K8s: Is it possible to share folder between main container and sidecar?

Question

Trying to move my services to K8s. I am using helm for that and I want to describe my example with issue:

I need to move few services with own Apache`s. Yes, I understand, that this is working something like:

external traffic -> K8s nginx ingress -> pod Apache

But I cant change it for now. Apache is working with PHP. So, I have deployment for two images: php-fpm and Apache. And, in this case, I need to share php files from my first php-fpm container with Apache.

For now - I am using shared volumeMounts to copying files from one container to second (all date is preparing/compiling in the first container, php-fpm, during the build):

volumeMounts:
  - name: shared-files
    mountPath: /var/shared-www

And

lifecycle:
  postStart:
    exec:
      command: ["/bin/bash", "-c", "cp -r XXX /var/shared-www/"]

And it is working, but I would like to find solution to have one common point, like a symlink, to store files. I want to have ability to change files in one place and have changed files in both containers.

Is it possible?

PS I am using AWS EKS. And I don`t want to use network storage (like a EFS).

Answer 1

Why not use subPath as per official documentation:

it is useful to share one volume for multiple uses in a single pod. The volumeMounts.subPath property specifies a sub-path inside the referenced volume instead of its root.

So instead of running the command something like (to share XXX towards):

volumeMounts:
  - name: shared-files
    mountPath: /var/shared-www
    subpath: XXX

Update:

Kubernetes subpath vulnerability article