To implement volume.emptyDir in Kubernetes config for the "play kube" command

[ratermir]

FEATURE REQUEST

It looks like Podman Currenty supports only host mounted volumes in kubernetes deployment yaml. If I try to define something like this:

      volumes:
        - name: temp-vol-shared
          emptyDir: {}

I get message that only hostPath is currently supported.

It would be really helpful tu support this, especially with "in-memory" storage.

I use OpenSuSE Leap, where the latest podman version is 2.2, but I didn't find this feature in release notes for all 3.x releases, so I suppose it still is not implemented.

[rhatdan]

@umohnani8 @haircommander What is an emtryDir volume from a Podman perspective

[ratermir]

Normal Kubernetes "emptyDir" is a directory, which is initially (after the POD starts) empty, can be mounted into containers like normal volume, and is destroyed after the POD stops. Its goal is data exchange among containers inside the POD, and temporary storage, where we needn't care about its cleaning.

I thing there is no exact equivalent in Podman, it can be something like temporary volume or so (i.e. create volume somewhere inside POD's filesystem space), and delete it after POD ends. I don't know Podman "guts" to tell how complicate it would be.

Additional option to emptyDir is "in memory volume" - it is an additional configuration item under emptyDir K8S YAML config, which tells that the temporary volume is created in memory; the rest is the same as before..

Generally it is really useful for data exchange among containers inside the POD and widely used in Kubernetes deployments. Even if it can be replaced with temporary directory mounted into POD (from local filesystem) and shell script which deletes it after POD stops, it is more complicated and far less comfortable.

[rhatdan]

We could do something with an overlay mount for a large temporary file system,
And a tmpfs for a one in memory.

@umohnani8 PTAL

[rhatdan]

@ratermir Interested in opening a PR for this.
We are already doing something like this with /dev/shm.

[ratermir]

Is there anything I can do for it? Note that I am not a go developer, but Kubernetes user.

[rhatdan]

No problem, I am sure someone will pick this up, since it seems like a fun project.

[github-actions]

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[rhatdan]

@umohnani8 were you able to look at this?

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[Sadin]

Is this still on the table? Would like to take a stab at it and start helping podman

[mheon]

Feel free to take a stab at it!

[Sadin]

Got my dev environment setup, reading up on

https://kubernetes.io/docs/concepts/storage/volumes/#emptydir
https://www.kernel.org/doc/html/latest/filesystems/tmpfs.html

Where might I find more information on how podman is already using /dev/shm?

[1player]

Any update?

[rhatdan]

@ashley-cui @umohnani8 @mheon @vrothberg can we get an intern to work on this, or someone else take it.

[vrothberg]

@ashley-cui @umohnani8 @mheon @vrothberg can we get an intern to work on this, or someone else take it.

I suggest moving Kube-related issues up the priority list as discussed yesterday during planning. Probably worth creating an epic for it.

[github-actions]

A friendly reminder that this issue had no activity for 30 days.

[rhatdan]

@umohnani8 any progress on this?

[umohnani8]

yup on it, will have a PR this week.