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78-413: An ESP contains the boot loaders , boot managers , or kernel images of installed operating systems (which are typically contained in other partitions), device driver files for hardware devices present in a computer and used by the firmware at boot time, system utility programs that are intended to be run before an operating system is booted, and data files such as error logs. The EFI system partition

156-524: A task switcher in Intel 80386 assembly language and a terminal driver . On 25 August 1991, Torvalds posted the following to comp.os.minix , a newsgroup on Usenet : I'm doing a (free) operating system (just a hobby, won't be big and professional like gnu) for 386(486) AT clones. This has been brewing since April, and is starting to get ready. I'd like any feedback on things people like/dislike in minix, as my OS resembles it somewhat (same physical layout of

234-451: A version control system thus far, in 2002, Linux developers adopted BitKeeper , which was made freely available to them even though it was not free software . In 2005, because of efforts to reverse-engineer it, the company which owned the software revoked its support of the Linux community. In response, Torvalds and others wrote Git . The new system was written within weeks, and in two months

312-568: A Linux Kernel Code of Conflict was introduced on 8 March 2015. It was replaced on 16 September 2018 by a new Code of Conduct based on the Contributor Covenant . This coincided with a public apology by Torvalds and a brief break from kernel development. On 30 November 2018, complying with the Code of Conduct , Jarkko Sakkinen of Intel sent out patches replacing instances of "fuck" appearing in source code comments with suitable versions focused on

390-538: A basic execution environment , and locates the second-stage bootloader. Its primary challenge lies in accomplishing these tasks within strict size constraints while handling potential hardware failures. The bootloader must navigate disk structures, often implementing FAT file system support, and manage the delicate transition from the BIOS startup state to a stable environment for the next boot stage. Boot loaders may face peculiar constraints, especially in size; for instance, on

468-626: A basic shell (as in GNU GRUB), or even games (see List of PC booter games ). Some boot loaders can also load other boot loaders; for example, GRUB loads BOOTMGR instead of loading Windows directly. Usually, a default choice is preselected with a time delay during which a user can press a key to change the choice; after this delay, the default choice is automatically run so normal booting can occur without interaction. They may also handle compression, cryptographic verification, and chain-loading of other bootloaders. The boot process can be considered complete when

546-441: A bit in that more features were made available throughout the series, including support for Bluetooth , Logical Volume Manager (LVM) version 1, RAID support, InterMezzo and ext3 file systems. Version 2.6.0 was released on 17 December 2003. The development for 2.6. x changed further towards including new features throughout the series. Among the changes that have been made in the 2.6 series are: integration of μClinux into

624-523: A boot loader needs to be stored according to the standard ESP file hierarchy, or by providing a complete path of a boot loader to the system's boot manager. On the other hand, FAT32 is always expected on fixed drives. GRUB 2 , elilo and systemd-boot serve as conventional, full-fledged standalone UEFI boot managers (a.k.a. bootloader managers) for Linux. Once loaded by a UEFI firmware, they can access and boot kernel images from all devices, partitions and file systems they support, without being limited to

702-503: A boot loader reaching over two physical sectors, using 386 instructions for size reasons. At the same time, other vendors managed to squeeze much more functionality into a single boot sector without relaxing the original constraints on only minimal available memory (32 KiB) and processor support (8088/8086). For example, DR-DOS boot sectors are able to locate the boot file in the FAT12, FAT16 and FAT32 file systems, and load it into memory as

780-400: A mere process within that system, and then irrevocably transfer control to the operating system. The boot loader then terminates normally as any other process would. Most computers are also capable of booting over a computer network . In this scenario, the operating system is stored on the disk of a server , and certain parts of it are transferred to the client using a simple protocol such as

858-552: A peripheral device, may load a very small number of fixed instructions into memory at a specific location, initialize at least one CPU, and then point the CPU to the instructions and start their execution. These instructions typically start an input operation from some peripheral device (which may be switch-selectable by the operator). Other systems may send hardware commands directly to peripheral devices or I/O controllers that cause an extremely simple input operation (such as "read sector zero of

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936-418: A relatively small program stored in read-only memory (ROM, and later EEPROM , NOR flash ) along with some needed data, to initialize RAM (especially on x86 systems), to access the nonvolatile device (usually block device , e.g., NAND flash) or devices from which the operating system programs and data can be loaded into RAM. Some earlier computer systems, upon receiving a boot signal from a human operator or

1014-483: A roadmap, there are technical guidelines. Instead of a central resource allocation, there are persons and companies who all have a stake in the further development of the Linux kernel, quite independently from one another: People like Linus Torvalds and I don’t plan the kernel evolution. We don’t sit there and think up the roadmap for the next two years, then assign resources to the various new features. That's because we don’t have any resources. The resources are all owned by

1092-505: A single kernel image to work in any boot environment. Linux kernel's support for the EFI Boot Stub is enabled by turning on option CONFIG_EFI_STUB (EFI stub support) during the kernel configuration. It was merged into version 3.3 of the Linux kernel mainline , released on March 18, 2012. Systemd-boot is a simple UEFI boot manager that loads and runs configured EFI images, accessing only

1170-422: A small program from a special section (most commonly the boot sector ) of the most promising device, typically starting at a fixed entry point such as the start of the sector. A first-stage bootloader is a compact 512-byte program that resides in the master boot record (MBR) and executes when a computer starts. Running in 16-bit real mode at address 0x7C00, it performs minimal hardware initialization , sets up

1248-506: A study issued by the Linux Foundation, covering the commits for the releases 4.8 to 4.13, about 1500 developers were contributing from about 200–250 companies on average. The top 30 developers contributed a little more than 16% of the code. For companies, the top contributors are Intel (13.1%) and Red Hat (7.2%), Linaro (5.6%), IBM (4.1%), the second and fifth places are held by the 'none' (8.2%) and 'unknown' (4.1%) categories. Instead of

1326-430: A whole via CHS or LBA, even if the file is not stored in a fixed location and in consecutive sectors. BIOS and UEFI can not only load multiple operating systems from a non-volatile device, they can also initialize system hardware for the loaded operating systems. Examples of first-stage bootloaders include BIOS , UEFI , coreboot , Libreboot , and Das U-Boot . Second-stage bootloaders operate without

1404-544: Is monolithic in an architectural sense since the entire OS runs in kernel space . Linux is provided under the GNU General Public License version 2 , although it contains files under other compatible licenses . In April 1991, Linus Torvalds, a 21-year-old computer science student at the University of Helsinki started working on an operating system, inspired by UNIX, for a personal computer. He started with

1482-492: Is a computer program that is responsible for booting a computer. If it also provides an interactive menu with multiple boot choices then it's often called a boot manager . When a computer is turned off, its software‍—‌including operating systems, application code, and data‍—‌remains stored on non-volatile memory . When the computer is powered on, it typically does not have an operating system or its loader in random-access memory (RAM). The computer first executes

1560-491: Is a monolithic kernel rather than a microkernel was the topic of a debate between Andrew S. Tanenbaum , the creator of MINIX, and Torvalds. The Tanenbaum–Torvalds debate started in 1992 on the Usenet group comp.os.minix as a general discussion about kernel architectures. Version 0.95 was the first capable of running the X Window System . In March 1994, Linux 1.0.0 was released with 176,250 lines of code. As indicated by

1638-438: Is booted. EFI Boot Stub makes it possible to boot a Linux kernel image without the use of a conventional UEFI boot loader. By masquerading as a PE / COFF executable image and appearing to the firmware as a UEFI application, a Linux kernel image with EFI Boot Stub enabled can be directly loaded and executed by a UEFI firmware. Such kernel images can still be loaded and run by BIOS-based boot loaders; thus, EFI Boot Stub allows

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1716-533: Is formatted with a file system whose specification is based on the FAT file system and maintained as part of the UEFI specification; therefore, the file system specification is independent from the original FAT specification. The actual extent of divergence is unknown: Apple maintains a separate tool that should be used on Intel/x86-64 Macs, while other systems use FAT utilities just fine. The globally unique identifier (GUID) for

1794-456: Is located at the \EFI\Microsoft\Boot\ subfolder of the EFI system partition. On Windows XP 64-Bit Edition and later, access to the EFI system partition is obtained by running the mountvol command. Mounts the EFI system partition on the specified drive. Available on Itanium-based computers only. Boot loader A bootloader , also spelled as boot loader or called bootstrap loader ,

1872-455: Is necessary, because the loading can be precomputed and stored on the ROM when the device is made. Large and complex systems may have boot procedures that proceed in multiple phases until finally the operating system and other programs are loaded and ready to execute. Because operating systems are designed as if they never start or stop, a boot loader might load the operating system, configure itself as

1950-541: Is significantly responsible for rising use of Linux overall. The cost to redevelop version 2.6.0 of the Linux kernel in a traditional proprietary development setting has been estimated to be US$ 612 million (€467M, £394M) in 2004 prices using the COCOMO person-month estimation model. In 2006, a study funded by the European Union put the redevelopment cost of kernel version 2.6.8 higher, at €882M ($ 1.14bn, £744M). This topic

2028-448: Is used in many computer systems worldwide. The kernel was created by Linus Torvalds in 1991 and was soon adopted as the kernel for the GNU operating system (OS) which was created to be a free replacement for Unix . Since the late 1990s, it has been included in many operating system distributions , many of which are called Linux . One such Linux kernel operating system is Android which

2106-444: Is used in many mobile and embedded devices. Most of the kernel code is written in C as supported by the GNU compiler collection (GCC) which has extensions beyond standard C. The code also contains assembly code for architecture-specific logic such as optimizing memory use and task execution. The kernel has a modular design such that modules can be integrated as software components – including dynamically loaded. The kernel

2184-594: The Native POSIX Thread Library (NPTL), User-mode Linux integration into the mainline kernel sources, SELinux integration into the mainline kernel sources, InfiniBand support, and considerably more. Starting with 2.6.x releases, the kernel supported a large number of file systems; some designed for Linux, like ext3 , ext4 , FUSE , Btrfs , and others native to other operating systems like JFS , XFS , Minix, Xenix , Irix , Solaris , System V , Windows and MS-DOS . Though development had not used

2262-475: The Trivial File Transfer Protocol (TFTP). After these parts have been transferred, the operating system takes over the control of the booting process. As with the second-stage boot loader, network booting begins by using generic network access methods provided by the network interface's boot ROM, which typically contains a Preboot Execution Environment (PXE) image. No drivers are required, but

2340-1058: The atomic CMPXCHG instruction introduced with the i486 to allow reliable mutexes —making the 3.7 kernel series the last one still supporting the original processor. The same series unified support for the ARM processor. The numbering change from 2.6.39 to 3.0, and from 3.19 to 4.0, involved no meaningful technical differentiation; the major version number was increased simply to avoid large minor numbers. Stable 3.x.y kernels were released until 3.19 in February 2015. Version 3.11, released on 2 September 2013, added many new features such as new O_TMPFILE flag for open(2) to reduce temporary file vulnerabilities, experimental AMD Radeon dynamic power management, low-latency network polling, and zswap (compressed swap cache). In April 2015, Torvalds released kernel version 4.0. By February 2015, Linux had received contributions from nearly 12,000 programmers from more than 1,200 companies, including some of

2418-458: The extended BIOS parameter block on FAT12 and FAT16 volumes since DOS 4.0, whereas the FAT32 EBPB introduced with DOS 7.1 requires even 87 bytes, leaving only 423 bytes for the boot loader when assuming a sector size of 512 bytes. Microsoft boot sectors, therefore, traditionally imposed certain restrictions on the boot process. For example, the boot file had to be located at a fixed position in

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2496-530: The kernel . Many implement modular designs supporting loadable modules for additional functionality. These choices can include different operating systems (for dual or multi-booting from different partitions or drives), different versions of the same operating system (in case a new version has unexpected problems), different operating system loading options (e.g., booting into a rescue or safe mode ), and some standalone programs that can function without an operating system, such as memory testers (e.g., memtest86+ ),

2574-589: The master boot record in order to leave room for the default 64-byte partition table with four partition entries and the two-byte boot signature , which the BIOS requires for a proper boot loader — or even less, when additional features like more than four partition entries (up to 16 with 16 bytes each), a disk signature (6 bytes), a disk timestamp (6 bytes), an Advanced Active Partition (18 bytes) or special multi-boot loaders have to be supported as well in some environments. In floppy and superfloppy volume boot records , up to 59 bytes are occupied for

2652-464: The "core," including architecture-specific code, kernel code, and mm code, while 60% is drivers. Contributions are submitted as patches, in the form of text messages on the Linux kernel mailing list (LKML) (and often also on other mailing lists dedicated to particular subsystems). The patches must conform to a set of rules and to a formal language that, among other things, describes which lines of code are to be deleted and what others are to be added to

2730-568: The "ftp.funet.fi" – FTP server of the Finnish University and Research Network ( FUNET ). It was not even executable since its code still needed Minix to compile and test it. On 5 October 1991, Torvalds announced the first "official" version of Linux, version 0.02. [As] I mentioned a month ago, I'm working on a free version of a Minix-lookalike for AT-386 computers. It has finally reached the stage where it's even usable (though may not be depending on what you want), and I am willing to put out

2808-737: The AMD Radeon FreeSync and NVIDIA Xavier display, fixes for F2FS , EXT4 and XFS , restored support for swap files on the Btrfs file system and continued work on the Intel Icelake Gen11 graphics and on the NXP i.MX8 SoCs. This release was noticeably larger than the rest, Torvalds mentioning that "The overall changes for all of the 5.0 release are much bigger." A total of 1,991 developers, of whom 334 were first-time collaborators, added more than 553,000 lines of code to version 5.8, breaking

2886-465: The BIOS-based CSM booting upon detecting certain types of partition table on the boot disk, effectively preventing UEFI booting from being performed from EFI system partitions contained on MBR-partitioned disks. UEFI firmware supports booting from removable storage devices such as USB flash drives . For that purpose, a removable device is formatted with a FAT12 , FAT16 or FAT32 file system, while

2964-545: The EFI system partition in the GUID Partition Table (GPT) scheme is C12A7328-F81F-11D2-BA4B-00A0C93EC93B , while its ID in the master boot record (MBR) partition-table scheme is 0xEF . Both GPT- and MBR-partitioned disks can contain an EFI system partition, as UEFI firmware is required to support both partitioning schemes. Also, El Torito bootable format for CD-ROMs and DVDs is supported. UEFI provides backward compatibility with legacy systems by reserving

3042-470: The EFI system partition is initially left blank and unused for booting into macOS . However, the EFI system partition is used as a staging area for firmware updates and for the Microsoft Windows bootloader for Mac computers configured to boot into a Windows partition using Boot Camp . Custom Apple UEFI firmware named iBoot controls the logic for finding and loading bootloaders. iBoot will select

3120-417: The EFI system partition. The mount point for the EFI system partition varies depending on the bootloader used. Older bootloaders such as GRUB 2 and lilo/elilo default to /boot/efi . Alternatively, systemd-boot prefers either /efi or /boot over /boot/efi due to potential complications with nested autofs mounts. Regardless of the mount point path, its contents are accessible after Linux

3198-418: The EFI system partition. Configuration file fragments, kernel images and initrd images are required to reside on the EFI system partition, as systemd-boot does not provide support for accessing files on other partitions or file systems. Linux kernels need to be built with CONFIG_EFI_STUB=y so they can be directly executed as UEFI images. On Apple Mac computers using Intel x86-64 processor architecture,

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3276-420: The European Union. As of 7 March 2011 , using then-current LOC (lines of code) of a 2.6.x Linux kernel and wage numbers with David A. Wheeler's calculations it would cost approximately $ 3bn (about €2.2bn) to redevelop the Linux kernel as it keeps getting bigger. An updated calculation as of 26 September 2018 , using then-current 20,088,609 LOC (lines of code) for the 4.14.14 Linux kernel and

3354-540: The Linux 2.2.13 code for the support of the S/390 architecture. Version 2.4.0, released on 4 January 2001, contained support for ISA Plug and Play , USB , and PC Cards . Linux 2.4 added support for the Pentium 4 and Itanium (the latter introduced the ia64 ISA that was jointly developed by Intel and Hewlett-Packard to supersede the older PA-RISC ), and for the newer 64-bit MIPS processor. Development for 2.4. x changed

3432-668: The Linux kernel for its OS. Torvalds labeled the kernel with major version 0 to indicate that it was not yet intended for general use. Version 0.11, released in December 1991, was the first version to be self-hosted ; compiled on a computer running the Linux kernel. When Torvalds released version 0.12 in February 1992, he adopted the GNU General Public License version 2 (GPLv2) over his previous self-drafted license, which had not permitted commercial redistribution. In contrast to Unix , all source files of Linux are freely available, including device drivers . The initial success of Linux

3510-501: The bootstrapping process begins with the CPU executing software contained in ROM (for example, the BIOS of an IBM PC or an IBM PC compatible ) at a predefined address (some CPUs, including the Intel x86 series , are designed to execute this software after reset without outside help). This software contains rudimentary functionality to search for devices eligible to participate in booting, and load

3588-456: The change will either be submitted as a single patch or in multiple patches of source code . In case of a single subsystem that is maintained by a single maintainer, these patches are sent as e-mails to the maintainer of the subsystem with the appropriate mailing list in Cc. The maintainer and the readers of the mailing list will review the patches and provide feedback. Once the review process has finished

3666-450: The computer is ready to interact with the user, or the operating system is capable of running system programs or application programs. Many embedded systems must boot immediately. For example, waiting a minute for a digital television or a GPS navigation device to start is generally unacceptable. Therefore, such devices have software systems in ROM or flash memory so the device can begin functioning immediately; little or no loading

3744-413: The current US national average programmer salary of $ 75,506 show that it would cost approximately $ 14,725,449,000 (£11,191,341,000) to rewrite the existing code. Most who use Linux do so via a Linux distribution . Some distributions ship the vanilla or stable kernel. However, several vendors (such as Red Hat and Debian ) maintain a customized source tree. These are usually updated at a slower pace than

3822-467: The desired bootloader (potentially configured via Startup Keyboard Combinations or NVRAM ), optionally falling back to either the internal macOS Installation, or a recovery system called recoveryOS . Older pre-UEFI Apple–Intel architecture machines required the EFI system partition to be formatted in HFS+ . Third-party bootloaders needed to be "blessed" by a special ioctl command before becoming bootable by

3900-406: The earlier IBM PC and compatibles, a boot sector should typically work with 510 bytes of code (or less) and in only 32 KiB (later relaxed to 64 KiB ) of system memory and only use instructions supported by the original 8088 / 8086 processors. The first stage of PC boot loaders (FSBL, first-stage boot loader) located on fixed disks and removable drives must fit into the first 446 bytes of

3978-530: The file-system (due to practical reasons) among other things). I've currently ported bash (1.08) and gcc (1.40), and things seem to work. This implies that I'll get something practical within a few months [...] Yes - it's free of any minix code, and it has a multi-threaded fs. It is NOT protable [ sic ] (uses 386 task switching etc), and it probably never will support anything other than AT-harddisks, as that's all I have :-(. On 17 September 1991, Torvalds prepared version 0.01 of Linux and put on

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4056-646: The firmware, a relic of the System Folder blessing from Classic Mac OS . There are otherwise no limitations to what kinds of EFI operating system or bootloader an Intel-based Apple computer can run. Devices using Apple silicon ( AArch64 ) such as iPhones, iPads and all Mac computers from 2023 onward do not contain EFI/UEFI functionality and subsequently do not use EFI system partitions. UEFI support in Windows began in 2008 with Windows Vista SP1. The Windows boot manager

4134-633: The first block (sector) of the partition for compatibility code, effectively creating a legacy boot sector . On legacy BIOS -based systems, the first sector of a partition is loaded into memory, and execution is transferred to this code. UEFI firmware does not execute the code in the MBR, except when booting in legacy BIOS mode through the Compatibility Support Module (CSM). The UEFI specification requires MBR partition tables to be fully supported. However, some UEFI implementations immediately switch to

4212-416: The first official kernel made using it was released. In 2005 the stable team was formed as a response to the lack of a kernel tree where people could work on bug fixes , and it would keep updating stable versions. In February 2008 the linux-next tree was created to serve as a place where patches aimed to be merged during the next development cycle gathered. Several subsystem maintainers also adopted

4290-581: The kernel community at the 2017 Embedded Linux Conference Europe. The issues brought up were discussed a few days later at the Maintainers Summit. Concerns over the lack of consistency in how maintainers responded to patches submitted by developers were echoed by Shuah Khan , the maintainer of the kernel self-test framework. Torvalds contended that there would never be consistency in the handling of patches because different kernel subsystems have, over time, adopted different development processes. Therefore, it

4368-570: The kernel so that old programs would work. Version 3.0 was released on 22 July 2011. On 30 May 2011, Torvalds announced that the big change was "NOTHING. Absolutely nothing." and asked, "...let's make sure we really make the next release not just an all new shiny number, but a good kernel too." After the expected 6–7 weeks of the development process, it would be released near the 20th anniversary of Linux. On 11 December 2012, Torvalds decided to reduce kernel complexity by removing support for i386 processors—specifically by not having to emulate

4446-406: The kernel with system software (e.g., the GNU C Library , systemd , and other Unix utilities and daemons ) and a wide selection of application software , but their usage share in desktops is low in comparison to other operating systems. Since Android , which is Linux, accounts for the majority of mobile device operating systems, and due to its rising use in embedded devices , Android

4524-419: The linux.conf.au (LCA) conference in 2018, developers expressed the view that the culture of the community has gotten much better in the past few years. Daniel Vetter, the maintainer of the Intel drm/i915 graphics kernel driver, commented that the "rather violent language and discussion" in the kernel community has decreased or disappeared. Laurent Pinchart asked developers for feedback on their experiences with

4602-537: The mainline kernel sources, PAE support, support for several new lines of CPUs , integration of Advanced Linux Sound Architecture (ALSA) into the mainline kernel sources, support for up to 2 users (up from 2 ), support for up to 2 process IDs (64-bit only, 32-bit architectures still limited to 2 ), substantially increased the number of device types and the number of devices of each type, improved 64-bit support, support for file systems which support file sizes of up to 16 terabytes , in-kernel preemption , support for

4680-601: The operating system subsequently initializes itself and may load extra device drivers . The second-stage boot loader does not need drivers for its own operation, but may instead use generic storage access methods provided by system firmware such as the BIOS or Open Firmware , though typically with restricted hardware functionality and lower performance. Second-stage implementations can include interactive user interfaces, allowing boot option selection and parameter modification. They handle kernel loading, including processing of initrd/initramfs images, and can pass boot parameters to

4758-536: The previous kernel version. The Git kernel source tree names all developers who have contributed to the Linux kernel in the Credits directory and all subsystem maintainers are listed in Maintainers . As with many large open-source software projects, developers are required to adhere to the Contributor Covenant , a code of conduct intended to address harassment of minority contributors. Additionally, to prevent offense

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4836-525: The record previously held by version 4.9. According to the Stack Overflow's annual Developer Survey of 2019, more than the 53% of all respondents have developed software for Linux and about 27% for Android , although only about 25% develop with Linux-based operating systems. Most websites run on Linux-based operating systems , and all of the world's 500 most powerful supercomputers use some form of OS based on Linux. Linux distributions bundle

4914-477: The root directory of the file system and stored within consecutive sectors, conditions taken care of by the SYS command and slightly relaxed in later versions of DOS. The boot loader was then able to load the first three sectors of the file into memory, which happened to contain another embedded boot loader able to load the remainder of the file into memory. When Microsoft added LBA and FAT32 support, they switched to

4992-562: The sources for wider distribution. It is just version 0.02...but I've successfully run bash, gcc, gnu-make, gnu-sed, compress, etc. under it. Linux grew rapidly as many developers, including the MINIX community, contributed to the project. At the time, the GNU Project had completed many components for its free UNIX replacement, the GNU OS , but its kernel, GNU Hurd , was incomplete. The project adopted

5070-437: The specified files. These patches can be automatically processed so that system administrators can apply them in order to make just some changes to the code or to incrementally upgrade to the next version. Linux is distributed also in GNU zip (gzip) and bzip2 formats. A developer who wants to change the Linux kernel writes and tests a code change. Depending on how significant the change is and how many subsystems it modifies,

5148-867: The strict 512-byte limitation of their first-stage counterparts. They execute in a more sophisticated environment, typically ranging from 8KB to several megabytes in size. This expanded space allows implementation of complex features including multiple filesystem support, runtime configuration, and bootloader menu interfaces. Second-stage bootloaders perform comprehensive hardware initialization. They query and configure various system components including memory controllers , interrupt controllers , and essential peripherals. Modern implementations often handle ACPI tables, USB controller initialization, and preliminary graphics setup. Second-stage boot loaders, such as GNU GRUB , rEFInd , BOOTMGR , Syslinux , NTLDR or iBoot , are not themselves operating systems, but are able to load an operating system properly and transfer execution to it;

5226-407: The subsystem maintainer accepts the patches in the relevant Git kernel tree. If the changes to the Linux kernel are bug fixes that are considered important enough, a pull request for the patches will be sent to Torvalds within a few days. Otherwise, a pull request will be sent to Torvalds during the next merge window. The merge window usually lasts two weeks and starts immediately after the release of

5304-503: The suffix -next for trees containing code which they mean to submit for inclusion in the next release cycle. As of January 2014 , the in-development version of Linux is held in an unstable branch named linux-next . The 20th anniversary of Linux was celebrated by Torvalds in July 2011 with the release of version 3.0.0. As 2.6 had been the version number for 8 years, a new uname26 personality that reports 3.x as 2.6.40+x had to be added to

5382-524: The system device into memory starting at location 1000") to be carried out, effectively loading a small number of boot loader instructions into memory; a completion signal from the I/O device may then be used to start execution of the instructions by the CPU. Smaller computers often use less flexible but more automatic boot loader mechanisms to ensure that the computer starts quickly and with a predetermined software configuration. In many desktop computers, for example,

5460-461: The system functionality is limited until the operating system kernel and drivers are transferred and started. As a result, once the ROM-based booting has completed it is entirely possible to network boot into an operating system that itself does not have the ability to use the network interface. Linux kernel mainline The Linux kernel is a free and open source , UNIX-like kernel that

5538-407: The vanilla branch, and they usually include all fixes from the relevant stable branch, but at the same time they can also add support for drivers or features which had not been released in the vanilla version the distribution vendor started basing its branch from. The community of Linux kernel developers comprises about 5000–6000 members. According to the "2017 State of Linux Kernel Development",

5616-444: The various corporations who use and contribute to Linux, as well as by the various independent contributors out there. It's those people who own the resources who decide... Notable conflicts among Linux kernel developers: Prominent Linux kernel developers have been aware of the importance of avoiding conflicts between developers. For a long time there was no code of conduct for kernel developers due to opposition by Torvalds. However,

5694-949: The version number, it was the first version considered suitable for a production environment . In June 1996, after release 1.3, Torvalds decided that Linux had evolved enough to warrant a new major number, and so labeled the next release as version 2.0.0. Significant features of 2.0 included symmetric multiprocessing (SMP), support for more processors types and support for selecting specific hardware targets and for enabling architecture-specific features and optimizations. The make *config family of commands of kbuild enable and configure options for building ad hoc kernel executables ( vmlinux ) and loadable modules. Version 2.2, released on 20 January 1999, improved locking granularity and SMP management, added m68k , PowerPC , Sparc64 , Alpha , and other 64-bit platforms support. Furthermore, it added new file systems including Microsoft 's NTFS read-only capability. In 1999, IBM published its patches to

5772-700: The word 'hug'. Developers who feel treated unfairly can report this to the Linux Foundation Technical Advisory Board. In July 2013, the maintainer of the USB 3.0 driver Sage Sharp asked Torvalds to address the abusive commentary in the kernel development community. In 2014, Sharp backed out of Linux kernel development, saying that "The focus on technical excellence, in combination with overloaded maintainers, and people with different cultural and social norms, means that Linux kernel maintainers are often blunt, rude, or brutal to get their job done". At

5850-563: The world's largest software and hardware vendors. Version 4.1 of Linux, released in June 2015, contains over 19.5 million lines of code contributed by almost 14,000 programmers. Linus Torvalds announced that kernel version 4.22 would instead be numbered 5.0 in March 2019, stating that "'5.0' doesn't mean anything more than that the 4.x numbers started getting big enough that I ran out of fingers and toes." It featured many major additions such as support for

5928-445: Was agreed upon that each kernel subsystem maintainer would document the rules for patch acceptance. Linux is evolution, not intelligent design ! The kernel source code, a.k.a. source tree, is managed in the Git version control system – also created by Torvalds. As of 2021 , the 5.11 release of the Linux kernel had around 30.34 million lines of code. Roughly 14% of the code is part of

6006-487: Was driven by programmers and testers across the world. With the support of the POSIX APIs, through the libC that, whether needed, acts as an entry point to the kernel address space, Linux could run software and applications that had been developed for Unix. On 19 January 1992, the first post to the new newsgroup alt.os.linux was submitted. On 31 March 1992, the newsgroup was renamed comp.os.linux . The fact that Linux

6084-559: Was revisited in October 2008 by Amanda McPherson, Brian Proffitt, and Ron Hale-Evans. Using David A. Wheeler's methodology, they estimated redevelopment of the 2.6.25 kernel now costs $ 1.3bn (part of a total $ 10.8bn to redevelop Fedora 9). Again, Garcia-Garcia and Alonso de Magdaleno from University of Oviedo (Spain) estimate that the value annually added to kernel was about €100M between 2005 and 2007 and €225M in 2008, it would cost also more than €1bn (about $ 1.4bn as of February 2010) to develop in

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