my-docs/Containerization-Orchestration/Kubernetes/Storage/emptydir_vol.md

📦 Pod Volume Lifecycle & emptyDir Usage in Kubernetes

This document describes how volumes work in the context of Kubernetes Pods, focusing on emptyDir and its lifecycle behavior.

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🔁 Pod Lifecycle & Volumes

• Volumes are defined at the Pod level. They are not tied to a specific container, but can be shared among containers within the same Pod.

• Volumes are attached to containers through volumeMounts. This enables containers to access the volume’s filesystem at the specified mountPath.

• Data in emptyDir volumes is ephemeral. The volume is created when the Pod starts and deleted when the Pod is removed, erasing all stored data.

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⚠️ Visibility Across Pods & Containers

• A Pod cannot access another Pod’s volume, even if it's of type emptyDir. For example:

  • Pod A cannot see Pod B’s emptyDir.

• However, containers within the same Pod can share and access the same emptyDir volume.

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🧪 Example: Pod with emptyDir Volume in Memory

apiVersion: v1
kind: Pod
metadata:
  namespace: ns-test
  name: pod-tests
spec:
  containers:
    - name: nginx
      image: nginx
      resources:
        limits:
          memory: "150Mi"
          cpu: "500m"
      volumeMounts:
        - name: nginx-log
          mountPath: /var/log/nginx
  volumes:
    - name: nginx-log
      emptyDir:
        medium: Memory  # Uses memory for faster read/write operations
        sizeLimit: 64Mi # Volume size limited to 64Mi

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🧠 Key Points

• emptyDir is ideal for temporary storage like logs, scratch space, or caches.
• Using medium: Memory stores data in memory (RAM) instead of disk, offering higher performance.
• sizeLimit restricts the amount of memory that the emptyDir can consume.