What is /var/lib/containers used for when deploing OCI

Support
#1

Problem:
Tried following docs at Multi-Process Images - Pulp Project to setup Pulp in a container

The docs tell me to create a mount for /var/lib/containers, but I am confused what part of Pulp is using it.
I was expecting all pulp data to be in /var/lib/pulp (and /etc/pulp, for configs).

Expected outcome:
No confusion :slight_smile:

Pulpcore version:
Irrelevant

Pulp plugins installed and their versions:
Irrelevant

Operating system - distribution and version:
Irrelevant

Other relevant data:

#2

I found this in other section:

We do not bother to move /var/lib/containers because it is only ever used for temporary files by pulp_container, and may be used on the host for other purposes (like running podman).

Maybe this could be further clarified? or its just about finding this info?

#3

Having that info on the Multi-Process Images - Pulp Project would be cool, yeah.

But then, looking further, Single-Process Images - Pulp Project doesn’t mention those paths at all?

What happens if /var/lib/containers doesn’t exist when pulp_container is used? Katello deployments don’t have that folder, for example.

#4

The /var/lib/containers path is not directly used by pulp_container. In rootless environments, it seems like the nested podman can have permission errors: Nested container image builds and pushes are failing to start · Issue #540 · pulp/pulp-oci-images · GitHub.

pulp_container uses /var/lib/pulp/tmp/<pid>@<worker>/ as a temporary area (to keep cached layers, build context files, etc.) for the build machinery. This build process runs a podman build, and podman (not Pulp) may need access to /var/lib/containers/storage (graphroot), which can cause errors.

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#5

@hyagi but why would podman/buildah/skopeo be executed inside the running pulp container (besides CI which might prepare containers to push or something)?

reads further

oooh, you can upload a containerfile and pulp_container will build it FOR us? TIL!

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#6

oooh, you can upload a containerfile and pulp_container will build it FOR us?

Yep! It is still in tech preview, but you can upload the Containerfile in the build request:

http --form POST ${BASE_ADDR}${CONTAINER_REPO}'build_image/' "containerfile@./Containerfile" 
build_context=${FILE_REPO}versions/1/

or, if the Containerfile is already stored in pulp_file, you just need to pass its name (with the file repository_version):

http --form POST ${BASE_ADDR}${CONTAINER_REPO}'build_image/' containerfile_name=MyContainerfile build_context=${FILE_REPO}versions/2/

and pulp_container will build (using podman build) the container image.

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