Releases and Active Development
  • The current release is 5.1 (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.


March 23, 2021

RTEMS now has a Discord server ( Feel free to drop by and chat.

October 22, 2020

EPICS Community held the EPICS Collaboration Fall Meeting 2020 virtually due to the pandemic. This meeting included presentations from core RTEMS developers.

  • Gedare Bloom presented...
August 25, 2020

The RTEMS Project is proud to announce the availability of the 5.1 release of RTEMS. It is available from which includes formatted...

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...