NAME

Container::Buildah - wrapper around containers/buildah tool for multi-stage builds of OCI/Docker-compatible Linux containers

VERSION

version 0.2.0

SYNOPSIS

    use <Container::Buildah>;

        # configure container build stages
        Container::Buildah::init_config(
                basename => "swpkg",
                base_image => 'docker://docker.io/alpine:[% alpine_version %]',
                stages => {
                        build => {
                                from => "[% base_image %]",
                                func_exec => \&stage_build,
                                produces => [qw(/opt/swpkg-apk)],
                        },
                        runtime => {
                                from => "[% base_image %]",
                                consumes => [qw(build)],
                                func_exec => \&stage_runtime,
                                commit => ["[% basename %]:[% swpkg_version %]", "[% basename %]:latest"],
                        }
                },
                swpkg_version => "9.16.4",
        );

        # functions to run each stage inside their container namespaces
        sub stage_build {
                my $stage = shift;
                # code to run inside the namespace of the build container
                # set up build container and copy newly-built Alpine APK packages into /opt/swpkg-apk ...
                # See Container::Buildah:Stage for the object passed to each stage function
        }
        sub stage_runtime {
                my $stage = shift;
                # code to run inside the namespace of the runtime container
                # set up runtime container including installing Alpine APK packages from /opt/swpkg-apk ...
                # See Container::Buildah:Stage for the object passed to each stage function
        }

        # Container::Buildah::main serves as script mainline including processing command-line arguments
        Container::Buildah::main(); # run all the container stages

DESCRIPTION

Container::Buildah allows Perl scripts to build OCI/Docker-compatible container images using the Open Source buildah command. Containers may be pipelined so the product of a build stage is consumed by one or more others.

The Container::Buildah module grew out of a wrapper script to run code inside the user namespace of a container under construction. That remains the core of its purpose. It simplifies rootless builds of containers.

Container::Buildah may be used to write a script to configure container build stages. The configuration of each build stage contains a reference to a callback function which will run inside the user namespace of the container in order to build it. The function is analagous to a Dockerfile, except that it's programmable with access to computation and the system.

The buildah command has subcommands equivalent to Dockerfile directives. For each stage of a container build, Container::Buildah creates a Container::Buildah::Stage object and passes it to the callback function for that stage. There are wrapper methods in Container::Buildah::Stage for subcommands of buildah which take a container name as a parameter.

The Container::Buildah module has one singleton instance per program. It contains configuration data for a container build process. The data is similar to what would be in a Dockerfile, except this module makes it scriptable.

METHODS

debug

Prints a list of strings to STDERR, if debugging is at the specified level. If the first argument is a HASH reference, it is used for key/value parameters. The recognized parameters are =over =item "name" for the name of the caller function, defaults to the name from the Perl call stack =item "level" for the minimum debugging level to print the message =item "label" for an additional label string to enclose in brackets, such as a container name =back

get_config

required_config

get_debug

Return integer value of debug level

set_debug

Take an integer value parameter to set the debug level. A level of 0 means debugging is turned off. The default is 0.

prog

buildah

tag

main

FUNCTIONS

init_config

status

prints a list of strings to STDOUT

BUGS AND LIMITATIONS

Please report bugs via GitHub at https://github.com/ikluft/Container-Buildah/issues

Patches and enhancements may be submitted via a pull request at https://github.com/ikluft/Container-Buildah/pulls

AUTHOR

Ian Kluft <https://github.com/ikluft>

COPYRIGHT AND LICENSE

This software is Copyright (c) 2020 by Ian Kluft.

This is free software, licensed under:

  The Apache License, Version 2.0, January 2004

cpanm Container::Buildah

perl -MCPAN -e shell
install Container::Buildah