I have an old image, may its name be B:latest. It has been built on top of another image, may its name be A:latest.
I have still the script that has been used for building. It is something like that:
conta=$(buildah from A:latest)
buildah run $conta ...
buildah copy $conta ...
...
buildah commit --rm $conta B:latest
A colleague has built the image years ago. I know, using always the tag latest was not a good choice, but this is another story.
My problem is now, I have to build a modified version of image B. I want to use a modified version of the old build script and build it on top of the old image A.
I have still a copy of image B. But the image A is no longer there. I can see only image B when I execute the command:
podman images --all
I can display the layers of the image by
podman image tree B:latest
So my hope was that I can add a new tag to the layer below the top layer and I could reuse this layer as a copy of image A, but it does not work. May the layer below the top layer have the id 11deadbeef00. I cannot see an image with this id with the command podman images --all, but it must still be contained somehow in image B. This was what I have tried:
podman image tag 11deadbeef00 newname
The error message was "Error: 11deadbeef00: image not known".
My question: Can I somehow access the layers below the top layer of a container image and make an image out of it that I can use independently?
With the caveat that this seems like a pretty clunky solution, you might be able to export the image to a directory:
podman image save B:latest |
tar --one-top-level=imageB -xf-
Edit the image metadata to remove the top layer:
$ vim manifests.json
...
$ vim $(jq -r jq .[0].Config manifest.json)
...
And then load the modified image back into podman:
tar -C imageB -cf- . | podman image load