Abstract:

Virt Maker is a command line tool for automating the creation of disk images heavily centered around libguestfs and quick turnaround.

It utilizes a straight-forward template system to define a specification for how an image needs to be built and uses snapshotting and rolling hashes to fast-forward over known good completed steps.

The thesis of this project is to provide a tool that can support rapid appliance image creation for virtualization environments where the boot volume is considered ephemeral and can be replaced quickly.

Template files will generate specs that define where an initial image comes from, what offline (or online in certain scenarios) steps need to run in order to configure the image, and once complete; how to store the resulting image.

Demo:

Building a new template with no previous cache:

$ virt-maker build -f examples/10-basic/template.yml

Running again with the same template:

Since the template has already been built, the second run will be instant. This is because all the steps have been cached and the final image is already complete.

[ FILE ] examples/10-basic/template.yml: Starting
[IMPORT] examples/10-basic/template.yml: {'image': 'centos-7.8', 'size': '6G'}
[ RUN  ] examples/10-basic/template.yml: yum clean all
[FIRSTB] examples/10-basic/template.yml: yum update -y
[HOSTNA] examples/10-basic/template.yml: 10-basic
[EXPORT] examples/10-basic/template.yml: {'path': 'images/10-basic.qcow2'}

Command Line Usage:

Overview

usage: virt-maker [-h] [-v] [-V] {build,cache,runners} ...

positional arguments:
  {build,cache,runners}
                        Actions

optional arguments:
  -h, --help            show this help message and exit
  -v, --verbose
  -V, --version         Show virt-maker version

Template Building

usage: virt-maker build [-h] -f BUILD_FILES [BUILD_FILES ...] [-p BUILD_PARAMS [BUILD_PARAMS ...]] [-F] [-X]

optional arguments:
  -h, --help            show this help message and exit
  -f BUILD_FILES [BUILD_FILES ...], --file BUILD_FILES [BUILD_FILES ...]
                        Path to template file(s)
  -p BUILD_PARAMS [BUILD_PARAMS ...], --param BUILD_PARAMS [BUILD_PARAMS ...]
                        Set or override template parameter
  -F, --force           Force build from scratch
  -X, --force-export    Force export to re-run

Cache Management

usage: virt-maker cache [-h] [-H] {clean,usage}

positional arguments:
  {clean,usage}

options:
  -h, --help            show this help message and exit
  -H, --human-readable  Output as human-readable values

Runner Information

usage: virt-maker runners [-h] {steps,importers,exporters}

positional arguments:
  {steps,importers,exporters}
                        Show the types of runners

optional arguments:
  -h, --help            show this help message and exit

Templates

Virt Maker uses a YAML file to define a template generating a build spec that consists of input parameters and the build specification template itself. The params section is used to define the input parameters and the spec section is used to define the build steps.

Basic template format

params:
  foo: bar
spec:
  import:
    some-import-runner:
      runner:
      args:
  steps:
    - some-step-runner:
        runner:
        args:
    - another-step-runner:
        more:
        args:
  export:
    some-export-runner:
      some-arg: '{{ foo }}'

Examples

See the Examples directory.

Installing

Prerequisites command line tools/packages

• scp
• virt-customize
• qemu-system-x86_64 or /usr/libexec/qemu-kvm
• virt-sysprep
• wget
• virt-resize
• truncate
• virt-builder
• cp or pv
• mv
• virt-sparsify
• words
• tesseract

Optional

• libguestfs-xfs
• libguestfs-zfs
• libguestfs-ufs
• libguestfs-rsync
• libguestfs-winsupport
• virt-win-reg
• virt-v2v
• xz
• gzip
• lz4c

Installing with pip

pip install .

Preparing a build host

EL Based

Basic Rocky Linux 9 Example

dnf install -y python-pip epel-release
pip install .
export LIBGUESTFS_BACKEND=direct
dnf install -y words qemu-kvm guestfs-tools wget xz lz4 pv tesseract

Test to see if it works

virt-maker build -f examples/10-basic/template.yml