A base image is the starting image for a new container image. A Containerfile selects it with FROM, after which Podman adds files and commands to its rootfs. section 2.3.1
Podman pulls an existing base image from a registry into container storage, mounts it on a rootfs with copy-on-write storage such as OverlayFS, and uses it as the base layer for subsequent instructions. FROM scratch instead creates an empty rootfs for COPY-based construction. section 2.1 section 2.3.1
A base image establishes the starting point for:
- Installing packages or running other build commands with RUN, which commits each result as a new layer. section 2.3.1
- Copying application files into the image with COPY. section 2.3.1
- Defining the image’s later runtime behavior through directives such as CMD and ENTRYPOINT. section 2.3.1
Build an HTTP application image
Create a context directory containing index.html and a Containerfile with FROM ubi8/httpd-24 followed by COPY index.html /var/www/html/index.html. Run podman build -t quay.io/rhatdan/myimage ./myapp to commit and tag the resulting image. section 2.3.2
Table 2.6 Containerfile directives that update the image (view table figure)
Use the directive table to compare FROM with COPY, RUN, and runtime configuration instructions. section 2.3.1
