image-mode-basics: Containerfile should use Heredoc format

[benblasco]

As of Podman 4.9 we support the Heredoc format for containerfiles, so maybe it's worth moving to that. This means that the containerfile just has one RUN directive and therefore I believe it would reduce the number of layers, reducing the size of the container and the time it takes to build and transport.

Existing Containerfile

FROM registry.redhat.io/rhel9/rhel-bootc

ADD etc /etc

RUN dnf install -y httpd
RUN systemctl enable httpd

Proposed new Containerfile

FROM registry.redhat.io/rhel9/rhel-bootc

ADD etc /etc

RUN <<EOF
    dnf install -y httpd
    systemctl enable httpd
EOF

[benblasco]

Hello @nzwulfin, thoughts?

More reading on Heredoc here:
https://www.docker.com/blog/introduction-to-heredocs-in-dockerfiles/

[benblasco]

Note: Later when I added vim to the Containerfile the podman build command seemed not to pick it up. Will investigate further to see if it is a product issue.

[nzwulfin]

Generally I'm on board with this, very happy to see the support land. I did some local testing yesterday on this, it seems to have a few quirks I haven't worked out consistently. I'm going to keep testing and see if I can get consistent successes with a heredoc that works. Until then, I'll watch this.

[benblasco]

Looks like there's a bug based on my testing, so we will have to park it for now. I created a JIRA issue we can follow:
https://issues.redhat.com/browse/RHEL-50145