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

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Centos 7 boot up with custom kernel problem

I have installed centos 7 on virtualbox machine which has kernel-3.10.0-123.20.1.el7.x86_64. I am trying to build Linux kernel from kernel sources. I downloaded the kernel source files from: ...
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197 views

dmesg: pci BAR 7: can't assign io

I have VMware virtual machine running Debian Wheezy. I have compiled my own kernel 3.14. I have noticed dmesg is flooded with messages pci BAR 7: can't assign io (size 0x1000). I have no idea what ...
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271 views

EDID Invalid on USB DisplayLink Device

I have a Sabrent USB to HDMI adapter which is a DisplayLink device. It's recognized by udl as being a DisplayLink device, yet seems to be rejected/disabled due to having an invalid EDID: ...
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2k views

“Northbridge Error (node 0): ECC Error in the Probe Filter directory”

I've received an e-mail from a user worried that the following errors on one of his servers is indicative of a serious problem. The trouble is, the errors below are all that I have to go on. I ...
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132 views

update kernel without restart

Recently Linux got a new feature called Live Kernel Patching, which you means you dont have to restart your system to update kernel. Is there any other kernel which has this feature already or Linux ...
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109 views

How to prevent kernel or any broadcast messages from flooding the TTYs?

Because of some hot-plugging issue, similar to what talked of here, the TTY displays show a continuous stream of messages (which are also logged in the /var/log directory). Every text I key in flows ...
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193 views

Why does a device show up as hidraw instead of hiddev?

I read the kernel documentation for hidraw and hiddev, and I understand the differences, but I am wondering how the kernel decides whether or not a device should show up as /dev/hidraw* or ...
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761 views

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 ...
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144 views

Why are block sizes limited by page size in Linux?

In many (all?) file systems that Linux uses, including ext2/3/4, the maximum block size is the page size of the architecture Linux is running on, ie. 4KiB on x86. Why is there this limit? Might this ...
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244 views

How to set CONFIG_PREEMPT_NONE in RHEL 6.4 (linux)

I am trying to tune the RHEL6.4 Kernel to handle server style load for of my application. With RHEL 6 scheduler has been changed to CFS and with RHEL 5 my application works fine. I would like change ...
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281 views

My SMDK2416 (for s3c2416) kernel works on 64MRAM but crashed on 128M

I'm currently working on embedded arm linux with smdk2416(s3c2416) The kernel is working on the 64MRAM. Recently, I need to increase the RAM from 64M to 128MB with 64MB on bank0 and 64MB on bank1. ...
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696 views

How extended (4MB) and regular (4KB) paging coexist?

On x86 architecture, "Extended paging" allows page frames (physical memory) to be 4 MB instead of 4 KB. The book "Understanding the Linux Kernel, 3rd" at chapter 2 "Memory Addressing", sub-chapter ...
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265 views

When would I use FBDEV vs DRM vs DSS?

I'm new to Linux graphics, and I'm interested in developing a graphics driver. I see that Linux supports three methods for writing graphics to the display device FBDEV DRM DSS2 When would I use ...
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275 views

Can I make the boot even more verbose than loglevel=7 using kernel parameters?

I have an error when booting on a machine, my machine is stuck with the error message: Booting a command list. I can see this message when I add loglevel=7to the kernel parameters via grub boot ...
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45 views

How to insert a modified ELF loader given the current ELF loader is present?

I need to modify the ELF loader's kernel implementation of an Ubuntu 14.04 distribution. Having downloaded the sources using: sudo apt-get source linux-image-$(uname -r) I ran the configuration ...
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36 views

Is there support for flattened device tree in Sparc 32 port of the Linux kernel?

We are trying to write a minimal bootloader for booting the linux kernel on a Sparc V8 processor simulator. From what I understand, the interface between the bootloader and kernel consists of a data ...
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81 views

“can't write to batman adv kernel file” while using “batctl p mac-address”

I installed batman-adv and batctl on Ubuntu 14.04.1. When I issue the comand: batctl p 00:16:bf:01:68:46 I get this error: Error - can't write to batman adv kernel file ...
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115 views

What is the minimum round robin scheduing interval supported by Linux?

For some reason, I want to have 10 processes share the same CPU core by affinity. As you know, to achieve CPU sharing between processes, we can exploit the Linux round robin (RR) scheduling policy. ...
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38 views

Possibile sources of 5us-20us latency gap when sending long block of of serial data to tty device?

I have a trivial C program that just sends a large block of data out the serial port at a fast baud rate. When looking at the bits actually coming out of the port, I see that there is a almost always ...
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58 views

Is a page with “PROT_NONE bit set” eligible for swapping?

From the following link: Page Table Management - kernel.org, I understood that the bits PROT_NONE and PRESENT can be used to let the OS know that a page is protected but is resident in memory. I am ...
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104 views

How does the kernel store the virtual memory area?

I am trying to understand do_page_fault in fault.c (x86 architecture). I came across the method access_error where we compare the error code to the vm flags. As per my understanding, we are checking ...
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161 views

Virtual kernel memory layout in dmesg linux kernel 2.6.31

I'm working on a embedded linux project for ARM architecture, kernel version is 2.6.31.12-rt21. In dmesg, I cannot see the virtual kernel memory layout like this: virtual kernel memory layout: ...
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362 views

Server won't boot, kernel panic - not syncing

After a reboot of a CentOS 6.2 server we are getting a kernel panic with the following error: Kernel panic - not syncing: Attempted to kill init! Panic occurred, switching back to text console ...
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151 views

kdump doesn't produce core dump after buggy module is loaded

I am running kernel 3.14.4 on Fedora 18. I am experimenting with a kernel module I am making. The module has a bug (at least one) and crashes the kernel. Sometimes I see a stack trace on my frozen ...
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180 views

How to interpret cpu_idle and cpu_frequency event's trace logged by ftrace?

I used ftrace to trace two events, cpu_frequency and cpu_idle. I am not able to find out any documentation which states how to interpret this information. I have provided two snippets from the ...
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287 views

Some questions compiling linux kernel with make-kpkg

I'm doing my first steps compiling the linux kernel and adding a new system call. I've managed to do it, but I still have some questions. For this task, I has set up a Virtual Machine guesting debian ...
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89 views

Why does the kernel boot faster with less memory allocated?

This is not a important question, I'm just curious. Something strange happened, which isn't quiet clear to me: In the kernel command line, the amount of the memory can be set statically with the ...
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67 views

Detach keyboard from the kernel

I am writing a remote controller app for an octocopter and want to use a keyboard as an input device for this app but I don't want it to have any effect outside this app. Somehow I would like to make ...
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156 views

How can I automatically include all firmware needed by selected Linux kernel modules

I have certain modules which I need compiled into the kernel. Some of these modules require firmware, which used to be automatically included from /usr/src/linux/firmware/. However, no new firmware ...
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63 views

Linux kernel API changes/additions

I'm trying to find a webpage or docs or XYZ that will allow me to see all the API changes/additions/removals between two kernel versions. I found http://kernelnewbies.org/LinuxChanges, but I'm not ...
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328 views

how to stop kernel threads preempting real time user space processes?

I created some processes in user space and tried to visualize its working in kernelshark with the trace recorded using trace-cmd. But kernel processes like the ones shown below are preempting my ...
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529 views

PC sudden shutdown, Sensors show normal temps, Thermal event interrupts shows 1276

I'm experiencing sudden shutdowns on my Linux systems. Using Ubuntu 12.04, my kernel version is 3.5.0-37-generic #58~precise1-Ubuntu. Running a Acer M5 581t(G) with 6 gigs ram laptop. I have been ...
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179 views

What changed between kernels 3.7 and 3.9 that affects LVM/RAID root file systems?

I'm trying to fix a (very messy) system that the user hosed by running a kernel upgrade from 3.7.10 to 3.9.6. the root file system is on an LVM volume on top of a software RAID array. The boot manager ...
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887 views

Unable to install the selected kernel

I have problem with my DVD drive. It's corrupted and when I'm trying to install Ubuntu it stucks (even with the miniISO) I was able to successfully start the OS from system rescue CD. I'd like to ...
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265 views

Update jiffies value after waking up from suspend

The global variable jiffies holds the number of ticks that have occurred since the system booted. On boot, the kernel initializes the variable to zero, and it is incremented by one during each timer ...
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60 views

kgdb not returning control to gdb

I've compiled a kernel with kgdb support and I'm trying to debug it. I have two machines running, a debug machine (running the kgdb kernel) and the machine I'm using to debug it. They are connected ...
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3k views

mounting udev on /dev failed: No such device

I am trying to compile Linux kernel 3.2.36 with its source code on the x86_64 architecture. I followed the following set of commands under my Linux source distribution directory: make defconfig ...
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1k views

CFLAGS in Linux kernel makefiles: which one is used when?

I'm not familiar with Makefiles, I can kinda understand them, but with the Linux Kernel I have a question. (Using 3.7.1, Patched with BFS so line numbers may be a bit off) On line 248 HOSTCFLAGS ...
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408 views

Error cross compiling linux kernel using buildroot

I am trying to build a kernel bt in cross compiling the kernel when I ran following command make CROSS_COMPILE=i686-linux- ARCH=x86 I got the following error: UCLIB_EXTRA_CFLAGS="" \ ...
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102 views

How to deal with closed source modules when configuring a new kernel build

I found this command very useful: make localmodconfig However, having some closed source drivers/modules ends up being a problem because this command can't find an appropriate way of including the ...
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398 views

Kernel 3.0.0-1 and NVIDIA driver boot problems

I can't boot kernel 3.0.0-1 on Asus G53S running Debian, it freezes when booting with: NVRM loading NVIDIA Unix x86_64 kernel module 275.28 then it times out with: udevd[350]: timeout: killing ...
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11 views

how to set or know scaling driver in linux kernel

I am trying to modify the scheduler/governor. For the same I need to know what CPUFreq Driver or scalling driver am I configured to run. 1.Where can I find what scaling driver am I configured to ...
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32 views

How to set SyslogIdentifier in [SERVICE] section of systemd service file as empty?

I want to set SyslogIdentifier in [SERVICE] section of systemd service file as empty, so that nothing is prefixed in the logs. I tried below options: 1) Mentioning nothing: SyslogIdentifier= ...
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126 views

How to rotate the LCD screen/framebuffer to 180 degree?

I have a custom board with a Freecale i.MX6Q SoC. I am using Linux kernel 3.03.35 and LCD is 3.5 inch RGB type display. I want to rotate my LCD screen to 180 degree. I tried a lot to pass parameters ...
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12 views

dracut md5sum boot directory

This has been going on for a few months now, but my initramfs (and kernel) for that matter have been placed in /boot/{some hash}/{kernel version}/{initramfs,linux}. Did dracut or some other module ...
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13 views

Constant 60KB Shared library memory on /proc/<pid>/maps

In a quest for understanding RAM requirements of system processes, I arrived to analysis of /proc/pid/maps. I have noticed a pattern: many shared libraries have exactly 60KB space allocated in their ...
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133 views

Can a zImage be used with U-Boot and ArchLinuxARM?

I am using U-Boot on a Cubieboard 2, sun7i AllWinner A20 board to boot into ArchLinux ARM. The kernel version that I have is the sun7i latest, which is 3.4.103-5-ARCH so, in kernel terms, it's a bit ...
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57 views

Looking for a Distro for a beginner in kernel hacking

I'm currently trying to learn the basics of the linux kernel via Linux Kernel in a Nutshell and Linux Kernel Development books, the problem is that when using Ubuntu, there are a lot redundant ...
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44 views

Meaning of an ampersand prefix in a device tree

I am looking at a DTS file which tries to specify different nodes, but interestingly I find a few nodes having different style of nomenclature. / { model = "TI AM335x BeagleBone Black"; ...
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23 views

Investigating Active MemInfo

I am seeing high Active usage when I do a cat /proc/meminfo : MemTotal: 65965328 kB MemFree: 51640992 kB Buffers: 1050332 kB Cached: 8516112 kB SwapCached: 0 kB Active: 11512732 kB Inactive: 1878028 ...