NetBSD was originally derived from the 4.3BSD-Reno release of the Berkeley Software Distribution from the Computer Systems Research Group of the University of California, Berkeley, via its Net/2 source code release and the 386BSD project.[5] The NetBSD project began as a result of frustration within the 386BSD developer community with the pace and direction of the operating system's development.[11] The four founders of the NetBSD project, Chris Demetriou, Theo de Raadt, Adam Glass, and Charles Hannum, felt that a more open development model would benefit the project: one centered on portable, clean, correct code. They aimed to produce a unified, multi-platform, production-quality, BSD-based operating system. The name "NetBSD" was chosen based on the importance and growth of networks such as the Internet at that time, and the distributed, collaborative nature of its development.[12]
The NetBSD source code repository was established on 21 March 1993 and the first official release, NetBSD 0.8, was made on 19 April 1993.[13] This was derived from 386BSD 0.1 plus the version 0.2.2 unofficial patchkit, with several programs from the Net/2 release missing from 386BSD re-integrated, and various other improvements.[13][14] The first multi-platform release, NetBSD 1.0, was made in October 1994, and being updated with 4.4BSD-Lite sources, it was free of all legally encumbered 4.3BSD Net/2 code.[15] Also in 1994, for disputed reasons, one of the founders, Theo de Raadt, was removed from the project. He later founded a new project, OpenBSD, from a forked version of NetBSD 1.0 near the end of 1995.[16]
In 1998, NetBSD 1.3 introduced the pkgsrc packages collection.[17]
Until 2004, NetBSD 1.x releases were made at roughly annual intervals, with minor "patch" releases in between. From release 2.0 onwards, NetBSD uses semantic versioning, and each major NetBSD release corresponds to an incremented major version number, i.e. the major releases following 2.0 are 3.0, 4.0 and so on. The previous minor releases are now divided into two categories: x.y "stable" maintenance releases and x.y.z releases containing only security and critical fixes.[18]
NetBSD used to ship with twm as a preconfigured graphical interface (window manager); in 2020 (version 9.1) this was changed to the more modern and versatile CTWM.[19]
Features
NetBSD/amd64 startup in console modeNetBSD/amd64 console login and welcome message
As the project's motto ("Of course it runs NetBSD" ) suggests, NetBSD has been ported to a large number of 32- and 64-bitarchitectures. These range from VAXminicomputers to Pocket PCPDAs. NetBSD has also been ported to several video game consoles such as the Sega Dreamcast[20] and the Nintendo Wii.[21] As of 2019, NetBSD supports 59 hardware platforms (across 16 different instruction sets). The kernel and userland for these platforms are all built from a central unified source-code tree managed by CVS. Currently, unlike other kernels such as μClinux, the NetBSD kernel requires the presence of an MMU in any given target architecture.
NetBSD's portability is aided by the use of hardware abstraction layer interfaces for low-level hardware access such as bus input/output or DMA. Using this portability layer, device drivers can be split into "machine-independent" and "machine-dependent" components. This makes a single driver easily usable on several platforms by hiding hardware access details, and reduces the work to port it to a new system.[22]
This permits a particular device driver for a PCI card to work without modifications, whether it is in a PCI slot on an IA-32, Alpha, PowerPC, SPARC, or other architecture with a PCI bus. Also, a single driver for a specific device can operate via several different buses, like ISA, PCI, or PC Card.
In 2005, as a demonstration of NetBSD's portability and suitability for embedded applications, Technologic Systems, a vendor of embedded systems hardware, designed and demonstrated a NetBSD-powered kitchen toaster.[23]
Commercial ports to embedded platforms were available from and supported by Wasabi Systems, including platforms such as the AMD Geode LX800, FreescalePowerQUICC processors, Marvell Orion, AMCC405 family of PowerPC processors, and the IntelXScale IOP and IXP series.
Portable build framework
The NetBSD cross-compiling framework (also known as "build.sh"[24]) lets a developer build a complete NetBSD system for an architecture from a more powerful system of different architecture (cross-compiling), including on a different operating system (the framework supports most POSIX-compliant systems). Several embedded systems using NetBSD have required no additional software development other than toolchain and target rehost.[25]
NetBSD features pkgsrc (short for "package source"), a framework for building and managing third-party application software packages. The pkgsrc collection consists of more than 20,000 packages as of October 2019[update].[26] Building and installing packages such as Lumina, KDE, GNOME, the Apache HTTP Server or Perl is performed through the use of a system of makefiles. This can automatically fetch the source code, unpack, patch, configure, build and install the package such that it can be removed again later. An alternative to compiling from source is to use a precompiled binary package. In either case, any prerequisites/dependencies will be installed automatically by the package system, without need for manual intervention.
pkgsrc supports not only NetBSD, but also several other BSD variants like FreeBSD and Darwin/macOS, and other Unix-like operating systems such as Linux, Solaris, IRIX, and others, as well as Interix. pkgsrc was previously adopted as the official package management system for DragonFly BSD.[27]
Symmetric multiprocessing
NetBSD has supported SMP since the NetBSD 2.0 release in 2004,[28] which was initially implemented using the giant lock approach. During the development cycle of the NetBSD 5 release, major work was done to improve SMP support; most of the kernel subsystems were modified to use the fine-grained locking approach. New synchronization primitives were implemented and scheduler activations was replaced with a 1:1 threading model in February 2007.[29] A scalable M2 thread scheduler was implemented, though the old 4.4BSD scheduler still remains the default but was modified to scale with SMP. Threaded software interrupts were implemented to improve synchronization. The virtual memory system, memory allocator and trap handling were made MP safe. The file system framework, including the VFS and major file systems were modified to be MP safe. Since April 2008 the only subsystems running with a giant lock are the network protocols and most device drivers.
Security
NetBSD provides various features in the security area.[30] The Kernel Authorization framework[31] (or Kauth) is a subsystem managing all authorization requests inside the kernel, and used as system-wide security policy. It allows external modules to plug-in the authorization process. NetBSD also incorporates exploit mitigation features, ASLR,[32] KASLR, restricted mprotect() and Segvguard from the PaX project, and GCCStack Smashing Protection (SSP, or also known as ProPolice, enabled by default since NetBSD 6.0) compiler extensions. Verified Executables (or Veriexec) is an in-kernel file integrity subsystem in NetBSD. It allows the user to set digital fingerprints (hashes) of files, and take a number of different actions if files do not match their fingerprints. For example, one can allow Perl to run only scripts that match their fingerprints.[33] The cryptographic device driver (CGD) allows using disks or partitions (including CDs and DVDs) for encrypted storage.[34]
Virtualization
The Xenvirtual-machine monitor has been supported in NetBSD since release 3.0. The use of Xen requires a special pre-kernel boot environment that loads a Xen-specialized kernel as the "host OS" (Dom0). Any number of "guest OSes" (DomU) virtualized computers, with or without specific Xen/DomU support, can be run in parallel with the appropriate hardware resources.
The need for a third-party boot manager, such as GRUB, was eliminated with NetBSD 5's Xen-compatible boot manager.[35] NetBSD 6 as a Dom0 has been benchmarked comparably to Linux, with better performance than Linux in some tests.[36]
As of NetBSD 9.0, accelerated virtualization is provided through the native hypervisor NVMM (NetBSD Virtual Machine Monitor).[37]
It provides a virtualization API, libnvmm, that can be leveraged by emulators such as QEMU. A unique property of NVMM is that the kernel never accesses guest VM memory, only creating it.[38]
Intel's Hardware Accelerated Execution Manager (HAXM) provides an alternative solution for acceleration in QEMU for Intel CPUs only, similar to Linux's KVM.[39]
NetBSD 5.0 introduced the rump kernel, an architecture to run drivers in user-space by emulating kernel-space calls. This anykernel architecture allows adding support of NetBSD drivers to other kernel architectures, ranging from exokernels to monolithic kernels.[40]
The bio(4) interface for vendor-agnostic RAID volume management through bioctl has been available in NetBSD since 2007.[41]
The WAPBL journaling filesystem, an extension of the BSD FFS filesystem, was contributed by Wasabi Systems in 2008.[42]
The NetBSD Logical Volume Manager is based on a BSD reimplementation of a device-mapper driver and a port of the Linux Logical Volume Manager tools. It was mostly written during the Google Summer of Code 2008.[43]
The ZFS filesystem developed by Sun Microsystems was imported into the NetBSD base system in 2009.
The CHFSFlash memory filesystem was imported into NetBSD in November 2011. CHFS is a file system developed at the Department of Software Engineering, University of Szeged, Hungary, and is the first open source Flash-specific file system written for NetBSD.
Compatibility with other operating systems
At the source code level, NetBSD is very nearly entirely compliant with POSIX.1 (IEEE 1003.1-1990) standard and mostly compliant with POSIX.2 (IEEE 1003.2-1992).
NetBSD provides system call-level binary compatibility on the appropriate processor architectures with its previous releases, but also with several other UNIX-derived and UNIX-like operating systems, including Linux, and other 4.3BSD derivatives like SunOS 4. This allows NetBSD users to run many applications that are only distributed in binary form for other operating systems, usually with no significant loss of performance.[44]
Kernel-space scripting with the Lua programming language was added in NetBSD 7.0.[45] The Lua language (i.e., its interpreter and standard libraries) was initially ported to the NetBSD kernel during Google Summer of Code 2010 and has undergone several improvements since then. There are two main differences between user and kernel space Lua: kernel Lua does not support floating-point numbers; as such, only Lua integers are available. It also does not have full support to user space libraries that rely on the operating system (e.g., io and os).
NetBSD has featured a native hardware monitoring framework since 1999/2000. In 2003, it served as the inspiration behind the OpenBSD's sysctl hw.sensors framework when some NetBSD drivers were being ported to OpenBSD.[46]
As of March 2019[update], NetBSD had close to 85 device drivers exporting data through the API of the envsys framework. Since the 2007 revision, serialisation of data between the kernel and userland is done through XML property lists with the help of NetBSD's proplib(3).
NetBSD's clean design, high performance, scalability, and support for many architectures has led to its use in embedded devices and servers, especially in networking applications.[48]
Dell Force10 uses NetBSD as the underlying operating system that powers FTOS (the Force10 Operating System), which is used in high scalability switch/routers.[51] Force10 also made a donation to the NetBSD Foundation in 2007 to help further research and the open development community.[52]
Wasabi Systems provides a commercial Wasabi Certified BSD product based on NetBSD with proprietary enterprise features and extensions, which are focused on embedded, server and storage applications.[53]
In 2004, SUNET used NetBSD to set the Internet2 Land Speed Record. NetBSD was chosen "due to the scalability of the TCP code".[58]
NetBSD is also used in Apple'sAirPort Extreme and Time Capsule products,[59][60] instead of Apple's own OS X (of which most Unix-level userland code is derived from FreeBSD code but some is derived from NetBSD code[61][62]).
The Minix operating system uses a mostly NetBSD userland as well as its pkgsrc packages infrastructure since version 3.2.[64]
Parts of macOS were originally taken from NetBSD, such as some userspace command line tools.[65][66][67]
Licensing
All of the NetBSD kernel and most of the core userland source code is released under the terms of the BSD License (two, three, and four-clause variants). This essentially allows everyone to use, modify, redistribute or sell it as they wish, as long as they do not remove the copyright notice and license text (the four-clause variants also include terms relating to publicity material). Thus, the development of products based on NetBSD is possible without having to make modifications to the source code public. In contrast, the GPL, which does not apply to NetBSD, stipulates that changes to source code of a product must be released to the product recipient when products derived from those changes are released.
On 20 June 2008, the NetBSD Foundation announced a transition to the two clause BSD license, citing concerns with UCB support of clause 3 and industry applicability of clause 4.[68]
NetBSD also includes the GNU development tools and other packages, which are covered by the GPL and other open source licenses. As with other BSD projects, NetBSD separates those in its base source tree to make it easier to remove code that is under more restrictive licenses.[69] As for packages, the installed software licenses may be controlled by modifying the list of allowed licenses in the pkgsrc configuration file (mk.conf).
Releases
The following table lists major NetBSD releases and their notable features in reverse chronological order. Minor and patch releases are not included.
Support for new AArch64 security features: Privileged Access Never, Pointer Authentication, Branch Target Identification. Support for Linux binary compatibility on AArch64.
Support for PVH Xen virtualization, paravirtualization and multiprocessor Dom0 support in Xen
SMP support for Xen domU kernels, initial suspend/resume support for Xen domU, PCI pass-through support for Xen3, and addition of the balloon driver
Major rework of MIPS port adding support for Symmetric multiprocessing and 64-bit (O32, N32, N64 ABIs are supported) processors, DSP v2 ASE extension, various NetLogic/RMI processor models, Loongson family processors, and new SoC boards
Improved SMP on PowerPC port and added support for Book E Freescale MPC85xx (e500 core) processors
Rewritten Loadable kernel module framework, which will replace old LKMs. Use of X.Org rather than XFree86 by default for i386 and amd64 ports, and introduction of drm(4)/DRI for 3D hardware acceleration. Preliminary support for using Clang instead of GCC as the system compiler.[82]
Added support for ASLR in the kernel and dynamic linker.
Rewritten envsys framework (envsys2); addition of 8 new Hardware Monitoring sensor drivers; new I2C attachment of the lm(4) driver; additional hardware support in several sensor drivers[79]
The legally encumbered Net/2-derived source code was replaced with equivalent code from 4.4BSD-lite, in accordance with the USL v BSDi lawsuit settlement.
The first official release, derived from 386BSD 0.1 plus the version 0.2.2 unofficial patchkit, with several programs from the Net/2 release missing from 386BSD re-integrated, and various other improvements.[95]
Logo
The NetBSD "flag" logo, designed by Grant Bissett, was introduced in 2004 and is an abstraction of the older logo,[96] which was designed by Shawn Mueller in 1994. Mueller's version was based on the famous World War II photograph Raising the Flag on Iwo Jima.[97]
The NetBSD Foundation
The NetBSD Foundation is the legal entity that owns the intellectual property and trademarks associated with NetBSD,[98] and on 22 January 2004, became a 501(c)3 tax-exempt non-profit organization. The members of the foundation are developers who have CVS commit access.[99] The NetBSD Foundation has a Board of Directors, elected by the voting of members for two years.[100]
Hosting
Hosting for the project is provided primarily by Columbia University, and Western Washington University, fronted by a CDN provided by Fastly. Mirrors for the project are spread around the world and provided by volunteers and supporters of the project.
Commit guidelines
The project defines guidelines to make commits to its CVS source tree. On April 4, 2004, its first version, 1.1, was published. [101] The 10 guidelines of this version can be summarized as:[102][103]
Commit only familiar code you are familiar with;
Do not commit tainted code to the repository, i.e., if the code is not yours, check its license;
The more intrusive your changes are the higher is the level of required prior approval;
Commit only code that you have tested;
Group commits together that are part of the same fix;
Each commit should be a separate patch/fix/addition/etc.;
Do not mix functionality or bug-fix patches with whitespace/layout updates;
Clearly document your changes in the commit log;
Give proper credit if your commit contains code;
Do not revert other developer's commits, try to reach an agreement.
In May 2024, the second guideline was extended to state that code generated by "large language model or similar technology" must not be committed without prior written approval by core. [104][105]
^Ganssle, Jack G; Noergaard, Tammy; Eady, Fred; Edwards, Lewin; Katz, David J (14 September 2007). Embedded Hardware. Newnes. ISBN978-0-7506-8584-9. pp. 291–292.
^"About NetBSD". The NetBSD Foundation, Inc. The NetBSD Project's goals. Retrieved 26 September 2023.
^"NetBSD features list". The NetBSD Foundation, Inc. Archived from the original on 6 August 2011. Retrieved 7 June 2014. NetBSD focuses on clean design and well architected solutions.
^Love, Robert (2005). "Chapter 19". Linux Kernel development (2. ed.). Sams Publishing. ISBN0-672-32720-1. Retrieved 7 June 2014. Some examples of highly portable operating systems are Minix, NetBSD, and many research systems.
^"Myths about FreeBSD". Retrieved 7 June 2014. The two operating systems do share a lot of code, for example most userland utilities and the C library on OS X are derived from FreeBSD versions.
^"Distro description". Licensing Section: Free Penguin. Retrieved 7 June 2014. NetBSD separates those in its base source tree, in order to make removal of code under more restrictive licenses easier.
