Container-Buildah

Container::Buildah Perl module for building OCI/Docker-compatible Linux containers

CPAN: https://metacpan.org/pod/Container::Buildah

NAME

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

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

status

prints a list of strings to STDERR, if debugging is set to level 1 or higher.

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.

main

prog

cmd

buildah

bud

containers

from

images

info

inspect

mount

pull

push

rename

rm

rmi

tag

umount

unshare

version

FUNCTIONS

init_config

FUNCTIONS AND METHODS