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> I wrote undocker[1], which converts a docker "container" to a rootfs tarball

I thought a "container" (or, more precisely, a "container image"; or even more precisely, a "container image layer") is a tarball?

I've been creating multi-layer container images using `tar` (plus `sha256sum` and `jq` for the corresponding JSON "manifests"), and it works fine e.g. on AWS ECS.

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A tarball of tarballs, layered using barely documented rules (e.g. you can add a directory, remove it on upper layer, and re-add something else on top).

Constructing them is easier than unpacking. :)

Ah, so you're re-creating the results of overlay-mounting the layers?

I'm definitely ignorant of the exact rules for those; I only use them to split up large images into a "mostly static" layer (e.g. dependencies, which may be large) and a "subject to change" layer (i.e. our code, which will be different for each version)

Can you detail further? - Personally, this seems like insanity so I'm curious what lead you down this path instead of using the more common tools like docker compose or buildah.

> instead of using the more common tools like docker compose or buildah

How are those tools "more common" than GNU tar?

> I'm curious what lead you down this path

I had an executable; I wanted to run it on ECS; so I ran the `tar` command. Pretty simple really :)

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