Everything about UNIX kernels: development, configuration, compilation, design, etc.

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Kernel bug at at fs/dcache.c on XenServer

Yesterday on of our servers running Xen 6.5 restarted, in /var/log/messages I found following messages: Apr 29 11:52:59 server kernel: [7476681.051566] ------------[ cut here ]------------ Apr 29 11:...
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Dracut failure when trying to boot Fedora with Qubes kernel

I would like to boot Fedora 23 Workstation x86_64 with a kernel from QubesOS 3.1. I have copied vmlinuz-4.1.13-9.pvops.qubes.x86_64 and initramfs-4.1.13-9.pvops.qubes.x86_64.img into the /boot ...
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Designing a new Operation System

I want to design a new OS to learn more about how an OS works. This OS is only for educational purpose and I had a few doubts choosing its kernel. Is there any legal issue for using an Ubuntu kernel?...
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How filesystem atomically writes a block to disk?

Block is an abstraction provided by filesystem, block size is integer multiples of disk sector size. Suppose a filesystem uses 4K as its block size, and the disk sector size is 512B, when the ...
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Home directory does not mount on kernel update

My home directory will not mount on booting with new linux kernel. Previously, my home directory has been mounted automatically from a network device. I updated my kernel to 4.6.0 from the git ...
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How do I enable higher C-states on Xeon 1505m with Linux?

I am running a Lenovo ThinkPad P70 with a Xeon E3-1505M v5. Installed the 201604 Arch, most everything is running well, except power states. The kernel I'm using is 4.5.1-ARCH, but I've also tried 4.6 ...
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How do I compute the angle of the 2D 3 points ? [[ In kernel space]

I 'm looking at the touch driver 's Kennel. Sometimes a touch is bouncing County singah appear. Collected by recruiting three points 'm trying to calculate the angle between . But there is no such ...
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How to support 64-bit times on a 32-bit Linux platform

I need to support 64-bit times on a 32-bit ARM embedded Linux system based on kernel version 4.1. I use clock_gettime() and clock_settime() to get/set the time, but they are limited to 32-bit seconds ...
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Kernel problem after upgrading to 4.5.1

I updated my kernel from 3.19 to 4.5.1 (which is the latest ubuntu-based upgrade), and when I rebooted, I saw an alert: Alert! /dev/disk/by-uuid/xxxxxxxxxxxxxxxxxxx does not exist! where x's are ...
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ALG IPSEC and RSTP

I have linux 3.18. my Linux is installet on a router. in this router I activate a NAT from the wan side. Does this Linux support ALG of IPSEC and RSTP ?
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How to use the proper video driver on Scientific Linux 6 for Display Port screens?

I am working with (one of) my workstation(s) working under Scientific Linux 6, so, basically a quite old version of Red Hat Enterprise Linux. I would need to use 2 screens, but only have 2 DisplayPort ...
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Installing Wireless Adapter (GWU625 v1.1) On Modern Fedora OS

I am trying to install the driver to GWU625 v1.1. You can download it here for what it is worth. It is recommended for Fedora v10 but I want a to run an OS which is supported by the people who ...
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1answer
23 views

Are IPv6 link-local addresses assigned by the kernel or by a userspace program

When IPv6 is enabled for an interface, it will get a link-local address assigned automatically based on the MAC of the network interface. But who assigns this address? Is it done in the kernel, or by ...
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29 views

What is kernel Space and User space. [duplicate]

what is Kernel space ? i want to understand it and same with User space and what is the diff between them
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How to block drivers built-into Kernel, i.e. drivers who are not a module

I configured and compiled Linux kernel with nouveau driver built-into kernel, i.e. with <*> as opposed to <M> when doing make menuconfig inside Linux kernel source directory. Now, I ...
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How to compile custom kernel for Raspberry Pi

I'm trying to run the Ubuntu 14 Raspberry Pi ARM image in QEMU, and for that I need the kernel that matches the version used in the image. If I mount the image and run file vmlinuz I see: vmlinuz: ...
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How is redirection implemented?

Is redirection a concept of the shell, not of the OS kernel? How is redirection implemented in terms of system calls? Is redirection implemented similarly to pipe?
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Filesystem kernel API

Assuming that all filesystems are specific, how tools like ls, touch, cat, etc interacting with them? I suppose that 'ls' doesn't know specifics about btrfs for example, but it reads directory entries ...
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Cleaning swap space while running

I have a theoretical question, What would happen if I clean up all the swap space while running, Would the operating system crash because of page faults that would happen in the kernel?
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m2c : Command not found

I want to experiment on DCTCP protocol. For that I am trying to compile linux kernel version 3.2.18 and include a dctcp patch for that. I am following the directions given here. While I am compiling ...
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154 views

Error on enabled probe: syscall::open_nocancel:entry): invalid user access in action #2 at DIF

I've the following one-liner to show files opened by process: sudo dtrace -n 'syscall::open*:entry { printf("%s %s",execname,copyinstr(arg0)); }' however I've plenty of repeated errors such as: ...
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minimum time between two consecutive UDP packets

I am interested in developing a C application which sends UDP packets with minimum delay between two consecutive packets. Is it possible to "book" the UDP stack with the NIC hardware from user space ...
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Change Wireless adapter driver in Linux

I am using openSUSE Tumbleweed. I've bought a new PCI-E Wireless card, that supports 5G WiFi (Intel 5100 AGN). It doesn't show up in lspci and even if I take old adapter out it still cannot see my ...
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Linux usb-drive write cache

Is there any way to change the way the Linux kernel handles external storage and the external storage cache? Every time I copy something to it, the copy process seen from userspace seems really fast. ...
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it terms of terminology is there an accepted difference between a kernel agent and a kernel module or a kernel driver?

In terms of terminology is there an accepted difference between the concept of a kernel agent, kernel module, or a kernel driver?
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Userspace Network Stack

I am writing a (very simple) userland IP network stack. For this purpose, I need to go "around" the OS network stack and obtain the raw Ethernet frames. The tap interface sounds like a way to go, but ...
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dracut-initqueue: Could not boot, /dev/disk/by-uuid does not exist

I've just installed second linux kernel on my machine and after the boot, I'm getting following error: dracut-initqueue: Could not boot [Warning] /dev/disk/by-uuid/943eb4bb-be3f-4252-83e9-...
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How to verify NX usage in Linux kernel?

I'd like to verify that the current system is using NX bit protection somehow. I know that this can be done by checking the initial lines in the dmesg output. But that's a rolling buffer, so I'm not ...
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How to uninstall linux kernel?

I was building linux kernel from git master for ubuntu all day, I was not able to build packages, so I just ran sudo make module_install install. How to remove it? Makefile doesn't provide make ...
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1answer
144 views

How does a bootloader actually hand off to a kernel?

Assume I have a bootloader with a kernel and initrd line. For all intents and purposes, I now have 2 or 3 stages of "kernel" going on: firmware grub (or other bootloader) actual linux kernel The ...
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1answer
66 views

How to simulate GPU hardware failure?

I'm doing some research that has to do with GPGPU resilience with NVIDIA graphics cards and I've been looking for a way to, as accurately as possible, simulate hardware failure. I know about ...
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How to know when I could reactivate HWP (Hardware PStates)

I have a x1 carbon 4gen, and my computer hangs during boot on "HWP enabled" message. For now the solution is to disable HWP (Hardware PStates) with the option intel_pstate=no_hwp on boot. There is a ...
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Kernel make install error for RTAI 3.8 on CentOS 6.5

Before posting I have read almost every similar post I could find on this and other websites but I haven't found an useful answer. I have to install a custom software that needs RTAI 3.8 on top of ...
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is there a description for kernel messages?

I use dmesg to output kernel messages, but since I'm new to linux I have no idea what this informations mean. Is there a good tutorial or description so I can understand the messages. for example: ...
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Mouse button stops working intermittently

I have noticed that I'm not the only one with mouse button problems. This problem seems to affect multiple users on many different Linux versions regardless of Desktop versions (at least in Unity &...
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How to trace the life cycle of kernel threads by following creation and switching?

How to trace the life cycle of kernel threads by following creation and switching ? kernel_thread() and schedule() are the 2 functions I know that but have no idea how to implement it..
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Why can't I find kernel headers on CentOS 7 when trying to install VirtualBox Guest Additions?

I have a minimal CentOS 7 installation as a VirtualBox 5.0.16 r105871 guest on a Windows 8.1 host. uname -r reports "3.10.0-327.10.1.el7.x86_64". When I try to run VBoxLinuxAdditions.run I get an ...
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Difference between symlimk and link? [duplicate]

What is the difference between a "symlink" and a "link".
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89 views

What step am I missing to get my 2.6 ARM kernel running in QEMU?

I am trying to cross-compile and boot a Linux 2.6 kernel for ARM using QEMU. I have basically followed the same instructions that are included in seemingly every single tutorial on the topic. ...
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Raspbian Kernel Oops at fs/dcache.c

We have a Raspberry Pi 2 running Raspbian 8 Jessie. We are running a simple Python 3 based Flask server to read from GPIO pins and toggle a relay (Externally powered). This system is polled every ...
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Ubuntu upgrades blocked due to insufficient disk space for linux-image [duplicate]

I am running Ubuntu Server 14.04 LTS on a desktop at my home that I was intending to turn into a server, but I never really did much on it. I then decided to turn it into a send-only SMPT server, but ...
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GMA500 video chip uses mode that monitor can't sync to (even text mode)

I have a new CentOS7 installation which starts fine (I see the Grub2 menu). If I disable RHGB I can even watch bootup to a point - then all video disappears. The OS is booting to runlevel 1 (text ...
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Why can't I run android apps on generic linux? [closed]

I know about projects like archon, and various emulators exist, but it seems strange that I can run windows programs but not android programs under a stock linux kernel.
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2answers
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How to get the absolute position (x, y coordinates) of a finger on a touchpad?

Main question: How to get the absolute finger position on the touchpad? I would like to get the absolute position (x, y coordinates) of a finger on a touchpad? I believe it is possible to extract it ...
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Dynamic mdev ifup and ifdown of network interface

Is it possible to have an mdev.conf rule that would run ifup on device creation and ifdown on detach? i.e. eth[0-9] root:root 660 @ifup $MDEV | $ifdown $MDEV
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How to install kernel 4.4 on debian testing?

Hello can someone tell me how to install kernel 4.4 on current debian testing ? I have a bug that might be solved by the kernel 4.4 so I want to give it a shot but can't find the name of the package ...
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How to interpret perf -e cache-misses:pp?

I find the behavior of perf top -e cache-misses:pp -p <my_pid> quite confusing. I own an Intel i5-3230M, running kernel 4.4.5 64 bit. If I just run that commmand, I get basically no samples ...
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How can I activate extra-verbose mode (debugging mode) during Debian boot?

How do I activate extra verbosity during boot, on Debian? I removed the quiet parameter and tried to add debug but it didn't help. My problem is that my keyboard takes 2-3 min to activate so it ...
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Kernel panic dump analisys

We got a kernel panic today and I think that one scsi device caused it. Can you help me to interpret this output? What does <<EOE>> mean? <0>Kernel panic - not syncing: Watchdog ...
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Build custom EDID with several modelines

I would like to build custom EDID using kernel sources. But I need to use several modelines - more refresh rates for same resolution. Is it possible using method in kernel sources? Could you please ...