www/content/blog/kubernetes/dev-shm.md

title	description	date	tags
How to increase /dev/shm size on kubernetes	the equivalent to docker's shm-size flag	2024-10-02	kubernetes

Introduction

Today I had to find a way to increase the size of the shared memory filesystem offered to containers for a specific workload. /dev/shm is a Linux specific tmpfs filesystem that some applications use for inter process communications. The defaults size of this filesystem on kubernetes nodes is 64MiB.

Docker has a --shm-size 1g flag to specify that. Though kubernetes does not offer a direct equivalent, we can replicate this with volumes.

Configuration in pod specification

Here are the relevant sections of the spec we need to set:

spec:
  template:
    spec:
      container:
        volume_mount:
          mount_path        = "/dev/shm"
          name              = "dev-shm"
          read_only         = false
      volume:
        empty_dir:
          medium     = "Memory"
          size_limit = "1Gi"
        name = "dev-shm"

Conclusion

Well it works!