Releases and Active Development
  • The current release is 5.3 (download here). Note that this release branch was planned to be 4.12 but significant changes warranted bumping the major number (e.g. 4 to 5). The new release numbering scheme is described here.
  • The previous release series was 4.11 and the last release from that branch is 4.11.3 (download here).
  • The next release branch is planned to be 6. For details and status, visit the Release page. This is the git master.
  • Information on older releases is available here.

What is RTEMS?

The Real-Time Executive for Multiprocessor Systems or RTEMS is an open source Real Time Operating System (RTOS) that supports open standard application programming interfaces (API) such as POSIX. It is used in space flight, medical, networking and many more embedded devices. RTEMS currently supports 18 processor architectures and approximately 200 BSPs. These include ARM, PowerPC, Intel, SPARC, RISC-V, MIPS, and more. RTEMS includes multiple file systems, symmetric multiprocessing (SMP), embedded shell, and dynamic loading as well as a high-performance, full-featured IPV4/IPV6 TCP/IP stack from FreeBSD which also provides RTEMS with USB.

Major decisions about RTEMS are made by the core developers in concert with the user community, guided by the Mission Statement. We provide access to our development sources via a Git Repository (see these Instructions for details). We strive to provide regular, high-quality releases, which we want to work well on a wide range of embedded targets using cross development from a variety of hosts including GNU/Linux distributions, MS Windows, BSDs, Solaris, and Mac OS. We encourage everyone to contribute changes and feedback to RTEMS.

Commercial support is available from US and European companies, and free support comes via the active global community.


June 24, 2020

Episode 335: Patching on the Surface of Mars of features Joel Sherrill from the the RTEMS community. The title is a nod to the interesting presentation Patching Flight Software on Mars from the...

May 16, 2020

Joel Sherrill and Gedare Bloom have a paper at the IEEE ISORC 2020 conference which will be presented on 20 May 2020. This paper is titled "Harmonizing ARINC 653 and Realtime POSIX for Conformance to the FACE Technical Standard" and discusses OAR Corporation's effort to paravirtualize...

May 04, 2020

Today is the 25th birthday of the oldest commit in the RTEMS public source code revision...

January 14, 2020

The 2019 edition of the Flight Software Workshop was held in Huntsville Alabama, home of OAR Corporation. This FSW was a huge success with great presentations. The presentations included discussions of many interesting projects using RTEMS. The...

December 14, 2019

Matthias Göbel passed along information about the ESA Brave Days ( password BRAVEDAYS-2019) and the GR740 User Day (...

March 19, 2019

The European Space Agency is sponsoring the pre-qualification of RTEMS for space applications. As part of this effort, embedded brains GmbH has prepared a...

January 04, 2019

OAR is planning to host the RTEMS Training class at the OAR Corporate office in Huntsville, AL, USA.

This training session is open to anyone interested in learning specifically about RTEMS, or about real-time, embedded systems in general. Monday is a Kick Start day for learning about and...

August 07, 2018

The RTEMS Foundation has received a letter from On-Line Applications Corporation (OAR) which grants the RTEMS Community permission to relicense OAR's current and future contributions. The letter is attached as a PDF to ticket 3053 and the text of the...

June 19, 2018

OAR Corporation will hold an Open RTEMS Training Class in Huntsville, Alabama, during the week of October 1-5, 2018.

The RTEMS Kickstart Class will be held on Monday followed by the RTEMS Open Class on Tuesday through Friday. This training is open to all registered persons. For more...

January 25, 2018

In 2018, OAR Corporation will host two RTEMS training sessions in Huntsville, Alabama, USA.

The April class schedule is:

Kick Start - April 23, 2018
For information and registration, see...