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Installing gazebo_ros_pkgs (ROS 2)

Introduction

The set of ROS 2 packages for interfacing with Gazebo are contained within a meta package named gazebo_ros_pkgs. See ROS 2 Overview for background information before continuing here.

The packages support ROS 2 Crystal and Gazebo 9, and can be installed from debian packages or from source.

Prerequisites

You should understand the basic concepts of ROS 2 and have gone through some ROS 2 Tutorials.

Install ROS 2

ROS2 can be installed either through binary installation or source installation, see the ROS 2 installation page. The current stable distribution is Crystal.

Tip: Don't forget to source setup.bash script as instructed on the ROS installation page. The exact command will be different according to the installation method.

Install Gazebo

You can install Gazebo either from source or from pre-build packages. See Install Gazebo.

You should install Gazebo 9. If installing from source, be sure to build the gazebo9 branch.

Tip: You may need to source Gazebo's setup file if you're having difficulty finding plugins and other resources. For example: source /usr/share/gazebo/setup.sh.

Install gazebo_ros_pkgs

Follow either the instructions to install from debian packages, or the instructions to install from source.

Install from debian packages (on Ubuntu)

Assuming you already have some Crystal debian packages installed, install gazebo_ros_pkgs as follows:

sudo apt install ros-crystal-gazebo-ros-pkgs

Install from source (on Ubuntu)

If you are an active developer setting up to contribute to the code base, it is advisable to have the source installation, as it provides more access and control over the workflow.

Tip: These instructions require the use of the colcon build tool, which is the standard tool used in ROS 2.

You'll need to choose the branch of gazebo_ros_pkgs according to the ROS 2 version you're using. The currently supported branches are:

crystal: works with Crystal debians or Crystal's ros2.repos.
ros2: points to the next unreleased ROS 2 turtle, currently Dashing. It works with the master ros2.repos.

The following setup assumes installation with ros2 branch of gazebo_ros_pkgs.

Make sure git is installed on your Ubuntu machine:
```
sudo apt install git
```
Create a directory for the colcon workspace and move into it:
```
mkdir -p ~/ws/src
```
Copy this file, that gets gazebo_ros_pkgs and additional packages needed:
```
cd ~/ws
wget https://bitbucket.org/api/2.0/snippets/chapulina/geRKyA/f02dcd15c2c3b83b2d6aac00afe281162800da74/files/ros2.yaml
```
Note: The version tag in the yaml file indicates the branch we are checking out for a particular repository e.g. version: ros2 checks out the ros2 branch.
Get the packages into the src directory
```
cd ~/ws
vcs import src < ros2.yaml
```

Install all dependencies:

cd ~/ws
rosdep install --from-paths src --ignore-src -r -y

Then build all the packages:
```
cd ~/ws
colcon build --symlink-install
```
Note: Before building this ensure that the ROS 2 environment is sourced correctly.
If you've had any problems building, be sure to ask for help at answers.gazebosim.org.
Be sure to source this workspace's install setup for every new terminal you open:
```
source ~/ws/install/setup.bash
```
Tip: You can make this be automatically sourced for every new terminal by running this once: echo "source ~/ws/install/setup.bash" >> ~/.bashrc

Testing Gazebo and ROS 2 integration

Assuming your ROS 2 and Gazebo environments have been properly setup and built, you should now be able to load Gazebo worlds which contain ROS 2 plugins, and to insert models at runtime which have ROS 2 plugins in them.

Gazebo ROS packages provides several demo worlds for you to get a quick start with the plugins. The demo worlds can be found here, and are installed by default under /opt/ros/<distro>/share/gazebo_plugins/worlds/.

Each world file comes with instructions at the top with some example commands that you can run to test its functionality, be sure to check that out!

Let's try loading one of them now!

Open a new terminal
Source ROS 2 as instructed when you installed ROS 2.

Make sure you have some core tools installed:

sudo apt install ros-crystal-ros-core ros-crystal-geometry2

If you installed gazebo_ros_pkgs from source, source the workspace:
```
. ~/ws/install/setup.bash
```

Load the differential drive world with Gazebo:

gazebo --verbose /opt/ros/crystal/share/gazebo_plugins/worlds/gazebo_ros_diff_drive_demo.world

The Gazebo GUI should appear with a simple vehicle:
On a new terminal (this is the 2nd one), run the following command to take a look at the world file.
```
gedit /opt/ros/crystal/share/gazebo_plugins/worlds/gazebo_ros_diff_drive_demo.world
```
See how the block on the top has a few example commands? Let's open a 3rd terminal and, again, source ROS 2 and gazebo_ros_pkgs as described above.

Then run one of the commands, for example:

ros2 topic pub /demo/cmd_demo geometry_msgs/Twist '{linear: {x: 1.0}}' -1

You'll see the vehicle moving forward:
Try out the other commands listed on the file, and try mofidying their values to get a feeling of how things work. Also try out other demo worlds!