The kernel of operating systems popularly known as Linux, or sometimes GNU/Linux.

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How can I find the implementations of Linux kernel system calls?

I am trying to understand how a function, say mkdir, works by looking at the kernel source. This is an attempt to understand the kernel internals and navigate between various functions. I know mkdir ...
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3answers
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What does the Windows flag in the Linux logo of kernel 3.11 mean?

I've just installed kernel-3.11.0-1.fc20 for my Fedora 19 installation. During the rebooting progress, I saw the Linux logo with a Windows flag in it, what does it mean? The Fedora 19 is installed ...
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Why isn't Linux embraced as the official GNU kernel?

While I knew for quite some time the existence of Hurd, and its mission as the official GNU Operating System kernel, I was wondering how come Linux is not embraced as the official GNU kernel over the ...
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Why is the Linux kernel called an “image”?

I often hear people refer to the Linux kernel as the Linux kernel image and I can't seem to find an answers on any search engines as to why its called an image. When I think of an image I can only ...
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Why does mount require root privileges?

Why does Linux require that a user be root/using sudo/specifically authorized per mount in order to mount something? It seems like the decision as to whether to allow a user to mount something should ...
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Does the kernel have a main() function? [closed]

I am learning device drivers and Kernel programming. According to Jonathan Corbet's book, there is no main() function in device drivers. So I two questions: Why don't we need a main() function in ...
34
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Linux Kernel: Good beginners' tutorial [closed]

I'm interested in modifying the kernel internals, applying patches, handling device drivers and modules, for my own personal fun. Is there a comprehensive resource for kernel hacking, intended for ...
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2answers
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Why did powering down my machine after a bad `rm` save my files?

Classical situation: I ran a bad rm and realized immediately afterwards that I had removed the wrong files. (Nothing critical and I had tolerably recent backups, but still annoying.) Knowing that ...
26
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1answer
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What would be the best way to work around this glibc problem?

I administer a Gentoo Hardened box that uses file capabilities to eliminate most of the need for setuid-root binaries (e.g. /bin/ping has CAP_NET_RAW, etc). Infact, the only binary I have left is ...
24
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1answer
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High CPU usage with CFS?

I asked a previous question to try and isolate the source of an increase in CPU usage when moving an application from RHEL 5 to RHEL 6. The analysis that I did for that seems to indicate that it is ...
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Linux: How to find the device driver used for a device?

If my target has one device connected and many drivers for that device loaded, how can I understand what device is using which driver?
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Configuring, compiling and installing a custom Linux kernel

I'd like to try using a kernel other than the one provided by my distro -- either from somewhere else, or as customized by me. Is this difficult or dangerous? Where do I start?
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How to get started writing drivers?

I have a throw-away cheap laptop I'd like to twiddle around, a Thinkpad SL 500. What bothers me are two leds, the one for wireless connectivity, and the one for hibernation, which don't light up at ...
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2answers
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What is the purpose of patches of the linux kernel?

For each Linux kernel version, there is a patch file available for download. For instance, linux-3.12.22 has a corresponding patch-3.12.22. What is the purpose of that patch? To always patch the ...
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3answers
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How to tell Linux Kernel > 3.0 to completely ignore a failing disk?

I am asking this question here in the hope that some Linux-kernel guru can have an answer. This question has been asked on AskUbuntu and on SuperUser without answers: thinking better, it is really ...
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Is it possible to install the linux kernel alone?

I'm just curious if it's possible to install the linux kernel alone, or if you need to use one of the flavours. If it were possible, how would you do it? I don't need a detailed tutorial. I just want ...
17
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1answer
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Linux: What is a tainted kernel?

Under certain conditions, the Linux kernel may become tainted. For example, loading a proprietary video driver into the kernel taints the kernel. This condition may be visible in system logs, kernel ...
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Who is responsible for the Linux kernel?

As of today, there are many Linux distributions like Ubuntu, Fedora, Gentoo, Mint, Debian, etc. These distributions update at different cycles. Ubuntu seems to update its kernel weekly or monthly, ...
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1answer
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How to display kernel command line parameters?

In the grub.conf configuration file I can specify command line parameters that the kernel will use, i.e.: kernel /boot/kernel-3-2-1-gentoo root=/dev/sda1 vga=791 After booting a given kernel, is ...
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Can ps display only non kernel processes on Linux?

How can I ask ps to display only user processes and not kernel threads? See this question to see what I mean...
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Can I create a virtual ethernet interface named eth0?

I am running Arch based on the Linux 3.10.5-1 kernel. The system uses the new de-facto naming conventions of ethernet interfaces enp*s* and wlp* etc. This is a problem however, as my educational ...
16
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2answers
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The UEFI & SecureBoot impact, how severe?

I'm planning to buy a new laptop in the coming days, and I'm quite impressed with new, cool Ultrabooks. As a long-time GNU/Linux user, I'll of course install a distro of my choice on it. Chances are ...
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Does Android really use the same kernel as Linux?

I read from somewhere that Android uses the Linux Kernel. Is it really true? I thought the Linux Kernel was meant for desktop operating systems.
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1answer
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What happens in each step of the Linux kernel-building process?

I've read many tutorials about how to build custom kernels and boot Ubuntu using those kernels, and successfully followed the guides and booted custom kernels, but I have no understanding about what ...
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3answers
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Given a git patch id, how to find out which kernel release contains it?

Assume I have some issue that was fixed by a recent patch to the official Linux git repository. I have a work around, but I’d like to undo it when a release happens that contains my the fix. I know ...
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kernel: Namespaces support

I am wondering what exactly the “Namespaces support” feature in the Linux kernel means. I am using kernel 3.11.1 (the newest stable kernel at this time). If I decide to disable it, will I notice any ...
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Setting CPU governor to on demand or conservative

I'm struggling with cpupower on ArchLinux. I want to set governor to ondemand or even to conservative. First if I do $ sudo cpupower frequency-info --governors, I only get performance powersave. So ...
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Linux on a 286?

I don't own a 286 nor do I intend to run Linux on one. However since the 286 has protected mode, why is it frequently stated that Linux requires a 386 CPU or higher? From ...
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Why there are many BSD systems but only one Linux kernel?

Why there are many BSD systems but only one Linux kernel? I wonder why BSD was forked many times, but no such thing with Linux.
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How many actual developers work on the Linux Kernel

For a study I am doing I was asked how many actual developers commit on a typical kernel version. I know there is Linus Torvalds as the main developer, followed by many second main developers. ...
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Using real time kernel headers to compile userspace code vs default headers

Per customer requirements, I installed CentOS 5.6 with the default kernel. With this kernel installed, the time.h file includes the #define CLOCK_MONOTONIC. Now, a real-time kernel was installed ...
11
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Are FIFO, pipe & Unix domain socket the same thing in Linux kernel?

I heard that FIFOs are named pipes. And they have exactly the same semantics. On the other hand, I think Unix domain socket is quite similar to pipe (although I've never made use of it). So I wonder ...
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What does a niceness value of (-) mean?

According to the man page, and wikipedia; nice ranges from -20 to 20. Yet when I run the following command, I find some processes have a non numerical value such as (-). See the sixth column from ...
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Observing a hard-disk write in kernel space (with drivers/modules)

Apologies in advance if this post is a bit dense/messy, but I'm having a hard time formulating it better... Basically, I would like to study what happens upon a hard disk write, and I'd like to know: ...
11
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How to boot EFI kernel using QEMU (kvm)?

Hey guys I'm trying to emulate a EFI enviroment using QEMU (kmv), virtualbox takes 15 minutes to boot in EFI mode using archboot. Using legacy BIOS mode I can boot using this command: ...
11
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Enabling IOMMU in the kernel for graphics card pass-through

Short question: How can I turn on the intel_iommu setting in the Linux kernel? I run a Debian host, using the grub2 bootloader. Documentation I've seen says to edit /boot/grub/menu.lst, which seems ...
10
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enabling numa for Intel Core i7

In Linux kernel, the documentation for CONFIG_NUMA says: Enable NUMA (Non Uniform Memory Access) support. he kernel will try to allocate memory used by a CPU on the local memory controller of the ...
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using devtmpfs for /dev

I have noticed the following option in the kernel: CONFIG_DEVTMPFS Device Drivers -> Generic Driver Options -> Maintain devtmpfs to mount at /dev And I see that it is enabled by default in ...
10
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1answer
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Load Linux bzImage in QEMU?

I compiled a Linux by doing make menuconfig then make and now I have compiled the most recent version of Linux. How can I load the kernel into QEMU?
10
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How does the system shutdown of a linux kernel work internally?

I have somehow an rough idea of how the userspace and init-system (be it classic init sysV /upstart/ systemd) work at system shutdown. (Essentially there is an order succession of "Stop!", "Please ...
10
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Possible to see dead proccesses?

In man ps, it clearly states the different states a process can have on Linux. D Uninterruptible sleep (usually IO) R Running or runnable (on run queue) S Interruptible sleep (waiting for an ...
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When do I need to specify add_efi_memmap as kernel argument in UEFI/EFI boot?

I am reading some tutorials how to EFI stub (efistub) load the Linux kernel. These instructions often use kernel boot parameter add_efi_memmap. The intended hardware is Intel x64 having 8GB of RAM. My ...
9
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1answer
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In what sense does SATA “talk” SCSI? How much is shared between SCSI and ATA?

This is nothing new to me at least, that SATA actually "talks" SCSI, hence why these SATA devices show up as SCSI devices in Linux. A related question has been asked before, e.g. Why do my SATA ...
9
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Why does the Linux kernel report “out of disk space” when in reality it is out of i-nodes

A friend of mine who likes programming in the Linux environment, but doesn't know much about the administration of Linux recently ran into a problem where his OS (Ubuntu) was reporting "out of disk ...
9
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1answer
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Understand logging in Linux

As I understand, Linux kernel logs to /proc/kmsg file(mostly hardware-related messages) and /dev/log socket? Anywhere else? Are other applications also able to send messages to /proc/kmsg or /dev/log? ...
9
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2answers
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How do I get a linux kernel patch set from the mailing list?

I don't subscribe to the linux-kernel mailing list, but I want to get a set of patches that were posted a few weeks ago and apply them to my kernel for testing. I'm very familiar with patching, ...
9
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1answer
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How is nice working?

sched_setscheduler says : All scheduling is preemptive: if a process with a higher static priority becomes ready to run, the currently running process will be preempted and ...
9
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Isolating cause of higher CPU usage on RHEL 6 vs RHEL 5

I'm currently looking to move our system from RHEL 5 to RHEL 6, but I've run into a snag with unexpectedly high CPU usage on the RHEL 6 machines. It appears that this may be due at least in some part ...
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Linux kernel dropping custom keyboard scan codes

I have a vintage IBM 122 key model M keyboard that I am adapting for use on a modern computer. I am using a Teensy 2.0 to do the encoding and to handle the USB side of things. I borrowed the firmware ...
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How exactly does printk work internally?

I know printf needs help from the OS to do its job. I also know printf does not work in the Linux source code as there is no library. And so we have printk for debugging. How does printk work ...