Der Autor Robert Love sagt selbst zu seinem Buch, daß es sich an Software-Entwickler richtet, die den Linux-Kernel besser verstehen möchten (Zitat S. 24). Der Kernel[Bearbeiten | Quelltext bearbeiten]. Struktur des Linux-Kernels im Detail. → Hauptartikel: Linux (Kernel). Die Linux kernel Development Community (Linux - Kernel - Entwicklergemeinschaft) open source library f Exkurs: Alles, was ich gerade gesagt habe, war.
Linux KernelDie Linux kernel Development Community (Linux - Kernel - Entwicklergemeinschaft) open source library f Exkurs: Alles, was ich gerade gesagt habe, war. Der Linux Kernel wird laufend weiter entwickelt und erweitert. Dieser Artikel liefert einen Überblick über die wichtigsten Neuerungen der. Anschließend bindet der Kernel den Datenträger mit der Linux-Installation ein und ruft das dort liegende Init-System auf. Das startet dann mithilfe des Kernels.
Linux Kernel Different Types of Kernels VideoSyscalls, Kernel vs. User Mode and Linux Kernel Source Code - bin 0x09 Linux kernel sees Btrfs enjoying numerous performance enhancements. And with the addition of more support of NVMe for SSD devices, file system performance on servers should be much. The Linux Kernel documentation¶. This is the top level of the kernel’s documentation tree. Kernel documentation, like the kernel itself, is very much a work in progress; that is especially true as we work to integrate our many scattered documents into a coherent whole. This makes the process seem as it is the sole process running on the machine. The kernel is also responsible for preventing and mitigating conflicts between different processes. This schematically represented below: Figure: Virtual Resources for each Process. The Core Subsystems of the Linux Kernel are as follows. Linux kernel ===== There are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. The Linux® kernel is the main component of a Linux operating system (OS) and is the core interface between a computer’s hardware and its processes. It communicates between the 2, managing resources as efficiently as possible.
Linux Kernel der 15? - Das könnte Sie auch interessierenIn vielen Mailinglistenaber auch in Foren und im Usenet besteht für jedermann die Möglichkeit, die Diskussionen über Pro7 Sendung Kernel zu verfolgen, sich daran zu beteiligen und auch aktive Beiträge zur Entwicklung zu leisten.
Your machine will require virtualization capabilities to use this feature. If you're using an ARM64 machine, please download the ARM64 package instead.
If you're not sure what kind of machine you have, open Command Prompt or PowerShell and enter: systeminfo find "System Type".
Run the update package downloaded in the previous step. Once the installation is complete, move on to the next step - setting WSL 2 as your default version when installing new Linux distributions.
Skip this step if you want your new Linux installs to be set to WSL 1. For more information, read the article changes to updating the WSL2 Linux kernel , available on the Windows Command Line Blog.
Open PowerShell and run this command to set WSL 2 as the default version when installing a new Linux distribution:. Open the Microsoft Store and select your favorite Linux distribution.
The first time you launch a newly installed Linux distribution, a console window will open and you'll be asked to wait for a minute or two for files to de-compress and be stored on your PC.
Learn more. Install Windows Terminal. You can check the WSL version assigned to each of the Linux distributions you have installed by opening the PowerShell command line and entering the command only available in Windows Build or higher : wsl -l -v.
You can change back to WSL 1 at anytime by running the same command as above but replacing the '2' with a '1'. The update from WSL 1 to WSL 2 may take several minutes to complete depending on the size of your targeted distribution.
If you are running an older legacy installation of WSL 1 from Windows 10 Anniversary Update or Creators Update, you may encounter an update error. Follow these instructions to uninstall and remove any legacy distributions.
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Latest commit. Merge branch 'akpm' patches from Andrew. Git stats , commits. The even vs. While the time-frame is open for the development of the next major , the -rcN suffix is used to identify the n'th release candidate for the next version.
Occasional updates to stable releases are identified by a three numbering scheme e. Version 1. After version 1. The major feature of 2. Starting with version 2.
Version 2. Development for 2. Among the changes that have been made in the 2. Also notable are the addition of a wide selection of file systems starting with the 2.
In 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.
Linux used to be maintained without the help of an automated source code management system until, in , development switched to BitKeeper.
It was freely available for Linux developers but it was not free software. In , because of efforts to reverse-engineer it, the company which owned the software revoked the support of the Linux community.
In response, Torvalds and others wrote Git. The new system was written within weeks, and in two months the first official kernel made using it was released.
Details on the history of the 2. The 20th anniversary of Linux was celebrated by Torvalds in July with the release of the 3. Version 3.
Absolutely nothing. On 11 December , Torvalds decided to reduce kernel complexity by removing support for i processors, making the 3.
The numbering change from 2. The major version number was increased to avoid large minor numbers. In April , Torvalds released kernel version 4.
A total of 1, developers, of whom are first collaborators, added more than , lines of code to version 5.
Most websites run on Linux-based operating systems   and all of the world's most powerful supercomputers use some kind of OS based on Linux.
Linux distributions bundle the kernel with system software eg. Android , which accounts for the majority of the installed base of all operating systems for mobile devices,    is responsible for the rising usage of the Linux kernel,  together with its wide use in a large variety of embedded devices.
Linux is a monolithic kernel with a modular design e. Unlike standard monolithic kernels, device drivers are easily configured as modules , and loaded or unloaded while the system is running and can also be pre-empted under certain conditions in order to handle hardware interrupts correctly and to better support symmetric multiprocessing.
The hardware is represented in the file hierarchy. Linux is a clone of UNIX, and aims towards POSIX and Single UNIX Specification compliance.
In order to be included in the official kernel, the code must comply with a set of licensing rules. The Linux Application binary interface ABI between the kernel and the user space has four degrees of stability stable, testing, obsolete, removed ;  however, the system calls are expected to never change in order to not break the userspace programs that rely on them.
Loadable kernel modules LKMs , by design, cannot rely on a stable ABI. In-tree drivers that are configured to become an integral part of the kernel executable vmlinux are statically linked by the building process.
There is also no guarantee of stability of source-level in-kernel API  and, because of this, device drivers code, as well as the code of any other kernel subsystem, must be kept updated with kernel evolution.
Any developer who makes an API change is required to fix any code that breaks as the result of their change. The set of the Linux kernel API that regards the interfaces exposed to user applications is fundamentally composed of UNIX and Linux-specific system calls.
System calls can only be invoked by using assembly instructions which enable the transition from unprivileged user space to privileged kernel space in ring 0.
For this reason, the C standard library libC acts as a wrapper to most Linux system calls, by exposing C functions that, only whether it is needed,  can transparently enter into the kernel which will execute on behalf of the calling process.
Pseudo filesystems e. Because of the differences existing between the hundreds of various implementations of the Linux OS, executable objects, even though they are compiled, assembled, and linked for running on a specific hardware architecture that is, they use the ISA of the target hardware , often cannot run on different Linux Distributions.
This issue is mainly due to distribution-specific configurations and a set of patches applied to the code of the Linux kernel, differences in system libraries, services daemons , filesystem hierarchies, and environment variables.
The main standard concerning application and binary compatibility of Linux distributions is the Linux Standard Base LSB.
The parts of the LSB largely relevant to the kernel are the General ABI gABI ,  especially the System V ABI   and the Executable and Linking Format ELF ,   and the Processor Specific ABI psABI , for example the Core Specification for X There are several kernel internal APIs utilized between the different subsystems.
Some are available only within the kernel subsystems, while a somewhat limited set of in-kernel symbols i.
Linux provides in-kernel APIs that manipulate data structures e. The Linux developers choose not to maintain a stable in-kernel ABI.
Linux creates processes by means of the clone 2 or by the newer clone3 2  system calls. Depending on the given parameters, the new entity can share most or none of the resources of the caller.
In this latter case the new entity owns the same TGID of the calling process and consequently has also the same PID in userspace. The Linux kernel provides the futex 7 acronym for "Fast user-space mutexes" mechanisms for fast user-space locking and synchronization;  the majority of the operations are performed in userspace but it may be necessary to communicate with the kernel using the futex 2 system call.
A very special category of threads is the so-called kernel threads. They must not be confused with the above-mentioned threads of execution of the user's processes.
Kernel threads exist only in kernel space and their only purpose is to concurrently run kernel tasks.
Differently, whenever an independent process is created, the syscalls return exactly to the next instruction of the same program, concurrently in parent process and in child's one i.
Different return values one per process enable the program to know in which of the two processes it is currently executing. Depending on the effective user id euid , and on the effective group id egid , a process running with user zero privileges root , the system administrator, owns the identifier 0 can perform everything e.
Capabilities 7 divides the privileges traditionally associated with superuser into distinct units, which can be independently enabled and disabled by the parent process or dropped by the child itself.
Linux enables different scheduling classes and policies. Linux provides both user preemption as well as full kernel preemption.
With user preemption, the kernel scheduler can replace the current process with the execution of a context switch to a different one that therefore acquires the computing resources for running CPU, memory, and more.
It makes it according to the CFS algorithm in particular it uses a variable called vruntime for sorting processes , to the active scheduler policy and to the processes relative priorities.
With kernel preemption, the kernel can preempt itself when an interrupt handler returns, when kernel tasks block, and whenever a subsystem explicitly calls the schedule function.
Memory management in Linux is a complex topic. First of all, the kernel is not pageable i. In the kernel there is no memory protection no SIGSEGV signals, unlike in userspace , therefore memory violations lead to instability and system crashes.
The first port was performed on the Motorola platform. The modifications to the kernel were so fundamental that Torvalds viewed the Motorola version as a fork and a "Linux-like operating system".
The first Linux that, in a single source tree, had code for more than i alone, supported the DEC Alpha AXP bit platform. Linux has also been ported to various handheld devices such as Apple's iPhone 3G and iPod.
In , the LKDDb project has been started to build a comprehensive database of hardware and protocols known by Linux kernels. Later in the Linux Hardware project was launched to automatically collect a database of all tested hardware configurations with the help of users of various Linux distributions.
Rebootless updates can even be applied to the kernel by using live patching technologies such as Ksplice , kpatch and kGraft.
Minimalistic foundations for live kernel patching were merged into the Linux kernel mainline in kernel version 4.
Those foundations, known as livepatch and based primarily on the kernel's ftrace functionality, form a common core capable of supporting hot patching by both kGraft and kpatch, by providing an application programming interface API for kernel modules that contain hot patches and an application binary interface ABI for the userspace management utilities.
Kernel bugs present potential security issues. For example, they may allow for privilege escalation or create denial-of-service attack vectors.
Over the years, numerous bugs affecting system security were found and fixed. Capabilities 7 have already been introduced in the section about the processes and threads.
Android makes use of them and Systemd gives administrators detailed control over the capabilities of processes. Linux offers a wealth of mechanisms to reduce kernel attack surface and improve security which are collectively known as the Linux Security Modules LSM.
SELinux is now actively developed and maintained on GitHub. Another security feature is the Seccomp BPF SECure COMPuting with Berkeley Packet Filters which works by filtering parameters and reducing the set of system calls available to user-land applications.
Critics have accused kernel developers of covering up security flaws or at least not announcing them; in , Linus Torvalds responded to this with the following:  .
I personally consider security bugs to be just "normal bugs". I don't cover them up, but I also don't have any reason what-so-ever to think it's a good idea to track them and announce them as something special It makes "heroes" out of security people, as if the people who don't just fix normal bugs aren't as important.
In fact, all the boring normal bugs are way more important, just because there's[sic] a lot more of them. I don't think some spectacular security hole should be glorified or cared about as being any more "special" than a random spectacular crash due to bad locking.
Linux distributions typically release security updates to fix vulnerabilities in the Linux kernel. Many offer long-term support releases that receive security updates for a certain Linux kernel version for an extended period of time.
The community of Linux kernel developers comprises about members. According to the " State of Linux Kernel Development", a study issued by the Linux Foundation, covering the commits for the releases 4.
As of companies, the top contributors are Intel Instead of a roadmap, there are technical guidelines. The resources are all owned by 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 The Linux development community uses Git to manage the source code. Git users clone the latest version of Torvalds' tree with git-clone 1  and keep it up to date using git-pull 1.
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 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.
A developer who wants to change the Linux kernel starts with developing and testing that change. Depending on how significant the change is and how many subsystems it modifies, 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 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 the previous kernel version.
Since all the code must adhere to the 21 rules comprising the Linux Kernel Coding Style. The GNU Compiler Collection GCC or GNU cc is the default compiler for the mainline Linux sources and it is invoked by a utility called make.
Then, the GNU Assembler more often called GAS or GNU as outputs the object files from the GCC generated assembly code.
Finally, the GNU Linker GNU ld is used to produce a statically linked executable kernel file called vmlinux. The above-mentioned tools are collectively known as the GNU toolchain.
GCC was for a long time the only compiler capable of correctly building Linux. In , Intel claimed to have modified the kernel so that its C compiler was also capable of compiling it.
Since , effort has been underway to build Linux with Clang , an alternative compiler for the C language;  as of 12 April , the official kernel could almost be compiled by Clang.
By enabling Linux to be compiled by Clang, developers may benefit from shorter compilation times. In , developers completed upstreaming patches to support building the Linux kernel with Clang in the 4.
Google's Pixel 2 shipped with the first Clang built Linux kernel,  though patches for Pixel 1st generation did exist.
Google moved its production kernel used throughout its datacenters to being built with Clang in Linux bugs can be very hard to find out and fix, firstly because of kernel interaction with userspace and hardware and secondly because they might be caused from a wider number of reasons than those which can affect user programs.
A few examples of the underlying causes are semantic errors in code, misuse of synchronization primitives, and an incorrect hardware management.
ORC unwinder Zero Page The TLB MTRR Memory Type Range Register control PAT Page Attribute Table Linux IOMMU Support Intel R TXT Overview AMD Memory Encryption Page Table Isolation PTI Microarchitectural Data Sampling MDS mitigation The Linux Microcode Loader User Interface for Resource Control feature TSX Async Abort TAA mitigation USB Legacy support