Red Hat Summit Red Hat SummitSupportConsoleDevelopersStart a trialContact

Chapter 33. Shared Memory

33.1. Overview

There are two types of shared memory objects in Linux: System V and POSIX. The containers in a pod share the IPC namespace of the pod infrastructure container and so are able to share the System V shared memory objects. This document describes how they can also share POSIX shared memory objects.

33.2. POSIX Shared Memory

POSIX shared memory requires that a tmpfs be mounted at /dev/shm. The containers in a pod do not share their mount namespaces so we use volumes to provide the same /dev/shm into each container in a pod. The following example shows how to set up POSIX shared memory between two containers.

shared-memory.yaml

Copy to Clipboard Toggle word wrap 
---
apiVersion: v1
id: hello-openshift
kind: Pod
metadata:
  name: hello-openshift
  labels:
    name: hello-openshift
spec:
  volumes:
1 

    - name: dshm
      emptyDir:
        medium: Memory
  containers:
    - image: kubernetes/pause
      name: hello-container1
      ports:
        - containerPort: 8080
          hostPort: 6061
      volumeMounts:
2 

        - mountPath: /dev/shm
          name: dshm
    - image: kubernetes/pause
      name: hello-container2
      ports:
        - containerPort: 8081
          hostPort: 6062
      volumeMounts:
3 

        - mountPath: /dev/shm
          name: dshm

1
specifies the tmpfs volume dshm.
2
enables POSIX shared memory for hello-container1 via dshm.
3
enables POSIX shared memory for hello-container2 via dshm.

Create the pod using the shared-memory.yaml file:

Copy to Clipboard Toggle word wrap 
$ oc create -f shared-memory.yaml
Back to top
Red Hat logoGithubredditYoutubeTwitter

Learn

Try, buy, & sell

Communities

About Red Hat Documentation

We help Red Hat users innovate and achieve their goals with our products and services with content they can trust. Explore our recent updates.

Making open source more inclusive

Red Hat is committed to replacing problematic language in our code, documentation, and web properties. For more details, see the Red Hat Blog.

About Red Hat

We deliver hardened solutions that make it easier for enterprises to work across platforms and environments, from the core datacenter to the network edge.

Theme

© 2025 Red Hat, Inc.