12. ROS2 Metapackage Introduction

Note: The accompanying reference video uses the ROS Humble version, for reference only

1. Metapackage Overview

Completing a systematic function may involve multiple packages. For example, if you implement a robot navigation module, that module may include different sub-packages such as mapping, localization, path planning, etc. So when a caller wants to install that module, do they need to install each package one by one?

Obviously, installing packages one by one is inefficient. In ROS2, a method is provided to combine different packages into a single package. When installing a certain function module, you can directly use the packaged package. This package is called a metapackage.

MetaPackage is a concept from Linux's file management system. It is a virtual package in ROS2 that contains no substantial content, but it depends on other software packages. Through this method, other packages can be combined. We can think of it as a book's table of contents, telling us which sub-packages are in this package collection and where to download them.

For example: When installing ros2 with the sudo apt install ros-jazzy-desktop command, a metapackage is used. This metapackage depends on other packages in ROS2, and installing it will also install its dependencies.

Classic metapackage example: navigation2

• navigation2 GitHub repository: GitHub - ros-navigation/navigation2: ROS 2 Navigation Framework and System

2. Purpose

Facilitate user installation. We only need this one package to organize and install other related software packages together.

3. Implementation

1. Create a new package:

ros2 pkg create pkg_metapackage

2. Modify the package.xml file and add packages that are depended on during execution:

​x
<?xml version="1.0"?>
<?xml-model href="http://download.ros.org/schema/package_format3.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
<package format="3">
  <name>pkg_metapackage</name>
  <version>0.0.0</version>
  <description>TODO: Package description</description>
  <maintainer email="1461190907@qq.com">root</maintainer>
  <license>TODO: License declaration</license>

  <buildtool_depend>ament_cmake</buildtool_depend>

  <exec_depend>pkg_interfaces</exec_depend>
  <exec_depend>pkg_helloworld_py</exec_depend>
  <exec_depend>pkg_topic</exec_depend>
  <exec_depend>pkg_service</exec_depend>
  <exec_depend>pkg_action</exec_depend>
  <exec_depend>pkg_param</exec_depend>

  <test_depend>ament_lint_auto</test_depend>
  <test_depend>ament_lint_common</test_depend>

  <export>
    <build_type>ament_cmake</build_type>
  </export>
</package>

3. CMakeLists.txt content is as follows:

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cmake_minimum_required(VERSION 3.5)
project(pkg_metapackage)

if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  add_compile_options(-Wall -Wextra -Wpedantic)
endif()

find_package(ament_cmake REQUIRED)

ament_package()

4. Build metapackage:

• There will be no actual executable files:

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colcon build --packages-select pkg_metapackage