Lab 8.0 - Composing containers with Buildah | Red Hat

Table of Contents

Building from Universal Base Images
Build using Docker (BuD)

This module will introduce Buildah, a command line tool for building Open Container Initiative compatible container images. Buildah is easy to incorporate into scripts and build pipelines, and best of all, it doesn’t require a running container daemon to build its image. You can read more about Buildah at the buildah.io web site. Also, have a look at the buildah chapter in the RHEL 8 documentation.

Building from Universal Base Images

Below are the basic steps for building a container image from a UBI. No Dockerfile needed. Give it a try! Get creative, the lab is almost finished!

buildah from --name=myapp registry.access.redhat.com/ubi8/ubi
buildah run myapp -- dnf -y install python3

Now, add the rest of the container configuration:

echo "The container is working." > index.html
buildah copy myapp index.html /
buildah config --cmd 'python3 -m http.server' myapp
buildah config --author "me_at_myorg_dot_com @twitter-handle" --label name=myapp myapp
buildah commit myapp myapp
podman run -d --name=test -p8000:8000 localhost/myapp

Use curl to test that everything worked.

curl localhost:8000

The container is working.

Clean up

podman rm -f test

284681fbc26f52dfdfa4c5a3b1680635984f9f1d2c1a97967ebe637297a646e5

Build using Docker (BuD)

Create the following Dockerfile

cat > Dockerfile <<EOF
FROM registry.access.redhat.com/ubi8/ubi
LABEL description="Minimal python web server" maintainer="yourname@mail.net"
RUN dnf -y update; dnf -y clean all
RUN dnf -y install python3 --setopt install_weak_deps=false; dnf -y clean all
RUN echo "The python http.server module is running." > /index.html
EXPOSE 8000
CMD [ "/usr/bin/python3",  "-m", "http.server" ]
EOF

Create a new container image from Dockerfile.

buildah bud -t buildahbuddemo Dockerfile

STEP 1: FROM registry.access.redhat.com/ubi8/ubi
STEP 2: LABEL description="Minimal python web server" maintainer="yourname@mail.net"
...
...
...
STEP 8: COMMIT buildahbuddemo
Getting image source signatures
Copying blob d3ada5af5602 skipped: already exists
Copying blob 668db11eda93 skipped: already exists
Copying blob 345745e99612 done
Copying config a605153218 done
Writing manifest to image destination
Storing signatures
a60515321805733cdd83216ad249fb857cdd2389ead39b2fc59446b1650e78fc
a60515321805733cdd83216ad249fb857cdd2389ead39b2fc59446b1650e78fc

Inspect the container image meta data

buildah inspect --type image buildahbuddemo

Confirm the build and run the new container.

podman images

REPOSITORY                                            TAG      IMAGE ID       CREATED         SIZE
localhost/buildahbuddemo                              latest   a60515321805   2 minutes ago   257 MB

podman run -it -d --name=test -p8000:8000 localhost/buildahbuddemo

2abd1c20b89eac06a20e407e88689ee1067e7d36e27332fb21a143bc33246400

Use curl to test that everything worked.

curl localhost:8000

The python http.server module is running.

Clean up

podman rm -f test

284681fbc26f52dfdfa4c5a3b1680635984f9f1d2c1a97967ebe637297a646e5

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