Kameleon reads YAML files, named recipes, that describes how you will build your appliance. A recipe is a hierarchical structure of Section, Step, Microstep and Commands. Here is an overview of this structure:

`-- section
    `-- step
        `-- microstep
            `-- command

The recipe also contains a set of Global variables declaration and some imports such as Aliases and Checkpoint.

Here is an example of a recipe:

# vim: softtabstop=2 shiftwidth=2 expandtab fenc=utf-8 cc=81 tw=80
# DESCRIPTION: Base template for Kameleon appliance.
extend: ../steps/backend/$${backend}.yaml

# Loads some helpful aliases (this files are located in steps/aliases/ directory)
aliases: defaults.yaml

# Custom shell environement (this files are located in steps/env/ directory)
  - bashrc

# Global variables use by Kameleon engine and the steps
  ## Select backend for in context isolation
  backend: qemu

  ## User varibales : used by the recipe
  user_name: kameleon
  user_password: $${user_name}
  root_password: $${user_name}
  user_groups: sudo
  default_keyboard_layout: "us,fr,de"
  default_locales: POSIX C en_US fr_FR de_DE
  default_lang: en_US.UTF-8
  default_timezone: UTC
  appliance_tar_compression_level: "9"

  ## Initial rootfs archive built with kameleon
  ## See
  rootfs_archive_download_path: $${kameleon_cwd}/rootfs.tar.xz
  # rootfs options
  rootfs: $${kameleon_cwd}/rootfs

  # Distribution
  arch: x86_64
  hostname: kameleon-$${distrib}

  # output appliance options
  filesystem_type: ext4
  image_size: 10G
  image_disk: $${kameleon_cwd}/base_$${kameleon_recipe_name}
  # Allowed formats are: tar.gz, tar.bz2, tar.xz, tar.lzo, qcow, qcow2, qed, vdi, raw, vmdk
  appliance_formats: qcow2 tar.gz
  appliance_filename: "$${kameleon_cwd}/$${kameleon_recipe_name}"
  appliance_tar_excludes: >-
    ./etc/fstab ./root/.bash_history ./root/kameleon_workdir ./root/.ssh
    ./var/tmp/* ./tmp/* ./var/log/* ./dev/* ./proc/* ./run/*

  ## System variables. Required by kameleon engine
  # Include specific steps
    - $${distrib}/$${release}
    - $${distrib}

  # E.g: net.ifnames=0 console=tty0 console=ttyS0,115200n8
  kernel_args: "quiet net.ifnames=0 biosdevname=0"

  - "@base"

# Install and configuration steps
  # Install
  - upgrade_system
  - install_software:
    - packages: $${setup_packages}
  # Configuration
  - configure_system:
    - locales: $${default_locales}
    - lang: $${default_lang}
    - timezone: $${default_timezone}
  - configure_keyboard:
    # set to english keyboard use 'localectl list-keymaps' to see available list
    - layout: $${default_keyboard_layout}
  - configure_network
  - kameleon_customization
  - create_user:
    - name: $${user_name}
    - groups: $${user_groups}
    - password: $${user_name}
  - clean_system

  - "@base"


Each section is a group of steps. Currently, there are 3 sections:

This section contains the bootstrap of the new system and create the in context (see Context).
Installs and configures steps.
Exports the generated appliance in the desired format.

Step and microstep

Each step contains a list of microsteps itself containing a list of Commands written in one YAML file. To be found by Kameleon, this file must be named by the step name plus the YAML extension .yaml. For example the software_install.yaml step file looks like this:

# Software Install
- add_contribs_source:
  - exec_in: perl -pi -e "s/main$/main contrib non-free/" /etc/apt/sources.list
- update_repositories:
  - exec_in: apt-get -y --force-yes update
- upgrade_system:
  - exec_in: apt-get -y --force-yes dist-upgrade
- clean:
  - on_export_init:
    - exec_in: apt-get -y --force-yes autoclean
    - exec_in: apt-get -y --force-yes clean
    - exec_in: apt-get -y --force-yes autoremove
# default packages
- packages: "ntp sudo"
- install_extra_packages:
  - exec_in: apt-get -y --force-yes install $$packages

A step will be called like a function in the recipe. You should provide a set of local variables if needed by the step or to override default variables (see Variables). Optionally, you can select only some microsteps to execute. Here is an example of step call:

- software_install:
    - packages: "debian-keyring ntp zip unzip rsync sudo"
    - add_contribs_source
    - update_repositories
    - clean
    - install_extra_packages

Steps path

The steps are YAML formated files stored in the steps directory which is located in the same directory as the recipe. To enable a better recipe reuse and ease of write, the steps are stored by default in specific folders depending on the sections.

Kameleon is looking for the steps files using the include_steps list value, if it is set in the recipe (NOT mandatory). For example, if you are building an ubuntu based distribution you can use:

    - ubuntu
    - debian/wheezy
    - debian

It also searches uppermost within the current section folder. In the previous example, in the bootstrap section, the search paths are scanned in this order:



Kameleon is using preprocessed variables. You can define it with the YAML key/value syntax my_var: my_value.To access these variables, you have to use the two dollar ($$) prefix. Like in a Shell you can also use $${var_name} to include your variables in string like this my-$${variable_name}-templated. It is also possible to use nested variables like:

my_var: foo
my_nested_var: $${my_var}-bar

Be careful, in YAML you cannot mix dictionary and list on the same level. That’s why, in the global dictionary, you can define your variables as indicated in the example above but, in the recipe or the steps, you must prefix your variable with a - like this - my_var: foo.

Global variables

Global variables are defined in the global dictionary of the recipe. Kameleon use some global variables to enable the appliance build. See Context and Steps path for more details.

You can also override a variable using inheritance mechanism or CLI --global option with one or more key:values. For Example:

kameleon build --global my_package:'vim git' user_name:myself myrecipe.yaml

Or in your recipe:

  # kameleon is too long to type!
  user_name: myself

New in version 2.7.0.

You can even overload variable (adding content to existing value) using the same syntax as bash:

kameleon build --global setup_packages:'$${setup_packages} git emacs' myrecipe.yaml

Or in your recipe:

  # I need these tools
  setup_packages: $${setup_packages} git emacs

For more information about inheritance variable see here: Inheritance and variables

Step local variables

In the recipe, you can provide some variables when you call a step. This variable override the global and the default variables.

  - add_user:
    - name: foo
  - add_user:
    - name: bar

Step default variables

In the step file, you can define some default variables for your microsteps. Be careful, to avoid some mistakes, these variables can be overridden by the step local variables but not by the global ones. If this is the behavior you expected, just add a step local variable that can be assigned by the global variable value:

    foo: bar
    - my_step:
        - foo: $${foo}

Kameleon variables

It is possible to access some variables created by Kameleon from the recipe. They are used to contextualize the execution of a recipe in a given environment.

The recipe name (eg. my_debian8)
Directory where the recipe is located (eg. ~/recipes)
Directory the is watch by the cache mechanism: Each local file that is used during the build should be located here. See Data for more information.
Current recipe of Kameleon during the build (eg. ~/recipes/build/my_debian8)
Unique identifier of a Kameleon build. (eg. 33fb8999-bbd3-4bc5-badd-93983b14555d)
Shorter version of the identifier, basically the end of the uuid. (eg. 93983b14555d)
‘true’ if the user enabled the cache, otherwise ‘false’.


File that are stored in steps/data/ of your recipe, or of a recipe it extends, can be access with the built-in variable $${kameleon_data_dir}. The advantage of this mechanism over a simple copy from one context to an other is twofold:

  • All the artefact used to produce your recipe are stored inside you Kameleon workspace and the persistent cache is caching everything that is located on these directories.
  • You can override any artifacts inherited from a parent recipe by providing an other file that as the same name in the steps/data/ folder of the child recipe.


You MUST use this directory if you want to cache any data that is not coming from the web.

An example is better than long sentences, so here is an example:

By default, some Kameleon recipes gives you a .bashrc file that customize you prompt and add some aliases, but you have your own built-over-the-years bash configuration file and you want all your images to have it. To do so, just override the skel/.bashrc that is used by the kameleon_customization.yaml step in your data folder:

# where your recipe is:
mkdir -p steps/data/skel
cp ~/.bashrc steps/data/skel

And that’s it! When you will build your recipe all your aliases and pretty prompt colors will be there :)