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

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understanding “bridge check” hop in packet flow in Linux kernel

According to "Packet flow in Netfilter and General Networking" drawing in Wikipedia Netfilter article: ..one of the first hops in packet flow right after the traffic control and queuing is bridge ...
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Is sysfs a strict subset of procfs? [duplicate]

Is the information that the Linux kernel provides to the user via sysfs a strict subset of the information that the Linux kernel provides to the user via procfs? If not, then which information is ...
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22 views

Does Tails OS have binary blobs in its kernel, and how much does it matter? [on hold]

Tails is a distribution which has maximum privacy as its main goal. It was famously used by Mr. Edward Snowden prior to his leaking of documents. Is this distribution 100% open source, or are the ...
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How does the kernel assign cpu ids to physical cores?

One may find a lot of info about how to inspect physical cores layout in a running linux system, but I'm wondering how the physical cores are assigned a cpu id in the first place. After experiencing ...
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15 views

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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How to run my own Hello World C application on top of stand-alone Linux kernel in x86_64 machine.. [on hold]

I have compiled Linux kernel 4.5.2 & got below files. "vmlinuz-4.5.2" "System.map-4.5.2" "initrd.img-4.5.2" My requirement is very clear, I need to run my own Hello World C application on top of ...
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23 views

Linux is crashing without throwing core dump or error message

I am working on a development board to make custom linux working(built through Yocto) on it. Right now, I am facing very weird issue. System boots and after some time it hangs and restarts without any ...
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44 views

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 ...
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35 views

Building kernel for BeagleBone Black lead me hdmi problems

I have successfully followed CLFS book to build RPi and BBB embedded systems. In RPi case the bootloader did not give me problems with device tree. Some years ago I would have to patch Torvalds' ...
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26 views

Linux Crypto API headers missing

As soon as headers are essential to deal with crypto algorithms, provided by kernel, I've installed linux-headers-4.4.0-1-amd64. However, this did not added files like crypto.h, module.h and init.h ...
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Missing `/dev/sda` when building a minimal kernel for VMware

I'm trying to build a minimal Linux kernel using buildroot that I want to run on VMware, among other platforms. However, when I boot the kernel it doesn't recognize the hard drive (i.e., no /dev/sda). ...
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How to find out which Linux kernel versions are the most prevalent?

I am gearing up to do some scientific experiments that involve modifying the linux kernel to collect data on the internal runtime states of certain modules. We want to do the experiments over a ...
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34 views

How to determine if a custom kernel improves system performance?

In addition to measuring boot time and kernel size before and after re-compilation, what are some other useful metrics for determining if a custom-compiled kernel improves system performance? I know ...
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38 views

kernel: hpet1: lost 19 rtc interrupts

I have this error that flooding my syslog every day. As a solution on arch linux forum is hpet=disable in kernel command line, but I think it is a bad idea and I searching for another solution. Is ...
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Linux:how java applications having 1000 threads are managed by 2 CPU's os?

Linux: 2CPU's, 16gb ram Let's say, for example, tomcat having 1000 threads. How this application threads will be shared between two CPU's, and what is the value of run queue length? In my case when ...
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1answer
18 views

Can module loading be globally disabled on modern Linux kernels?

Once upon a time (before kernel 2.6.25), one could use /proc/sys/kernel/cap-bound to drop CAP_SYS_MODULE system-wide, and be assured that the set of code that was presently loaded into kernel space ...
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8 views

SocketCAN read socket call is blocking [migrated]

I am trying to do a socket read from CAN socket. My read call is getting blocked and never returns control outside. Steps in my code flow: open a socket assign interface name assign CAN ID Assign ...
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Linux: Relation between run queue length and load average [duplicate]

Is there any relation between run queue length and load average?. references appreciated
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Files backing loop devices opened without O_EXCL

Loop devices are the primary way (and perhaps the only way) to treat normal files as block devices in Linux. It's strange that backing files aren't protected by O_EXCL flag. Why is that? Why nobody ...
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16 views

MT7601 WiFi drivers on uClinux

I have an ARM based board running uClinux on it. It had a working ra0 interface (MT7601 WiFi module) before I recompiled and installed new kernel on it. Before writing new kernel and filesystem to it, ...
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1answer
34 views

what is the difference between vmlinuz vs zImage?

What I know (please correct if my understanding is wrong): vmlinuz: is a compressed, self-extracting, bootable Linux image. Always ELF? Generated how? zImage (or bzImage): are compressed, ...
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59 views

NVMe PCIe disk power cycling

I want to test a NVMe SSD that is connected to a PCIe slot of my motherboard. The test procedure is a specific algorithm that writes workloads to the SSD, while the SSD is exposed to radiations (e.g. ...
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1answer
27 views

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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38 views

Is it safe to mount same ext4 filesystem at different mount points?

I know there is option "--bind" for multiple mount operation to handle such case. But ext4 can be directly mounted at different mount points, without option "--bind". So, I wonder whether it is safe ...
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Add TCP congestion control variant to Linux Ubuntu

I want to test different variants of TCP in Linux Ubuntu. I have Ubuntu 14.04 LTS with Kernel version 3.14. When I check the available congestion control algorithm using the following command sysctl ...
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How to play a beep/sound file from the u-boot for Panda-board?

I want to play a Beep/Sound file during the boot up from the u-boot on the speakers connected to panda-board. As this functionality is there in PC ,How to replicate the same on the embedded platform ...
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29 views

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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57 views

switch_root with systemd: “Too many levels of symbolic links”

I'm trying to boot a proprietary kernel build and OS after an upgrade to libc and numerous other tools. I'm booting using an initramfs in the 3.2.0 kernel with some utilities, like busybox. However, ...
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On Linux, when does “uptime” start counting from?

My computer says: $ uptime 10:20:35 up 1:46, 3 users, load average: 0,03, 0,10, 0,13 And if I check last I see: reboot system boot 3.19.0-51-generi Tue Apr 12 08:34 - 10:20 (01:45) ...
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Saving time while compiling Kernel

I have to demonstrate a practical where I have to make my own module, add this module to a kernel's source and implement the system call. I'm using 3.16 kernel on Ubuntu but it takes around 2 hours to ...
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116 views

Linux/compiler-gcc5.h: No such file or directory

I run into problem compiling a kernel scheduler for testing the compiling error linux-2.6.32-rc3/include/linux/compiler-gcc.h:86:30: fatal error: linux/compiler-gcc5.h: No such file or directory ...
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Finding digest of kernel mailing list

I am looking for the digest of the LKML. The Dell site doesn't seem to have it, even though several places link to it. Additionally, googling just comes up with old links. Does the "digest mode" ...
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who has loaded an identity mapped page table?

I want to understand Linux x86_64 's startup steps, after reading some articles and linux-3.14.65/Documentation/x86/boot.txt, and almost know that the first instruction to run in vmlinux is ...
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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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27 views

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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26 views

How to upgrade from Fedora 21 to higher stable version with the highest convenience and safety?

I am still working on a Fedora 21 Linux. I know Fedora 22, 23 and 24 already are around. However being a newbie in Linux systems and given the fact that my friend helped me to install Fedora 21 back ...
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How do I enable memory zone reclaim mode on the Linux kernel?

I am running Gentoo Linux Hardened using kernel 4.3.3-hardened-r4 on an AMD A4-5300 APU. To troubleshoot a memory problem I have with my system I need to enable sysctl vm.zone_reclaim_mode=1, but ...
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Show kernel routing exception entries (FIB)

Linux 3.6 removed the ipv4 routing cache (commit). Changelog says: Remove the ipv4 routing cache. Now lookups go directly into the FIB trie and use prebuilt routes cached there. According to ...
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How Linux handles mouse events at kernel level [duplicate]

I am interested to know how Linux handles mouse events such as movements and pressing a mousebutton. Could one say generally - when the mousebutton is pressed the following happends: just guessing ...
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3answers
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I need a specific kernel version. How do I get the corresponding Debian iso?

Say I need a Debian with Kernel 3.2.63-2+deb7u1 i686. How do I find the corresponding Debian Version? I assume it would be Debian 7 because this document states that Debian 7 has Kernel version 3.2. ...
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How the file “.vmlinux.lds.cmd” is produced?

Recently, I want to know how vmlinux.lds is produced, I found a file called .vmlinux.lds.cmd which has: cmd_arch/x86/kernel/vmlinux.lds := gcc -E -Wp,-MD,arch/x86/kernel/.vmlinux.lds.d -nostdinc ...
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66 views

How to compile kernel module for different kernel version?

I have the following kernel installed: [root@localhost ~]# uname -r 2.6.32-573.el6.x86_64 And the following kernel source: linux-2.6.32-573.1.1.el6.x86_64 I am trying to compile a kernel module ...
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Can I install a .vmlinuz-<version>.hmac for an installed kernel after the fact?

I installed a kernel from elrepo on my asus ux501jw, centos7 os. I have tried the 4.5.0 and the 4.4.6 versions. Both of them do not install the hmac file /boot/.vmlinuz-.hmac file. Concequently the ...
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effective creator PID for each socket in user space for local tcp connection [migrated]

i want to get the creator PID for each socket in user space for local tcp connection, i see in kernel there is support for returing PID with "SO_PEERCRED" ioctl to work across namespaces. it uses ...
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Install GUI :Red Hat Enterprise Linux Server release 7.0 (Maipo)

I am trying to install GUI of Red Hat Enterprise Linux Server release 7.0 (Maipo) as i follow this web page install-gnome-gui-on-rhel-7-linux-server to install GUI but when i run first command ...
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105 views

Avoiding a buggy kernel version with “Oops” in radeon module

I have exactly the same problem as described here. I can find the same "Oops" messages in /var/log/kern.log. I also have an older Radeon HD (so I have to use the free driver). I downloaded the current ...
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How do I write to a __user memory from within the top half of an interrupt handler? [migrated]

I am working on a proprietary device driver. The driver is implemented as a kernel module. This module is then coupled with an user-space process. It is essential that each time the device generates ...
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40 views

cpupower can't be unable to call hardware when it tries to get the current cpu frequency

I tried cpupower on Archlinux, but it always was unable to call hardware when it tries to get the current cpu frequency. # cpupower frequncy-info analyzing CPU 0: driver: intel_pstate CPUs which ...
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Error occured with USB modem

I have MPC8309 Tower Board and connected USB Modem to it and then established Async PPP on Modem, now I started applying ping from different terminal from my laptop by applying nat commands and ...
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Invalid module format

I try to install a module using this command: sudo insmod mymod.ko [arg1] [arg2] but I get this error while loading the module: insmod: error inserting 'mymod.ko': -1 Invalid module format my ...