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

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built-in command prompt without a shell? [on hold]

This is regarding any similarities to the linux/unix kernel with older and simpler operating systems such as MSDOS and Apple DOS 3.3, which had commands built into them and an internal shell always ...
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2answers
34 views

Generate raw Ethernet frames with memory preloaded payloads at < 1 ms intervals

I am looking to generate raw Ethernet frames with payload that is preloaded into memory. The Ethernet frames (10-60 full frames) should be generated at 1 ms intervals with no exception. What would ...
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1answer
43 views

How to study the linux kernel source? [closed]

I have finished studying Operating Systems about a year ago, and now I'm interested in linux. So I plan to study Linux from the source code. But when I look at the source code, it is really big in ...
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Process stuck in kernel code, what is it doing? [closed]

I have a process (db_add) which is stuck is kernel code. This process is the only ressource-intensive process running on the machine. Top reports a 100% (ie it fully uses a single core) CPU usage: ...
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Which components of Linux IO subsystem are device-independent and device-dependent?

From Tanenbaum's Modern OS, every operating system has an I/O subsystem for managing its I/O devices. Some of the I/O software is device independent, that is, applies to many or ...
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What causes a PCI ID to change

When running lspci on my RHEL 7.2 box I noticed my Ethernet Adapters changed PCI bus IDs. In the example below it changed from "02:00.x" to "03:00.x". What might have caused this? Is there a way ...
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Is the entire kernel loaded into memory on boot?

I read through this popular IBM doc (I see it referred quite often on the web) explaining the function of the initial RAM disk. I hit a wall in conceptualizing how this works though. In the doc it ...
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Dereferencing string pointer in ftrace event filter

I'm currently trying to create an ftrace event filter for the event sys_enter_open which is filtering by the filename argument. Looking at the format definition of it I can see there's a filename ...
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Kdump.service FAILED centOS 7

I am getting this error on my centos 7 x86_64 after "yum update". After rebooting the host it went into emergency mode. after entering this: systemctl status kdump.service I get this: ...
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4answers
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How does a Segmentation Fault work under-the-hood?

I can't seem to find any information on this aside from "the CPU's MMU sends a signal" and "the kernel directs it to the offending program, terminating it". I assumed that it probably sends the ...
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ASLR implementation details in Linux Kernel

I was able to easily locate code that ranzomizes "stack --> randomize_stack_top()" and "heap (brk) --> arch_randomize_brk()" in Linux kernel. However, I do not see the code which randomizes the ...
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73 views

get rid of “No Caching mode page found” message during boot

during early boot, I get following error message: [sdb] No Caching mode page found [sdb] Assuming drive cache: write through If I understand correctly, this is actually just a harmless info message ...
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How do I include the device tree with my kernel?

The purpose of the device tree is to "explain" the hardware to the kernel. But if the kernel is "customized" for certain hardware, how do I "insert" the device tree into the kernel at build time(so ...
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82 views

Linux exit function

I am trying to understand linux syscalls mechanism. I am reading a book and it in the book it says that exit function look like that(with gdb): mov $0x0,%ebx mov $0x1,%eax 80 int $0x80 I understand ...
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multithread access to platform device driver [migrated]

I am currently writing a platform device driver for embedded linux on ARM. What I've noticed is that a multithreaded application from user space can only access the driver one thread at a time, and ...
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1answer
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Managing Pre-Built Kernel Modules Across Kernel Versions

Please read the full question before attempting to answer, this is a bit oddball of a situation. I support a lot of server hardware test functionality, and essentially end up managing several ...
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how to merge device tree overlays to a single .dtb at build time?

My board boots via U-Boot and AFAIK that bootloader does not support device tree overlays, so I'm probably forced to generate a single, static .dtb will all relevant overlays (and settings??) already ...
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8 views

Copy a driver to other kernel?

I have installed RemixOS on my Laptop (sony vaio SVF 1521V1EB) but the Wifi is not working... However I could make it working on Ubuntu, so my question that am I able to copy the module files from the ...
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Q: How to tell the Linux Kernel to ignore MULTIPLE ata devices?

So, there were already questions about ignoring ata devices (like How to tell Linux Kernel > 3.0 to completely ignore a failing disk?) from where I got the info that one has to add something like ...
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1answer
46 views

Why does Linux have a maximum number of sound cards? [closed]

I'm specifically asking about CONFIG_SND_MAX_CARDS in the kernel. From the code using this config, for example in sound/usb/card.c for USB cards, soundcards are stored in plain arrays which are ...
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29 views

dd process real vs. sys time

I have two quad core workstations. One is based on Intel Atom x86_64 architecture (WS1). Another one is based on armv7l architecture (WS2). Both are running 3.10 kernel version. Identical busybox dd ...
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How do I support PTRACE_O_SUSPEND_SECCOMP and PR_SET_MM_MAP?

I'm trying to make Criu work. However, when I run sudo criu check, it gives me this error: prctl: PR_SET_MM_MAP is not supported, which is required for restoring user namespaces Error ...
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1answer
52 views

No space left to free up on rootfs partition to upgrade kernel

I want to upgrade Linux kernel from 3.16 to 4.3. Unfortunately when I run aptitude install linux-image-4.3.0-1-amd64 installation fails due to no space on rootfs partition. 117MB left, 174MB needed. ...
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How can I find the module responsible for interaction with keyboard [duplicate]

I have a laptop and want to be able to turn off keyboard for a while. I use this code: modprobe -r usbhid sleep 10 modprobe usbhid But as my keyboard is not usb, and it only blocks mouse. How can I ...
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1answer
62 views

Can a bootable NetBSD be built on OSX?

I've got OSX 10.9.5 . I want to build NetBSD (or at least it's kernel) on my OSX box. I've tried building the 'config' program but I can't find 'build.sh'. Is this possible and what would be the steps ...
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In Debian Jessie, make allnoconfig and make allyesconfig generate the same .config file

In debian jessie, I've installed the linux source with: sudo apt-get install linux-source I obtain a file /usr/src/linux-source-3.16.tar.xz, I copy it under my home directory, change the ownership ...
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31 views

Shared IRQs not operating properly

I'm having problems trying to make use of four out of six serial ports on my motherboard. The situation is: I have 6 serial ports available - ttyS0 to ttyS5 - of which 0 is a RS232 port on the edge ...
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23 views

What is the information present inside a kernel core dump

I am running CentOS 6. The system got a Kernel Panic and rebooted. I have enabled coredump generation, hence it generated a Kernel Core Dump of Size 300MB. What is the information that got ...
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1answer
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FreeBSD: How can I install kernel sources for 10.2-STABLE version?

Lots of articles and posts on internet tell how to install the kernel sources for FreeBSD x-RELEASE versions, but none of them for X-STABLE. For example, my FreeBSD version is 10.2-STABLE. How can ...
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Arch linux kernel upgrade from repositories

About two months ago I build a kernel (4.2.6-ARCH) from source according to this page, this is my current kernel version, the problem comes when I try to upgrade from the repositories, actually I did ...
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1answer
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Loading WiFi driver results in the whole system becoming unstable. How to debug?

I am not a linux kernel expert, but I got this new laptop and it's WiFi(RT3290LE) is not working. I tried solutions from various sources and they are not working. So it is upto me to solve it, and I ...
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CentOS update from 7.1 to 7.2 with 2.6 OpenVZ kernel?

We are using CentOS 7.1: $ cat /etc/redhat-release CentOS Linux release 7.1.1503 (Core) We deferred the 7.2 upgrade. It looks like it did not cause any problems so we are planning an upgrade. The ...
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prevent from writing to a large continuous section of virtual memory [closed]

How can an operating system kernel efficiently prevent a user process from writing to a large continuous section of virtual memory?
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Identifying disk drives during RHEL/CentOS/Fedora Installation

What steps are followed in order to identify a connected disk drive during Linux installation ? I am interested RHEL/CentOS/Fedora procedures. Is it entirely depends on the Kernel package and drivers ...
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108 views

Kernel panic after Gentoo install — cannot open root device

I have a Debian system on /dev/sda1 (/) and /dev/sda2 (extended, /dev/sda5 is /home, /dev/sda6 is swap). I want to install Gentoo in parallel, so I shrinked sda2 and created /dev/sda3, in which I ...
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Unable to setup TL-WN722N or Unable to install/complete headers

I would like to set up the tl-wn722b WLAN Adapter. I have a Kali Linux version for a Raspberry Pi. I tried to follow this tutorial: ...
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How does GUI works different from the shell CLI?

For example if I want to remove a file I would write rm command in my shell CLI. But when I delete a file using GUI how does the process works ? For shell it would find the filesystem for rm program ...
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95 views

“rcu_preempt detected stalls on CPUs / tasks” message appears to continue

My board continues to display the message below. The terminal does not have any input. What is it with the following message, which I know? (T, g, c, q ...) What is the cause of this phenomenon? ...
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255 views

Linux Kernel - Wacom Tablet (CTL-490DW-S) - Lockout

I'm a bit of a beginner with Linux and after trying to fix this over the last few days I've finally given up and need your help. I'm trying to use my new Wacom (CTL-490DW-S (Intuos DRAW)) drawing ...
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2answers
39 views

Copy the Linux kernel config file to another distribution

I am installing new Linux distro (gentoo) and I want to copy the linux kernel config I have here in the linux mint live USB to the Gentoo system. The way Mint has the kernel config file is ...
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Problem with xv6 on qemu

I was doing the assignment on this link --> http://zoo.cs.yale.edu/classes/cs422/2013/lec/l2-hw After running make qemu the assignment document says A separate window should appear ...
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1answer
43 views

change size of devtmpfs /dev/

My new kernel has CONFIG_DEVTMPFS enabled, and thus my /dev is mounted as devtmpfs. My old kernel was not using CONFIG_DEVTMPFS, and /dev used to be mounted as plain tmpfs. Now I have noticed, the ...
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1answer
71 views

cannot read key “net.ipv6.conf.all.stable_secret” in sysctl?

I am running kernel version as followings on an Arch Linux computer: [root@router ~ ]$ uname -a Linux router 4.2.5-1-ARCH #1 SMP PREEMPT Tue Oct 27 08:13:28 CET 2015 and I noticed that every time ...
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2answers
92 views

No /dev/mmcblk0 during boot

I am trying to install CentOS-6 on an eMMC drive. Since the supported 2.6.xx kernel from CentOS-6 doesn't support mmc, I compiled a newer kernel (4.2.6) which has updated mmc drivers. I tried booting ...
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Different Debian versions from two different commands

This might be silly, but I'm new to Linux. I wanted to check my current Debian version so I typed uname -a and it gave me some stuff including Debian 3.2.73. But Then I found this command cat ...
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How to enable auto upgrade of kernel-devel package when kernel version is upgraded?

I have a USB wireless adapter for which I need to re-install a kernel module every time the kernel gets upgraded to a new version. But for installing this kernel module again, I need to download and ...
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Error while building Linux kernel for versatile board

I'm trying to build the 2.6.32.69 version of Linux Kernel for versatile board but I got this error during the build step init/mounts.o: In function `tty_port_users': ...
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1answer
90 views

How the terminal can run programs and show its output? [closed]

I'm slowly creating a mental model of how linux works, and I've tried to simplify the most, my model of how linux works. Let's assume that the kernel boots and inits the only software it's gonna run: ...
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My SLES 11 uses 6 GB RAM while nothing is running. How can I find out what is needing it? [closed]

Can anybody tell me what is consuming that much memory on my SLES 11 SP3 server? I suspect a serious bug in the kernel that it does not release memory allocated by an application once it quits. This ...
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vmlinuz damaged

Hello everyone I am new here. I recently purchased Ubuntu 14.04 LTS DVD from a retailer store. Then I burned the iso into my pendrive and configured the file isolinux.cfg. The file was alright. ...