Volumes: emptyDir and hostPath

Storage / Guide 65 of 103 / Beginner

• Kubernetes1.36.4
• Cluster4 nodes
• Runtimecontainerd 2.2.6
• CNICalico v3.32.1
• TimeAbout 30 min

Disk sizes are this lab's. The lifetime rules are properties of the volume types.

This guide includes

Use this when two containers in a Pod have to share files, or when something needs to reach the node's own filesystem. This matters because an emptyDir dies with the Pod and a hostPath is a different directory on every node - so neither is storage you can actually rely on.

• declaring a volume once at Pod level and mounting it separately inside each container
• deleting the Pod and confirming the emptyDir went with it
• writing through a hostPath and proving it landed on the node's own filesystem
• mounting that same hostPath on a second node and finding a completely different directory

Before you start

• The Pods guide, particularly the multi-container section.
• A cluster with at least two worker nodes, for the last step.
• SSH with sudo on a worker node, to read the hostPath directory from outside Kubernetes.

1. 1

   emptyDir is how two containers share a filesystem

2. 2

   Delete the Pod and the emptyDir goes with it

3. 3

   hostPath writes to the node, and you can prove it

4. 4

   The same hostPath on another node is a different directory

Official sources

• Volumes
• emptyDir
• hostPath
• Ephemeral volumes
• Pod Security Standards
• Node-pressure eviction