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Managing System dependencies

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System Dependencies

ROS packages sometimes require external libraries and tools that must be provided by the operating system. These required libraries and tools are commonly referred to as system dependencies. In some cases these system dependencies are not installed by default. ROS provides a simple tool, rosdep, that is used to download and install system dependencies.

ROS packages must declare that they need these system dependencies in the package manifest. Let's look at the manifest for the turtlesim package:

$ roscd turtlesim

Then,

$ cat package.xml

$ cat manifest.xml

rosdep

rosdep is a tool you can use to install system dependencies required by ROS packages.

Usage:

rosdep install [package]

Download and install the system dependencies for turtlesim:

$ rosdep install turtlesim

If you've been following along with the tutorials, it's likely that this is the first time you've used rosdep. When you run this command, you'll get an error message:

• ERROR: your rosdep installation has not been initialized yet.  Please run:
  
      sudo rosdep init
      rosdep update

Just run those two commands and then try to install turtlesim's dependencies again.

If you installed using binaries you will see:

• All required rosdeps installed successfully

Otherwise you will see the output of installing the dependencies of turtlesim:

• #!/usr/bin/bash
  
  set -o errexit
  set -o verbose
  
  
  if [ ! -f /opt/ros/lib/libboost_date_time-gcc42-mt*-1_37.a ] ; then
    mkdir -p ~/ros/ros-deps
    cd ~/ros/ros-deps
    wget --tries=10 http://pr.willowgarage.com/downloads/boost_1_37_0.tar.gz
    tar xzf boost_1_37_0.tar.gz
    cd boost_1_37_0
    ./configure --prefix=/opt/ros
    make
    sudo make install
  fi
  
  
  if [ ! -f /opt/ros/lib/liblog4cxx.so.10 ] ; then
    mkdir -p ~/ros/ros-deps
    cd ~/ros/ros-deps
    wget --tries=10 http://pr.willowgarage.com/downloads/apache-log4cxx-0.10.0-wg_patched.tar.gz
    tar xzf apache-log4cxx-0.10.0-wg_patched.tar.gz
    cd apache-log4cxx-0.10.0
    ./configure --prefix=/opt/ros
    make
    sudo make install
  fi

rosdep runs the bash script above and exits when complete.

rosdistro/rosdep

While rosdep is the client tool, the reference is provided by rosdep rules, stored online in ros/rosdistro/rosdep on github.

When doing

$ rosdep update

rosdep actually retrieves the rules from the rosdistro github repository.

• As of version 0.14.0 rosdep update will only fetch ROS package names for non-EOL ROS distributions. If you are still using an EOL ROS distribution (which you probably shouldn't) you can pass the argument --include-eol-distros to also fetch the ROS package names of those.

These rules are used when a dependency is listed that doesn't match the name of a ROS package built on the buildfarm. Then rosdep checks if there exists a rule to resolve it for the proper platform and package manager you are using.

When creating a new package, you might need to declare new system dependencies to the rosdep rules if they are not there yet. Just edit the file, add the dependency needed (following a strict alphabetical order and a similar structure as the other dependencies already registered) and send a pull request.

After that pull request has been merged, you need to run :

$ rosdep update

and now that dependency will be resolved by rosdep.

You can test it with :

$ rosdep resolve my_dependency_name

The output should be something like :

#apt
my-dependency-name

where the first line is the package manager chosen for installing this dependency, and the second line is the actual name for that dependency on your current platform.