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vpsAdminOS Image Build Scripts

Deprecation notice

This repository has been merged into vpsAdminOS:

https://github.com/vpsfreecz/vpsadminos

Further development will take place there.

About

This is a collection of scripts used to build and test container images, which are then used by vpsAdminOS when creating new containers. Container image is a tarball with configuration and filesystems, see the specification. More information about container images can be found in the documentation.

Building images

Images can be built within vpsAdminOS using osctl-image. osctl-image needs the build scripts in its current working directory.

git clone git@github.com:vpsfreecz/vpsadminos-image-build-scripts.git
cd vpsadminos-image-build-scripts

Usage:

osctl-image --help
NAME
    osctl-image - Build, test and deploy vpsAdminOS images

SYNOPSIS
    osctl-image [global options] command [command options] [arguments...]

VERSION
    19.03.0

GLOBAL OPTIONS
    --help    - Show this message
    --version - Display the program version

COMMANDS
    build       - Build image
    ct          - Manage build and test containers
    deploy      - Build image, test it and deploy to repository
    help        - Shows a list of commands or help for one command
    instantiate - Build the image and use it in a container
    ls          - List available images
    test        - Test image

To get a list of available images, use:

osctl-image ls

osctl-image requires a dedicated ZFS dataset which is used for building images. The dataset should not have any data or subdatasets that you care about.

zfs create tank/image-builds

To build an image, use command osclt-image build, e.g.:

osctl-image build --build-dataset tank/image-builds alpine-3.9

Tests can be run as:

osctl-image test --build-dataset tank/image-builds alpine-3.9

Images can be also tested manually in container. Use command osctl-image instantiate to create one:

osctl-image instantiate --build-dataset tank/image-builds alpine-3.9

Managed containers can be listed using command osctl-image ct ls and cleaned up using osctl-image ct del. See man osctl-image(8) for more information.

Contributing build scripts

Target images are represented by directories in images/. Every image directory has to contain two files: config.sh and build.sh. config.sh is used to set variables such as distribution name, version and so on, see below. This information is used by osctl-image. build.sh is called to actually build the image.

Shared code can be placed into include/, follow the existing naming scheme.

How does it work

The image build script needs to prepare the distribution's root filesystem in directory stored in variable $INSTALL. The script can download arbitrary assets into directory $DOWNLOAD. When the script finishes, the $INSTALL directory should contain the root filesystem, i.e. directories like bin, usr, var, home and so on.

The build script can generate configuration script, that will be executed as chrooted within the $INSTALL directory. Function configure-append is used to append chunks of the configuration script and run-configure will chroot to the $INSTALL directory and run it. This is where you can use the distribution's package manager and other programs.

For example, to create a Debian image, you would use debootstrap to download the base root file system, then use the configuration script to install additional packages and configure the services.

Image name and variables

The image has to define the following variables in config.sh:

  • BUILDER - name of a builder that the image has to be built in, see below

Additional variables are optional:

  • DISTNAME, e.g. debian, ubuntu
  • RELVER, e.g. 9 for Debian or 16.04 for Ubuntu
  • ARCH (defaults to x86_64)
  • VENDOR (defaults to vpsadminos)
  • VARIANT (defaults to minimal)

If not set, osctl-image tries to extract the values from the image name, which should be in the following form:

<DISTNAME>[-RELVER[-ARCH[-VENDOR[-VARIANT]]]]

Builders

Images are built in builders, which are vpsAdminOS containers. Builders are defined in directory builders/ by two files: config.sh and setup.sh.

config.sh is similar to image configs, it specifies what distribution and version should the builder be created from. Builders are simply containers created from pre-existing images available in vpsAdminOS repository at https://images.vpsadminos.org, or whatever repository you have configured on your system.

setup.sh is run within the builder container after it is created. This script should installed whatever packages are needed to build images that use this builder.