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

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real time kernel / low latency comes from the vanilla source

Does the vanilla source provide real time / low latency functionality ?
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NTPD Nanokernel

I had a couple of questions about the NTP Nanokernel as explained here: http://www.eecis.udel.edu/~mills/database/brief/nano/nano.pdf The big question is how does this Nanokernel manage to deliver an ...
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25 views

module prints to kernel log with delay

I've created a basic linux kernel module, which does the following: static __init int init(void) { printk(KERN_DEBUG "Banana"); return 0; } And of course: module_init(init); Strangely, I ...
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1answer
82 views

Does each network packet cause an interrupt to CPU?

While I know that lot of packet processing(CRC calculations, packet segmentation handling, etc) can be offloaded to NIC, then does each packet still cause an interrupt to CPU? Is there a difference if ...
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1answer
144 views

Questions about behaviour of running LiveCD Linux after unmounting a CD-ROM

Could anyone explain what happens in system after unplugging CD-ROM during working with LiveCD session? Suppose that I'm using Ubuntu LiveCD and suddenly by accident the CD-ROM disconnect for a ...
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1answer
1k views

How to Find and reload specific driver from kernel?

I am using Crunchbang 64 bit O.S. with a ASUS N150 wireless adapter. Everytime I close my laptop and it enters sleep mode, when I "wake it up" I am unable to connect back using the wireless adapter, I ...
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1answer
60 views

Changing linux config from 32 bit to 64 bit loses RTC

I have a config from a 32-bit linux 3.12.18, and was trying to compile a 64 bit version with most settings like selected drivers etc. the same as in 32 bit version. For this I used make menuconfig ...
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61 views

latest arch linux on beaglebone black

I have installed arch linux using what I assumed was the latest kernel at http://archlinuxarm.org/os/ArchLinuxARM-am33x-latest.tar.gz But this only installs 3.8.13 and I understand that there are ...
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64 views

Changing CPU frequency programmatically

I have seen that standard CPU Frequency driver(comes with default package with linux kernel) can change the CPU frequency at runtime, when being used under the supervision of "Ondemand" governor. ...
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2k views

Turning off power to usb port. Or turn off power to entire usb subsystem

I have a usb lamp which I specifically bought in order to turn it off programmatically at a certain time, thus I need to remove the power to its usb port. I believe I have a usb-hub at usb6. The lamp ...
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452 views

FreeBSD boot problem, UEFI or LEGACY and GPT disk

i have a computer based on GPT disks with triple boot. For the moment i have two OSes working on my computer (OSX and Windows). I want to make a FreeBSD installation, he work perfectly when i boot on ...
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memory limit of the Linux kernel

I have a perplexing problem. I have a library which uses sg for executing customized CDBs. There are a couple of systems which routinely have issues with memory allocation in sg. Usually, the sg ...
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Does Linux log when a process is started, and the PID that gets assigned to it? Where can I find that log?

When my Ubuntu server starts up, I see a message that says: kernel: [11.895392] init: failsafe main process (631) killed by TERM signal. I would like to know what process this is but I'm not sure ...
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1answer
176 views

Calls to sync/fsync slow down after 30 minutes uptime

After 30 minutes of uptime using Ubuntu 14.04 with a hybrid SSD I see many processes blocking IO using iotop. This is during disk writes, for example if I open and close an empty file in gedit it can ...
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1answer
271 views

Kernel 3.14 not working with ATIProprietary fglrx?

On my debian laptop I installed kernel 3.14 so I have the alx driver so my ethernet works, I originally had the 3.2 kernel (Debian 7.7). AFter installing the new kernel, gnome3 went back to the ...
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1answer
68 views

Walk-through into make (menu)config's options [closed]

I need to customize the kernel a lot for a custom system. Most of my changes concern the kernel's memory usage (something like an embedded kernel). There are a lot of things enabled by default in the ...
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2answers
571 views

Why CONFIG_NO_HZ is not set by default

In the Linux Kernel CONFIG_NO_HZ is not set. But an initial reading suggests that setting that option would be nice from a performance point of view. But reading some posts like this made me think ...
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How to suppress input overrun messages

I have a Raspberry Pi running Raspbian (a Debian flavor: Linux version 3.12-1-rpi (debian-kernel@lists.debian.org) (gcc version 4.7.2 (Debian 4.7.2-5+rpi1) ) #1 Debian 3.12.9-1+rpi1 (2014-05-19) ). ...
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233 views

IPTABLES comment: No chain/target/match by that name

Faced with error when adding new rule with 'comment': # iptables -I INPUT 1 --source 66.***.***.78 -j REJECT -m comment --comment "Some" iptables: No chain/target/match by that name. Without ...
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1answer
185 views

Full UEFI System, Grub 2 self-compiled + Clover 2, Debian kFreeBSD installation?

I've a computer with full installation UEFI system, with 2 bootloaders (GRUB & Clover on ESP) clover is the primary bootloader that allows me to load OSX and grub2. I want to make a new install of ...
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36 views

open() sys call [closed]

Process A wants to open a file fd1 = open("/var/file1", O_RDONLY); In the process of opening file1 which table is referred first system wide file table or file descriptor table or in-core inode ...
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How can I compile and run a program designed for an older kernel version (2.6) in a newer kernel (3.16)?

I'm trying to run a driver for a network card, but it only supports kernels up to 2.6.32. I need to be able to use this piece of hardware to connect to the Internet. The device I'm using is "VIA ...
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3answers
64 views

Linux Distro name API to get name of linux distro in a driver code?

I am writing a common code in a driver to get the distros name and host name. host name i am taking from struct utsname{nodename[]}, but how do I get the distro name?
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Who wrote the “Linux kernel” (Linus Torvalds and his team)?

Who are the authors of the pure Linux kernel from scratch, which was integrated with GNU tools and formed the full GNU/Linux Operating system in the 1990s? I have read some wiki articles but I haven't ...
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Which function in Linux kernel do the powering off action?

I am not asking how to shut down. I am asking how to cut of the power. What is the function in Linux kernel code do the action of cutting of the power? And please explain the code.
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30 views

What directory houses the scripts that get executed with new kernel installations?

This one is pretty much a straightfoward question/answer I just can't locate the information. I'm trying to automate the re-installation of VMWare tools based off when a new kernel is installed. I ...
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RHEL 6.5 erroneously marking Fusion-io RAID1 card as failed

I am getting the following error every hour for a Fusion-io ioscale2 RAID1 (mirror) configuration. However, the logical volume is mounted and accessible. I do not see similar error in the ...
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1answer
68 views

How can I boot into Ubuntu with a linux kernel with an earlier version?

Part of the output of ls -ld /usr/src/linux-headers* on ubuntu 12.04 is: drwxr-xr-x 24 root root 4096 Jun 4 2013 /usr/src/linux-headers-3.2.0-45 drwxr-xr-x 7 root root 4096 Jun 4 2013 ...
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1answer
132 views

yum update returns kernel error

I want to install virtualbox in fedora20. I have followed the instruction here: http://www.if-not-true-then-false.com/2010/install-virtualbox-with-yum-on-fedora-centos-red-hat-rhel/ but when I ...
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How/where are linux device capabilities / bitfields set?

I have a device that has this output in /proc/bus/input/devices: I: Bus=0003 Vendor=05b8 Product=3280 Version=0111 N: Name="PixArt USB Optical Mouse" P: Phys=usb-0000:00:1a.0-1.1/input0 S: ...
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How to force Linux kernel to “freeze” (or nearly freeze) for a few hundred milliseconds

We are running a real-time process on a non real-time kernel (CentOS 6), and this is probably not going to change. We have a streaming video application that requires about 500 MB/s of PCIe traffic ...
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How do I set kernel-ml default in CentOS?

I have installed kernel-ml package from http://elrepo.org/tiki/kernel-ml Now I have both the original CentOS kernel and kernel-ml. How do I set kernel-ml as default on boot? Thank you!
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68 views

How can I check if a certain patch is already installed in my system?

I am about to install a patch for wireless drivers named Compat Wireless in order to solve a problem with my WiFi channel (it locks on the not existing -1 channel) on my Ubuntu Linux v12.04 and Kali ...
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Surface Pro Compatible Wireless cards and drivers

In reference to this post: Surface Pro Wifi Issues on Mint KDE 17 there doesn't seem to be any solution to fixing the wifi issues on the Surface Pro when running Linux. The Marvell card doesn't even ...
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1answer
190 views

Which Debian kernel should I install?

I've started installing Debian testing on amd64 and I've come to a screen asking me to install a kernel. It gives me a choice between linux-image-3.16-2-amd64, linux-image-amd64, and none. What is ...
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1answer
1k views

Linux-image-3.2.0.4-amd64 vs linux-image-amd64 [duplicate]

Installing Debian I have to choose between the kernels linux-image-3.2.0.4-amd64 linux-image-amd64 What's the difference?
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1answer
1k views

libusb_init() returns -99

I have successfully built both libfreenect (driver for Xbox Kinect) and libusb (which is a dependency). However, if I try to open the Kinect using the freenect_init(...) function, it returns -99. I ...
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1answer
197 views

How to change the kernel max PID number? [duplicate]

The default PID max number is 32768. To get this information type: cat /proc/sys/kernel/pid_max 32768 or sysctl kernel.pid_max kernel.pid_max = 32768 Now, I want to change this number... but I ...
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kernel log in /var/log/messages: task xxx blocked blocked for more than 120 seconds . System frozen [closed]

Monit sent out emails in the morning that my java app on the server was not responding to HTTP calls made on the 127.0.0.1 interface. App log shows nothing out of the ordinary, nginx log shows no ...
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4answers
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Determining cause of Linux kernel panic

I'm running an Ubuntu 12.04 derivative (amd64) and I've been having really strange issues recently. Out of the blue, seemingly, X will freeze completely for a while (1-3 minutes?) and then the system ...
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1answer
130 views

Linux kernel 3.10.0-123.4.2 processes [flush] aren't present

I am using CentOS 7 with "3.10.0-123.4.2.el7.x86_64" version, but I don't know why the kernel threads named flush aren't present in this kernel version. I tried to look in the kernel change log, but ...
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1answer
5k views

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 ...
0
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1answer
144 views

Role of the Intel P state driver

I searched high and low for what “Intel P state” is and what it does. I found out that it has to do with performance and power consumption. I learned that if you build it in the kernel, it'll becomes ...
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148 views

How to display printk messages filtered by level as they come?

I wrote a hello word module that performs a printk when it is loaded in level ALERT and another printk when it is released with level INFO: #include <linux/module.h> #include ...
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813 views

Kernel 3.14.1 compilation errors

I installed the kernel 3.14.1 and there seem to be no issues. uname -r 3.14.1-031401-generic However, when I try to go to the folder and try to do a make it fails. I see that multiple files are ...
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56 views

Best approach to adding a kernel driver

I have a task to complete. An LED must be controlled immediately after the kernel loads and into the launch of a Debian system. It also must be controlled in user land. I already have basic LED ...
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1answer
89 views

What does kernel-wedge do?

After looking at the package description and using kernel-wedge help, I'm not really sure what it does. Does it take a .deb kernel package and split it into smaller packages? Does it compile a ...
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How to recompile official OpenSUSE kernel & initrd?

But it is not okay. I want all of the suse patches applied, I want an official initrd to be generated, and I want to make rpms from all of them. So, I want to recompile the kernel just as the SuSE ...
0
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1answer
157 views

Mount JFFS2 FS in openwrt

I'm trying to mount 1[MB] of flash as JFFS2 FS in openwrt environment, using 128[MB] NAND flash (4 bit ECC). I'm using the following sequence - flash_eraseall -j dev/mtd6 mount -t jffs2 -o noatime ...
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Explanation of the building process of the kernel on Ubuntu/Debian systems

I'm getting into Linux kernel programming and I have successfully built my own kernel several times now. However, I have done it using step by step guides found from the internet and I don't really ...