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

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What can interrupt execution of threads which are pinned to cores?

I do low-latency application development and I use isocpu and set thread affinity to reduce (eliminate?) context switching during my critical threads. However, I am unsure what other types of ...
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How does an OS detect an access to random memory address of a compiled program? [duplicate]

I've read a couple things about memory management/virtual memory and I need a little more details on one important point. If I compile a program and it does an access to a hard-coded address without ...
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43 views

uninstalled kernel cannot boot anymore

So, basically I messed up I tried updating debian wheezy to debian jessie and at some point aptitude wanted to uninstall the kernel, I got a warning but I had faith and allowed it. now I only have an ...
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111 views

Why are there module options AND driver options - e.g. for the i915 module?

The i915 Kernel module has several "module options" like the infamous enable_rc6. However, for the xorg config file, there are further options such as TearFree. I was wondering - why are there two ...
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kernel address and completly reserve memory block

I want to reserve initial 512M of total 1G RAM(768 MB is mapped as LOW MEM and 128 for vmalloc) The kernel data and text is residing in the initial section of RAM (starting at 0xc0008000). how it is ...
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57 views

Why the oldest kernel is marked as recommended in Linux Mint?

In update manager, there is View->"Linux kernels" option. It contains a list of kernels and as far as I know the freshest builds must be the most optimized and stable. For example in Linux Mint 17 ...
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linux kernel development, file open sys call [duplicate]

I just started reading OS books and traversing through linux kernel code. I was trying to locate how the file open system call is implemented. I found its declartion in /linux/fs.h. But I am not able ...
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192 views

How to install kernel development headers to staging with BuildRoot?

I am planning to do some Rasperry Pi C/C++ kernel module development using BuildRoot 2015.08.1. What works: I can build a kernel and a rootfs and boot the Raspberry Pi. I can build/rebuild a "hello ...
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USB behavior changes when laptop is plugged

I have a USB camera (from IDS) and I wanted to plug it to my new laptop. I installed the software and everything was fine until all frames dropped. After an long investigation I finally understood ...
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84 views

sysfs alternative to /proc/acpi/button/lid/LID/state

As you probably know ACPI procfs is deprecated in new kernel versions and with sysfs I don't know of a clean way of reading the state of the lid button. The only way I've come up with is hooking up ...
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Why are slab objects not reclaimed automatically

Everyday after a full system backup, various programs are failing with read errors until I run echo 2 > /proc/sys/vm/drop_caches to free reclaimable slab objects. For example, here's the output of ...
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63 views

Upgrade Squeeze to Wheezy now no modules.dep

After upgrading Squeeze to Wheezy my server will no longer boot. I'm only able to boot, by selecting a previous kernel (2.6.32). linux:~# find /lib/modules/3.2.0-4-amd64/ -maxdepth 2 /lib/modules/3.2....
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What is the minimal version of kernel on which ARM Slackware 14.0 will run?

I'm running Debian Lenny on a ARM NAS with 2.6.24 kernel. Debian in this version is missing many important security fixes and software patches, but when I've tried to run Debian Squeeze on the same ...
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32 views

Run script on startup for Old Linux kernel (3.0.0)

I need to run a script on system startup, but the Linux version is very old, so: There is no rc.local. Even when I created it and gave it a command, it was never run. There is no crontab at all. ...
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My RHELserver rebooting automatically I check the logs from boot logs

Server OS: uname -a Linux abc2.6.18-194.el5PAE #1 SMP Tue Mar 16 22:00:21 EDT 2010 i686 i686 i386 GNU/Linux # cat /etc/redhat-release Red Hat Enterprise Linux Server release 5.5 (Tikanga) [root@ABC~...
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262 views

Is there a way to temporarily disable segfault messages in dmesg?

Linux kernel keeps logging segfaults in ring buffer. a.out[25415]: segfault at 8049604 ip 08049604 sp bf88e3fc error 15 in a.out[8049000+1000] Is there a way to temporarily disable it? My usecase ...
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25 views

API for Kernel Module Development

I want to know if there is an API documentation listing all the functions/methods in the Header files? E.g. linux/kernel.h listing functions like printk(), linux/moduleparam.h indicating functions ...
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53 views

dd and USB - how does it work?

When you do: dd if=somefile of=/dev/sdX bs=1024 count =10 with a magnetic Hard Disk, and if the disk has say R/W multiple sector transfer: Max = 16 one can estimate that 16 * 512 = 8192 so setting a ...
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911 views

Why can't the kernel run init?

I've downloaded the Raspbian image on this page. I'm trying to compile a kernel that can be used to boot the image within qemu. I downloaded the Linux kernel source from kernel.org and ran: make ...
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16 views

Error in kernel recompilation

I have been trying to recompile the kernel in VirtualBox. But it resulted in an error make :*** [vmlinux] Error137. vmlinux is the name of my virtual machine. Printing kernel log gave [12560.424556] ...
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126 views

How to write a Patch for VyOS kernel

I am new to VyOS development. I have written a patch which will fetch info from the VyOS kernel module and write it on a netlink socket. But the problem is I am not sure if I should edit the kernel ...
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1answer
172 views

Centos 6.5 will not boot

The error below happens when booting up in to my distro of Centos 6.5. This happened after changing my paths in my fstab to UUID's. Server has two drives in RAID1 for the file system. I have access to ...
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461 views

How do I add CPU frequency governors to the Linux kernel?

CPU frequency scaling in Linux is by default performed via a governor, which as far as I know is included in the kernel. So far, on PC/server Linux kernels I've only seen the userspace, powersave, ...
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195 views

Linux/Embedded Linux - Understanding the Kernel and additional BSP specific components [closed]

*tldr; I would like to generally understand how the world of linux / embedded linux works. What do I need to do to take the Linux mainline and compile/deploy it on a board with different processors ...
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Microkernel (e.g. GNU Hurd) more secure than monolithic kernel (Linux)? [duplicate]

I would like to understand (in relatively layman's terms) if and how a microkernel such as the Mach-based GNU Hurd is more secure than a monolithic kernel such a Linux. Additionally, does a micro-...
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How can I benchmark or audit an embedded kernel?

Is there a reliable or industry standard way to benchmark or audit embedded kernel performance? The target of the audit is to determine the time that the kernel spends in certain critical section, ...
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86 views

Iptables: does dropping UDP packets take place in the user-space or kernel-space?

I know that Iptables is a user-space module, I also read it "configures" kernel modules to do big part of the filtering. So my question is, if I add a rule to allow only TCP:443 packets, would this be ...
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31 views

What's the code coverage of the Linux kernel when running a webserver in userspace?

I have a handful of Apache webservers serving up static files off disk. The files are too large to all fit in RAM. There's very little (if any) practical use to knowing this, but I'm wondering out of ...
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117 views

IPtables Test/Simulator/WhatIf/Dry run

I am currently debugging a rather strange network phenomenon and still believe my Linux netfilter firewall is the problem. These automagically generated rules and chains give me quite a headache and I ...
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Copying Driver Module files for manual install in another installation

Is it possible to extract the driver module files(including firmware files) from an installation(say i0) and place them manually in the same directory in another installation(say i1), and maybe edit ...
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1answer
36 views

porting kernel config to different architecture

I have a good Kernel .config setup for x86 that I'm happy with. Now I have a few different ARM-based devices (some without video output) that all come with their default pre-configured settings. I'd ...
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109 views

Hairpinning in linux

I have a router in which I installed a Linux system. I want my router supports NAT hairpinning Does a such feature exists in Kernel Linux? If yes how to activate it? Are there a patch to apply it on ...
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1answer
72 views

Is it safe to delete unused Linux kernels?

I don't want to use the 4.2.5-x kernel, I can't even boot with the proprietary Nvidia drivers. 3.16.7-24 kernel works fine. Is it safe to remove all 4.2.5-x kernels and how to do so? openSUSE 13.2
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Enumerate valid values for mknod

I have access to an embedded device which has a bunch of block/char files under /dev. However, this is not a satisfying description of the hardware, because since the firmware is shared with small ...
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1answer
27 views

udev rules official docs

I am looking official UDEV rules, documents, I have noticed there are changes in udev rules in RHEL 7. But could not find any documents some thing like 'request for changes'. Please help Thanks,
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How are GNU system utilities compatible with Linux?

According to GNU Hurd Architecture the GNU operating system was originally designed to be used with the GNU Hurd kernel which is a microkernel architecture. How is it that hobbyists were able to ...
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code generating /proc file system

In my assignment, I have added "casper" flag to task descriptor and it takes only 0, 1, 2 and 3 (default 0). I asked to "modify the code that generates the /proc filesystem so that its behavior is ...
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549 views

How can I get “RHEL 7.0 vmlinux” file?

I want to use crash on RHEL 7.0. Since crash needs vmlinux file, but I can't find it on /boot folder, only vmlinuxz: ...... vmlinuz-0-rescue-7c50639231494746b5dffc0a1ff84727 vmlinuz-3.10.0-123.el7....
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37 views

How do I store the data in disk directly in kernel module? [closed]

I capture the TCP packet in function of netif_receive_skb , I want to store the playload of TCP packet. we can't read/write the file in kernel module, so store in disk directly maybe a way? ...
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1answer
337 views

debian jessie backports wifi and bluetooth

I am running debian 8 and I need to update bluez and the debian kernel. Bluez needs to be above 5.23 to get a bluetooth with LE or smart bluetooth device to work. I am on a mac and I need to install ...
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Under what circumstances, if any, will the result of reading /proc/cpuinfo change?

What I understand so far is that when a program opens and reads any file under /proc/, the kernel will generate the information on the fly. In the specific case of cpuinfo most of that data is ...
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312 views

Installed libncurses5-dev, but can't make menuconfig! [closed]

I'm new to Linux, I found some links in Internet to Build and install Kernel(Just want to play :-P). I installed required libraries(ncurses libraries), kernel headers(sudo apt-get install linux-...
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Linux start_kernel - trap_init()

Some of these tasks that cpu_init() (which is called from trap_init) does I cannot really grasp: Call cpu_init() to do: 1 initialize per-CPU state 2 reload the GDT and IDT 3 mask off the eflags NT (...
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57 views

ALSA sounds card volume range numbers, and Difference between Control Names

I'm developing my first sound card driver in Ubuntu with ALSA. Implementing a volume control for the sound card I stumbled upon a few questions. 1) For the function that is assigned to ...
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165 views

Tuning Linux I/O Scheduler

I need a little help with properly tuning the Linux I/O Scheduler for spinning drives. I have a process that writes data to a huge (4-16TB) memory mapped file and is using SHED_FIFO. The kernel then ...
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What's the difference between ioremap and file operation mmap?

I'm currently working on a PCI device driver for Ubuntu. I have some example code about PCI driver, but I have difficult on understanding the ioremap and file_operation.mmap. The description of file ...
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40 views

file integrity between mount and mount point [closed]

Sub-tree rooted at /some_dir/B is mounted at /A/mount_point. If B contains foo.c, deleting /A/mount_point/foo.c will remove file from /some_dir/B/foo.c also. Is this correct? And what if I change only ...
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79 views

Pre-built Linux kernel with CONFIG_AEABI for Raspberry Pi emulation in qemu

I'm trying to run a RaspberryPi emulation on QEMU following the instructions from: http://cubik-tech.blogspot.com/2013/02/raspberry-pi-emulation-on-windows.html (and many similar posts) But I'm ...
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What challenges do people normally face using Arch Linux? [closed]

I'm setting up my Raspberry Pi 2 and deciding what linux distro to use. I'm leaning towards Raspbian and Arch Linux. Although Raspbian is definitely the safest option... Arch Linux seems like a more ...
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Does Linux still use rootfs?

In the kernel documentation file "ramfs, rootfs, and initramfs" it says Rootfs is a special instance of ramfs (or tmpfs, if that's enabled), which is always present in 2.6 systems. I have not ...