= Installing from source =

Install from source requires that you download and compile the source code on your own. ROS Noetic supports Ubuntu Focal and Debian Buster, but other platforms are possible. The target platforms are defined in [[http://www.ros.org/reps/rep-0003.html|REP 3]]

<<TOC(3)>>

== Prerequisites ==

=== Installing bootstrap dependencies ===

Install bootstrap dependencies (Ubuntu):

These tools are used to facilitate the download and management of ROS packages and their dependencies, among other things.

'''Ubuntu or Debian:'''

 {{{
$ sudo apt-get install python3-rosdep python3-rosinstall-generator python3-vcstools python3-vcstool build-essential
}}}

 {{{#!wiki blue/solid
If you have trouble installing the packages in the command above, make sure you have added the packages.ros.org debian repository to your apt source lists as described starting here: [[noetic/Installation/Ubuntu#Installation.2BAC8-Ubuntu.2BAC8-Sources.Setup_your_sources.list]]
}}}

'''Fedora:'''

 {{{
$ sudo dnf install gcc-c++ python3-rosdep python3-rosinstall_generator python3-vcstool @buildsys-build
}}}

 {{{#!wiki blue/solid
Some packages used in ROS are not currently available in the Fedora RPM repositories. Most of the other packages are available in RPM Fusion. See [[http://rpmfusion.org/Configuration#Command_Line_Setup_using_rpm|RPM Fusion Command Line Setup]].
}}}

'''Generic (pip):'''

 If you are using a non-Debian system you need to make sure that you have all build tools (compiler, CMake, etc.) installed. You can install all ROS Python tools via PIP:

 {{{
$ sudo pip3 install -U rosdep rosinstall_generator vcstool
}}}

 If there are errors with this or the rosdep step below, your system's version of pip may be out-of-date. Use your system's package management to update it, or use it to update itself:

 {{{
$ sudo pip3 install --upgrade setuptools
}}}

 {{{#!wiki blue/solid
Note that on many platforms such as OSX you may want to install the above packages and use ROS inside a virtualenv so as to make sure not to collide with system dependencies.
}}}

=== Initializing rosdep ===

{{{
$ sudo rosdep init
$ rosdep update
}}}


== Installation ==

Start by building the core ROS packages.

=== Create a catkin Workspace ===

In order to build the core packages, you will need a catkin workspace. Create one now:

 {{{
$ mkdir ~/ros_catkin_ws
$ cd ~/ros_catkin_ws
}}}

Next we will want to download the source code for ROS packages so we can build them. We will use [[vcstool]] for this. For the purpose of this guide, we'll assume you'd like to build all of ''Desktop''.

 {{{
$ rosinstall_generator desktop --rosdistro noetic --deps --tar > noetic-desktop.rosinstall
$ mkdir ./src
$ vcs import --input noetic-desktop.rosinstall ./src
}}}

This will download all of the source code for packages part of ''Desktop'' into the `~/ros_catkin_ws/src` directory. The command will take a few minutes to download everything.

{{{#!wiki blue/solid
Looking for something other than ''Desktop''? More variants are defined in [[https://www.ros.org/reps/rep-0150.html|REP 150]] such as `desktop_full`, `robot`, `perception`, etc. Just change the package path above from `desktop` to the one you want.
}}}

==== Resolving Dependencies ====

Before you can build your catkin workspace you need to make sure that you have all the system dependencies on your platform. We use the `rosdep` tool for this:

 {{{
$ rosdep install --from-paths ./src --ignore-packages-from-source --rosdistro noetic -y
}}}

`rosdep` looks at all the packages in the `src` directory and tries to find and install their dependencies on your platform. After a while (and maybe some prompts for your password) rosdep will finish installing system dependencies and you can continue.


==== Building the catkin Workspace ====

By now you have a workspace with all of the source code, and all required system dependencies have been installed. Now it's time to build the code. ROS 1 packages use CMake; however, calling `cmake` by hand on all the packages by hand would be tedious. There are tools we can use to build all the packages in the right order. The tool we'll use is `catkin_make_isolated`.

{{{#!wiki blue/solid
`catkin_make_isolated` isn't the only tool we could use. There are other tools that would work, like [[catkin/commands/catkin_make|catkin_make]] or [[https://catkin-tools.readthedocs.io/en/latest/|catkin_tools]] (which has a command line executable called `catkin`), or [[https://colcon.readthedocs.io/en/released/|colcon]]. Some of those might be better for your use case, but we'll use `catkin_make_isolated` here since that's what the ROS buildfarm uses.
}}}

This command will build everything in the workspace. It may take a while. The command is running `catkin_make_isolated` command from the source folder because it has not been installed yet. Once installed it can be called using just `catkin_make_isolated`.

 {{{
$ ./src/catkin/bin/catkin_make_isolated --install -DCMAKE_BUILD_TYPE=Release
}}}

{{{#!wiki blue/solid
'''Note:''' If you see an error relating to the EMPY module being missing you may be building using Python 2 rather than Python 3.  To ensure you are using the latter, append the the following to the command above. If you have Python 3 installed elsewhere, update the path accordingly.

`-DPYTHON_EXECUTABLE=/usr/bin/python3`
}}}

{{{#!wiki blue/solid
'''Note:''' Want debug symbols? You might want to select a different [[https://cmake.org/cmake/help/v3.7/variable/CMAKE_BUILD_TYPE.html|CMake build type]].
}}}

When the above command finishes, it will have installed everything into `~/ros_catkin_ws/install_isolated`. If you would like to install somewhere else then add `--install-space path/to/somewhere/else` to the `catkin_make_isolated` call.

For usage on a robot without Ubuntu, it is recommended to install compiled code into `/opt/ros/noetic` just as the Ubuntu packages would do. Of course, don't do this in Ubuntu, as the packages would collide with apt-get packages.

Now the packages should have been installed to `~/ros_catkin_ws/install_isolated` or to wherever you specified with the `--install-space` argument. If you look in that directory you will see that a `setup.bash` file have been generated. To utilize the things installed there simply source that file like so:

 {{{
$ source ~/ros_catkin_ws/install_isolated/setup.bash
}}}


== Maintaining a Source Checkout ==

If we want to keep our source checkout up to date, you will have to periodically update your rosinstall file, download the latest sources, and rebuild the workspace.

=== Update your rosinstall file ===

To update your workspace, first move your existing rosinstall file so that it doesn't get overwritten, and generate an updated version

{{{
$ mv -i noetic-desktop.rosinstall noetic-desktop.rosinstall.old
$ rosinstall_generator desktop --rosdistro noetic --deps --tar > noetic-desktop.rosinstall
}}}

Then, compare the new rosinstall file to the old version to see which packages will be updated:

{{{
$ diff -u noetic-desktop.rosinstall noetic-desktop.rosinstall.old
}}}

=== Download the latest sources ===

If you're satisfied with these changes, incorporate the new rosinstall file into the workspace and update your workspace:

{{{
$ vcs import --input noetic-desktop.rosinstall ./src
}}}

=== Rebuild your workspace ===

Now that the workspace is up to date with the latest sources, rebuild it:

{{{
$ ./src/catkin/bin/catkin_make_isolated --install
}}}

{{{#!wiki blue/solid
If you specified the `--install-space` option when your workspace initially, you should specify it again when rebuilding your workspace
}}}

Once your workspace has been rebuilt, you should source the setup files again:

{{{
$ source ~/ros_catkin_ws/install_isolated/setup.bash
}}}