tmpfs noswap support

[bplaxco]

Feature request description

Would like the ability to create noswap tmpfs mounts through --mount so that I can ensure sensitive variable runtime data is never written to disk.

(Also this might be a potentially useful tweak/option to add to the secret feature in podman, but I haven't dug into that as much since that appears to be for static secrets. I still wanted to mention that here since I read something that indicated those are also stored on tmpfs volumes and didn't see matches for noswap in any of the repos here.)

Suggest potential solution

Support a tmpfs-noswap flag that would be similar to passing -o noswap to mount for a tmpfs.

Have you considered any alternatives?

I have considered doing something like:

$ podman run -it --rm --cap-add=sys_admin registry.redhat.io/ubi8:latest
mkdir foo && mount -t ramfs -o size=10M ramfs ./foo

But id rather not add extra caps in. I also considered doing a noswap tmpfs on the host and mounting that into the container.

Additional context

This isn't urgent at all, and I figured I'd call this and the potential use case out in the secret feature here in case it's useful for other folks as well.

Thanks for all the great work folks! ^_^

[bplaxco]

@rhatdan thanks for the quick response on that! I appreciate it ^_^