Article · Wikipedia archive · Last revised Jul 5, 2026

BareMetal

BareMetal is an exokernel-based single address space operating system (OS) created by Return Infinity.

Last revised
Jul 5, 2026
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≈ 3 min
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BareMetal
DeveloperReturn Infinity
Written inAssembly
Working stateCurrent
Source modelOpen source
Initial release2008 (2008)
Latest release2025.04 / April 30, 2025 (2025-04-30)1
Marketing targetHPCs, HTC, Cloud computing
Available inEnglish
Supported platformsx86-64
Kernel typeExokernel, SASOS
UserlandUnknown
Default
user interface		Command-line
LicenseBSD License2
Official websitewww.returninfinity.com

BareMetal is an exokernel-based single address space operating system (OS) created by Return Infinity.

It is written in assembly to achieve high-performance computing with minimal footprint34 with a "just enough operating system" (JeOS) approach.5 The operating system is primarily targeted towards virtualized environments for cloud computing, or HPCs due to its design as a lightweight kernel (LWK). It could be used as a unikernel.

It was inspired by another OS written in assembly, MikeOS,2 and it is a recent example of an operating system that is not written in C or C++, nor based on Unix-like kernels.6

Overview

Hardware requirements

Source:7

  • AMD/Intel based 64-bit computer
  • Memory: 4 MB (plus 2 MB for every additional core)
  • Hard Disk: 32 MB

Supported devices

Source:8

  • Bus - PCIe, PCI, xHCI
  • Non-volatile storage - NVMe, AHCI (SATA), ATA, Virtio-Blk
  • Ethernet - Intel 8259x 10-gigabit, Intel 8254x/8257x Gigabit, Realtek 816x/811x Gigabit, Virtio-Net

One task per core

Multitasking on BareMetal is unusual for modern operating systems. BareMetal uses an internal work queue that all CPU cores poll. A task added to the work queue will be processed by any available CPU core in the system and will execute until completion, which results in no context switch overhead.9

Programming

API

An API is documented10 but, in line with its philosophy, the OS does not enforce entry points for system calls (e.g.: no call gates or other safety mechanisms).

C

BareMetal OS has a build script to pull the latest code, make the needed changes, and then compile C code using11 the Newlib C standard library.12

C++

A mostly-complete C++11 Standard Library was designed and developed for working in ring 0.13 The main goal of such library is providing, on a library level, an alternative to hardware memory protection used in classical OSes, with help of carefully designed classes.14

K

k for BareMetal:15 a port of k edu from shakti16 by Jack Andrews. At this stage, it is just a proof of concept and doesn't integrate the BareMetal file system.

Rust

A Rust program demonstration was added to the programs in November 2014, demonstrating the ability to write Rust programs for BareMetal OS.17

Networking

TCP/IP stack

A TCP/IP stack was the #1 feature request.18 A port of lwIP written in C was announced in October 2014.19

minIP,20 a minimalist IP stack in ANSI C able to provide enough functionalities to serve a simple static webpage, is being developed as a proof of concept to learn the fundamentals in preparation for an x86-64 assembly re-write planned for the future.

References

References

  1. Seyler, Ian. "Releases · ReturnInfinity/BareMetal". BareMetal OS GitHub repository. Retrieved May 19, 2025.
  2. Voorsanger, Conrad (June 2, 2011). "Interview With Baremetal OS' Ian Seyler". OSNews. Retrieved May 26, 2014.
  3. Adams, David (July 14, 2010). "BareMetal OS". OSNews. Retrieved May 26, 2014.
  4. Benchoff, Brian (May 27, 2011). "64-bit OS written entirely in assembly". Hack A Day. Retrieved May 26, 2014.
  5. Seyler, Ian. "Return Infinity (home page), The BareMetal advantage". Return Infinity. Retrieved February 2, 2015.
  6. Smith, Jesse (July 19, 2010). "DistroWatch Weekly, Issue 363". DistroWatch. Retrieved May 26, 2014.
  7. "BareMetal OS Requirements". Return Infinity (archived copy at Wayback Machine). Archived from the original on September 6, 2014. Retrieved September 6, 2014.
  8. Seyler, Ian. "Supported Hardware". BareMetal OS GitHub repository. Retrieved May 19, 2025.
  9. "BareMetal OS Queue". Retrieved April 28, 2015.
  10. Seyler, Ian. "API documentation". BareMetal OS GitHub repository. Retrieved June 26, 2015.
  11. Seyler, Ian (January 17, 2014). "Newlib build script". BeareMetal OS Google Group. Retrieved February 2, 2015.
  12. Seyler, Ian. "newlib.sh". Build scripts for BareMetal OS and its related utilities, GitHub repository. Retrieved February 2, 2015.
  13. Lodyagin, Sergei (November 17, 2013). "Bare C++ library". BeareMetal OS Google Group. Retrieved February 2, 2015.
  14. Lodyagin, Sergei. "The Bare C++ library". The Bare C++ library GitHub repository. Retrieved February 2, 2015.
  15. Andrews, Jack (December 10, 2024). "ReturnInfinity/kbm: k for BareMetal". BeareMetal OS port of k edu. Retrieved May 19, 2025.
  16. Whitney, Arthur. "shakti". k edu at shakti. Retrieved May 19, 2025.
  17. Seyler, Ian. "Add Rust example". BareMetal OS GitHub repository (legacy version). Retrieved March 18, 2018.
  18. Seyler, Ian (August 22, 2013). "TCP/IP". BeareMetal OS Google Group. Retrieved February 2, 2015.
  19. Seyler, Ian (October 31, 2014). "BareMetal and lwIP". BeareMetal OS Google Group. Retrieved February 2, 2015.
  20. Seyler, Ian. "minIP - A minimalist IP stack written in ANSI C". BareMetal OS GitHub repository. Retrieved May 24, 2017.
External links