You're reading the documentation for a version of ROS 2 that has reached its EOL (end-of-life), and is no longer officially supported. If you want up-to-date information, please have a look at Iron.
Troubleshooting techniques for installation are sorted by the platforms they apply to.
General troubleshooting techniques apply to all platforms.
In order to communicate successfully via DDS, the used network interface has to be multicast enabled. We’ve seen in past experiences that this might not necessarily be enabled by default (on Ubuntu or OSX) when using the loopback adapter. See the original issue or a conversation on ros-answers. You can verify that your current setup allows multicast with the ROS 2 tool:
In Terminal 1:
ros2 multicast receive
In Terminal 2:
ros2 multicast send
If the first command did not return a response similar to:
Received from xx.xxx.xxx.xx:43751: 'Hello World!'
then you will need to update your firewall configuration to allow multicast using ufw.
sudo ufw allow in proto udp to 18.104.22.168/4 sudo ufw allow in proto udp from 22.214.171.124/4
You can check if the multicast flag is enabled for your network interface using the
ifconfig tool and looking for
MULITCAST in the flags section:
eno1: flags=4163<...,MULTICAST> ...
Import failing without library present on the system
rclpy fails to be imported because the expected C extension libraries are not found.
If so, compare the libraries present in the directory with the one mentioned in the error message.
Assuming a file with a similar name exists (same prefix like
_rclpy. and same suffix like
.so but a different Python version / architecture) you are using a different Python interpreter than which was used to build the C extension.
Be sure to use the same Python interpreter as the one used to build the binary.
For example, such a mismatch can crop up after an update of the OS. Then, rebuilding the workspace may fix the issue.
Internal compiler error
If you experience an ICE when trying to compile on a memory constrained platform like a Raspberry PI you might want to build single threaded (prefix the build invocation with
Out of memory
ros1_bridge in its current form requires 4Gb of free RAM to compile.
If you don’t have that amount of RAM available it’s suggested to use
COLCON_IGNORE in that folder and skip its compilation.
Multiple host interference
If you’re running multiple instances on the same network you may get interference.
To avoid this you can set the environment variable
ROS_DOMAIN_ID to a different integer, the default is zero.
This will define the DDS domain id for your system.
Note that if you are using the OpenSplice DDS implementation you will also need to update the OpenSplice configuration file accordingly.
The location of the configuration file is referenced in the
OSPL_URI environment variable.
Segmentation fault when using
pyenv seems to default to building Python with
.a files, but that causes issues with
rclpy, so it’s recommended to build Python with Frameworks enabled on macOS when using
Library not loaded; image not found
If you are seeing library loading issues at runtime (either running tests or running nodes), such as the following:
ImportError: dlopen(.../ros2_<distro>/ros2-osx/lib/python3.7/site-packages/rclpy/_rclpy.cpython-37m-darwin.so, 2): Library not loaded: @rpath/librcl_interfaces__rosidl_typesupport_c.dylib Referenced from: .../ros2_<distro>/ros2-osx/lib/python3.7/site-packages/rclpy/_rclpy.cpython-37m-darwin.so Reason: image not found
Then you probably have System Integrity Protection enabled. Follow these instructions to disable System Integrity Protection (SIP).
Qt build error:
unknown type name 'Q_ENUM'
If you see build errors related to Qt, e.g.:
In file included from /usr/local/opt/qt/lib/QtGui.framework/Headers/qguiapplication.h:46: /usr/local/opt/qt/lib/QtGui.framework/Headers/qinputmethod.h:87:5: error: unknown type name 'Q_ENUM' Q_ENUM(Action) ^
you may be using qt4 instead of qt5: see https://github.com/ros2/ros2/issues/441
Missing symbol when opencv (and therefore libjpeg, libtiff, and libpng) are installed with Homebrew
If you have opencv installed you might get this:
dyld: Symbol not found: __cg_jpeg_resync_to_restart Referenced from: /System/Library/Frameworks/ImageIO.framework/Versions/A/ImageIO Expected in: /usr/local/lib/libJPEG.dylib in /System/Library/Frameworks/ImageIO.framework/Versions/A/ImageIO /bin/sh: line 1: 25274 Trace/BPT trap: 5 /usr/local/bin/cmake
If so, to build you’ll have to do this:
$ brew unlink libpng libtiff libjpeg
But this will break opencv, so you’ll also need to update it to continue working:
$ sudo install_name_tool -change /usr/local/lib/libjpeg.8.dylib /usr/local/opt/jpeg/lib/libjpeg.8.dylib /usr/local/lib/libopencv_highgui.2.4.dylib $ sudo install_name_tool -change /usr/local/lib/libpng16.16.dylib /usr/local/opt/libpng/lib/libpng16.16.dylib /usr/local/lib/libopencv_highgui.2.4.dylib $ sudo install_name_tool -change /usr/local/lib/libtiff.5.dylib /usr/local/opt/libtiff/lib/libtiff.5.dylib /usr/local/lib/libopencv_highgui.2.4.dylib $ sudo install_name_tool -change /usr/local/lib/libjpeg.8.dylib /usr/local/opt/jpeg/lib/libjpeg.8.dylib /usr/local/Cellar/libtiff/4.0.4/lib/libtiff.5.dylib
The first command is necessary to avoid things built against the system libjpeg (etc.) from getting the version in /usr/local/lib. The others are updating things built by Homebrew so that they can find the version of libjpeg (etc.) without having them in /usr/local/lib.
rosdep install error
homebrew: Failed to detect successful installation of [qt5]
While following the Creating a workspace tutorial, you might encounter the following error stating that
rosdep failes to install Qt5.
$ rosdep install -i --from-path src --rosdistro dashing -y executing command [brew install qt5] Warning: qt 5.15.0 is already installed and up-to-date To reinstall 5.15.0, run `brew reinstall qt` ERROR: the following rosdeps failed to install homebrew: Failed to detect successful installation of [qt5]
This error seems to stem from a linking issue and can be resolved by running the following command.
$ cd /usr/local/Cellar $ sudo ln -s qt qt5
rosdep command should now execute normally:
$ rosdep install -i --from-path src --rosdistro dashing -y #All required rosdeps installed successfully
Import failing even with library present on the system
rclpy fails to be imported because of some missing DLLs on your system.
If so, make sure to install all the dependencies listed in the “Installing prerequisites” sections of the installation instructions).
If you are installing from binaries, you may need to update your dependencies: they must be the same version as those used to build the binaries.
If you are still having issues, you can use the Dependencies tool to determine which dependencies are missing on your system.
Use the tool to load the corresponding
.pyd file, and it should report unavailable
Be sure that the current workspace is sourced before you execute the tool, otherwise there will be unresolved ROS DLL files.
Use this information to install additional dependencies or adjust your path as necessary.
CMake error setting modification time
If you run into the CMake error
file INSTALL cannot set modification time on ... when installing files it is likely that an anti virus software or Windows Defender are interfering with the build. E.g. for Windows Defender you can list the workspace location to be excluded to prevent it from scanning those files.
260 character path limit
The input line is too long. The syntax of the command is incorrect.
Depending on your directory hierarchy, you may see path length limit errors when building ROS 2 from source or your own libraries.
To allow deeper path lengths:
regedit.exe, navigate to
Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem, and set
LongPathsEnabled to 0x00000001 (1).
Hit the windows key and type
Edit Group Policy.
Navigate to Local Computer Policy > Computer Configuration > Administrative Templates > System > Filesystem.
Enable Win32 long paths, click Edit.
In the dialog, select Enabled and click OK.
Close and open your terminal to reset the environment and try building again.
CMake packages unable to find asio, tinyxml2, tinyxml, eigen, or log4cxx
We’ve seen that sometimes the chocolatey packages for
tinyxml2, etc. do not add important registry entries and CMake will be unable to find them when building ROS 2.
We’ve not yet been able to identify the root cause, but uninstalling the chocolatey packages (with
-n if the uninstall fails the first time), and then reinstalling them will fix the issue.
patch.exe opens a new command window and asks for administrator
This will also cause the build of packages which need to use patch to fail, even you allow it to use administrator rights.
Make sure you’re building in a Visual Studio command prompt which has been run as administrator.
On some machines canceling the prompt without selecting “Yes” will also work.
Binary installation specific
If your example does not start because of missing DLLs, please verify that all libraries from external dependencies such as OpenCV are located inside your
If you forget to call the
local_setup.batfile from your terminal, the demo programs will most likely crash immediately.