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

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Building example device driver error: insmod invalid module format

I am following the tutorial @ http://www.embeddedsystemonline.com/home/embedded-system/embedded_linux/lab3-linux-device-driver on step #7 of this tutorial, $ cd ...
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1answer
185 views

How do I determine the size of kernel block?

I need to find out what the kernel block size is from vmstat output. I am specifically looking for kernel block size as defined in Block devices and block sizes. There it says all Linux blocks are ...
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834 views

How to fix unreliable Realtek Wireless card on Ubuntu 13.04

I have a Realtek RTL8188CE wireless card and it works fine when I have a strong signal, but if I get even slightly away from the wifi I lose connectivity even though there is a strong Rx signal. I ...
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Updating a driver quirk in kernel

Os : Debian 6 Kernel Version : 2.6.32 I have been recently working with Linux application and now we have some little hard-disk issues where my motherboard doesn't support AHCI through bios. On ...
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sysrq-trigger doesn't accept parameter 'g'

I'm trying to debug the kernel. But I couldn't trigger kgdb with echo g > /proc/sysrq-trigger, it just prints help message. I have enabled kernel debugging, kgdb over serial, frame pointer etc. ...
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Human readable dmesg time stamps on OpenWRT

The output of dmesg shows the number of second+milliseconds since the system start. [ 10.470000] ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver [ 14.610000] device eth0 entered ...
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347 views

Would someone please explain lspci -vv output?

I have the following output from running lspci -vv -s 00:00 on my single board computer running Linux. 07:05.0 RAID bus controller: Adaptec AAC-RAID (Rocket) (rev 03) Subsystem: Adaptec ASR-2230S + ...
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792 views

Sign a module after kernel compilation

I've built a kernel in tmpfs, then I rebooted. Now I see a message when I compile the 3rd party module, NO SIGN [M] XXXX.ko How can I get it signed? The key pair generated during rpmbuild is lost ...
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yum installs kernel-devel different from my kernel version

I am attempting to install the VMWare player in Fedora 19. I am running into the problem that multiple users have had where VMware player cannot find the kernel headers. I have installed the ...
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Why is kworker consuming so many resources on Linux 3.0.0-12-server?

Last Friday I upgraded my Ubuntu server to 11.10, which now runs with a 3.0.0-12-server kernel. Since then the overall performance has dropped dramatically. Before the upgrade the system load was ...
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How many cores can Linux kernel handle?

I'm interested in theoretical limits, perhaps with examples of systems having huge numbers of CPU's.
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Change the root filesystem on an embedded system

I'm using Buildroot to generate an embedded Linux with a kernel v. 2.6.39, which in the end starts busybox. Everything works fine when building with Initramfs as "rootfs". But Initramfs isn't the best ...
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Cooking EDID and finding values for .S file

It became really annoying and the resolution is bad so I decided to make my EDID and pass that to the Kernel. (I am creating EDID for S20A300B and samsung says in its page the best RES for this ...
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59 views

Saving a kernel config file through menuconfig results with different options?

I'm experimenting with different kernel configuration files and wanted to keep a log on the ones I used. Here is the situation: There is configuration file called my_config which i want to use as ...
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3answers
93 views

None of the linux programs work except 'cd'

Before stating the question, here's what I did and observed before the problem started: On a fedora 18 Xfce, I tried compiling 3.6.10 kernel with a cdv driver, After many attempts, it finally ...
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How is an Interrupt handled in Linux?

I just know that Interrupt is a hardware signal assertion caused in a processor pin. But I would like to know how Linux OS handles it. What all are the things that happen when an interrupt occurs?
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What's the right way to set Linux kernel runtime parameters?

What's the prescribed way to set Linux kernel runtime parameters? I've seen sometimes that people will set these in files such as /etc/rc.local. Is this really the right way to do this?
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166 views

Permanently set kernel parameters [isolcpus] without grub?

Is there any way to set kernel parameters in an Ubuntu-based system without relying on grub? (not available in the target environment) Specifically I want to set the isolcpus parameter to dedicate ...
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Loading a kernel driver to a specific memory address

How can I load a kernel driver at a specific memory address? How could it be done with the following methods? commands/scripts like insmod or modprobe using C code (not sure if there may exist ...
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70 views

Linux and CPU usage

What does it mean for a core to run at different loads in different moments? How does a 10% load differ from a 90% load? How is this number calculated, essentially?
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43 views

File (products) of a kernel cross compilation

When the kernel is cross compiled (example. make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi-), what are the newly created files and their meanings? I'm not looking for a detailed explanation of each ...
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55 views

How can I compile minix when I make changes in libraries

I am looking for a way to compile minix. The make hdboot command seems to do nothing with the directories under /usr/src/lib. I changed only one .c file in syslib. Do I have to do make world for this ...
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45 views

Fedora 14 root missing capability

I am trying to run a process that performs a clone() operation using a set of flags (CLONE_NEWIPC, CLONE_NEWNET, ...) that require CAP_SYS_ADMIN capability. This should not be a problem since I am ...
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82 views

USB disk doesn't work on the new kernel

I just install the latest linux kernel (3.12.6) on my laptop(Lenovo). My system is Ubuntu 12.04. I just use the old configuration file in the old system which is "config-3.2.0-58-generic". Everything ...
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108 views

“unknown partition table” - misconfigured kernel

I was compiling a custom linux kernel for a newly installed machine, and after booting into the new kernel (3.12), the init process fails to find a root device, which I traced to the system getting an ...
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API with no system calls

The book 'Understanding Linux Kernel' says that 'for something abstract such as math functions, there may be no reason to make system calls'. Can any one please explain how is a system call not ...
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How to specify an ISO as the location of root filesystem for GRUB?

I'm trying to understand the Debian "booting from Hard Disk" installation manual. The process is as follows: I copy a kernel image, a ramdisk initrd and an ISO with installer to the hard drive and ...
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Microphones not working on Apple macbook Air 1,1 (Early 2008) under Linux

I'm running Linux on an mba. I can't make the microphones (neither external nor internal) work. I test using alsamixer and arecord -Dhw -fdat -vv mic.wav together with aplay -Dhw -vv mic.wav It ...
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274 views

Intentional kernel panic under Linux?

Is there any way to cause a kernel panic under Linux? I've heard of echo c > /proc/sysrq-trigger but it seems to just freeze, and I'm not sure it's a kernel panic. Is there any C program I can ...
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What software allows the change of runtime-environment, while keeping the same kernel running?

I know that with a GNU/Linux distribution you can switch between different distributions at runtime when they use the same kernel or the kernel is compatible between 2 or more different distributions; ...
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Installing OpenVPN to replace Cisco VPN because Cisco will not work with the kernel I am on or downgrade instead?

I had difficulties installing Cisco5.0 VPN on my Ubuntu 10.04 LTS. I asked for assistance in this question: link to previous question. The answer is that this Cisco program will run on only older ...
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Is it possible for grub2 to detect some specific CPU features and choose a proper kernel to boot?

I want to configure grub to check some CPU features on startup and choose a proper kernel to boot (e.g. multiple cores -> kernel with SMP support). Is it possible? If so, then how do I do it?
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How to disable USB autosuspend on kernel 3.7.10 or above?

I've updated my HTPC from kernel 3.7.10 to 3.10.7 and it seems CONFIG_USB_SUSPEND is now gone from the kernel options and included in PM. The main problem I'm facing is that I have an external HDD ...
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Location of the kernel binary (when not in /boot)?

I failed to find the kernel binary in the standard location in /boot. I've also searched the whole file system for vmlinux or bzimage find / -iname vmlin* find / -iname bzimage However, this is an ...
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133 views

GRUB2 Insert additional kernel modules

GRUB2 doesn't have the menu.lst file. How do I configure a boot script. During boot, I hit E on the kernel image that I want to modify and make my modifications. But I would prefer to make the ...
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7answers
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Understanding the Linux kernel source

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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How to blacklist a correct bad RAM sector according to MemTest86+ error indication?

MemTest86+ (the version included with Ubuntu 13.04) says Failing address: 002f796c48 - 759.5 MB What should I specify in the memmap kernel parameter to bypass this area? I've tried running ...
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94 views

Upgrade kernel for linux system without upgrading user apps/libs?

I built a custom Linux "recovery-cd" image that consists of a compressed initrd and boots via bcdedit (like Ubuntu Wubi) instead of a physical CD. It has various recovery tools for partition editing, ...
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333 views

What would I get when sudo a kernel-destructive program?

It suddenly comes to me how easy it will be for a sudoer to crash the kernel, so I tried something like this: #include<stdio.h> int main(){ printf("hello world"); int a; ...
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103 views

What is the maximum allowed number of TTY, is it defined anywhere in kernel headers?

What's the maximum allowed number of TTYs? I found pty.max, but is there anything similar for TTYs? Or is it defined as a fixed value in kernel headers, I couldn't find that
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2answers
103 views

How to fake a filesystem that cannot be mounted by others

I'm currently working on a project. There's an Ubuntu Linux system installed on a disk, DA, mounting the other disk, DB. What it requires is that DB can be only mounted by DA in order to prevent data ...
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90 views

How can I run gdb in one machine and run kgdb kernel in another machine?

I want to run two machine: debugged machine: compiled kernel with kgdb option. debugger machine: for running gdb How can I debug machine 1 from machine 2?
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Change the number of generated /dev/tty devices

I'm building an embedded Linux system, based on Gentoo. Using udev, all tty devices are probed with a PROGRAM stanza to determine if they are a modem. Right now the system boots up with 64 /dev/tty*. ...
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HDD indicator blinks when I run out of memory, but I have no swap configured [duplicate]

I'm running Arch Linux, with 8 GB memory and no swap defined. Sometimes it ran out of memory, then my system get a little bit stuck, and I can see the HDD indicator blinking. Then I restart X, which ...
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4answers
134 views

Is it necessary to reboot after a kernel upgrade (via APT)?

I have been wondering this for quite a while. Let's say that you have a Debian server that you keep updated via APT. Usually (every 1-2 months) there are some kernel updates, which will update the ...
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Qemu: No file system could mount root (unable to mount roofs)

In Linux, I've created the root file system (rootfs) by following commands: dd if=/dev/zero of=ramdisk.img bs=1M count=4 mkfs.ext2 ramdisk.img sudo mount -o loop ramdisk.img rootfs sudo cp init ...
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Kernel IPsec SA database: FIFO instead of LIFO

When processing an IP packet, the kernel looks into the security policy (SP) database to determine whether it is to be protected with IPsec. If the identifiers of the packet (e.g. IP addresses, etc.) ...
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Linux signals logger

I'm looking for a signals logger for the Linux kernel, without patching of kernel. I found many articles with patching, but I am not interested in that. I'm running default Ubuntu 13.04. # uname -a ...
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2k views

How can I write to dmesg from command line?

I'd like to write a statement to dmesg. [How] can I do this?
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938 views

What's the difference between a kernel oops and a kernel panic?

I know what a kernel panic is, but I've also seen the term "kernel oops". I'd always thought they were the same, but maybe not. So: What is a kernel oops, and how is it different from a kernel panic? ...