephemeral and is mounted at /app/data in the container. Data stored here will be lost once the container or Pod is terminated.

apiVersion: v1
kind: Pod
metadata:
 name: myapp-pod
spec:
 containers:
 - name: myapp-container
   image: myapp:1.0
   volumeMounts:
   - name: myVolume
     mountPath: /app/data
 volumes:
 - name: myVolume
   emptyDir: {}
  • Specifying a Working Directory

This specifies /app as the working directory of the container, which might be used for temporary file operations and overrides any WORKDIR set in the Dockerfile.

apiVersion: v1
kind: Pod
metadata:
 name: myapp-pod
spec:
 containers:
 - name: myapp-container
   image: myapp:1.0
   workingDir: /app  # Overrides the WORKDIR specified in the Dockerfile