as pointed out by Philippe, each of us proposed a different alternative to the use of the RTAI VxWorks skin in kernel mode. These two alternatives might lead to confusion. So, let us state it clearly. There are three ways to use the RTAI VxWorks skin. First way: User-space VM. If you want the comfort of user space realtime and are willing to accept the tradeoffs it implies, you can use the so called VxWorks virtual machine. In the configuration menu (make config, menuconfig or xconfig) activate the options: Core system / Xenomai sub-system / User-space VM support Add-ons / Xenomai skins / VxWorks emulator After installation, you will find a few libraries in the directory rtai-config --libdir`. In order to run your VxWorks code in userspace realtime, you will have to link it (please Philippe correct me if I am wrong) with: libvxworks.a libxenomai.a libfusion.a Second way: Kernel space. If you can not afford the comfort of user space, you have to compile and use the VxWorks skin as a kernel module (but have a look at the third way, it might help you). In the configuration menu, activate the option: Add-ons / Xenomai skins / VxWorks emulator Repeating what Philippe wrote, you then have to compile your program as a kernel module, using rtai-config --module-cflags, and insmod the following modules: adeos.o (unless statically bound to the kernel) rtai_hal.o rtai_xeno.o rtai_vxworks.o your_app_module.o Third way: The RTAI simulator. If you plan to use kernel space, but would like to run your code in a simulator before you give it a chance to cause kernel oopses, you should definitely try this third way. In the configuration menu, activate the options: Add-ons / Xenomai skins / VxWorks emulator RTAI Simulator / Minute Virtual Machine RTAI Simulator / GCC tarball (give a path) You have to download a gcc (version 2.95.3) tarball from your nearest GNU ftp mirror and provide the path to RTAI Simulator configuration system. As part of the compilation process, gcc sources will be patched, compiled and an instrumented compiler, gcic, will be installed. In order to compile your code for the RTAI simulator, you need to compile it with gcic and link it with the following libraries: libvxworks_s.a libxenomai_s.a libmvm.so or libmvm.a (or libmvm.la if you use libtool) libmvmutils.so, libmvmutils.a or libmvmutils.la libxenosa.a You will then be able to run your code into the xenoscope, a graphical, real-time OS aware debugger. For the moment, there is no support for this into rtai-config, but you may give a look at the "satch" example (it uses the psos skin, but this does not make a great difference). You will find it in the directory rtai-sim/examples/psos+/satch. The same goes for the other skins, namely psos+, vrtx and uitron. pse51 is a little bit different, it has no user-space VM support.