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

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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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55 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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29 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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46 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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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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61 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
51 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 ...
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26 views

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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23 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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39 views

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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40 views

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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163 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 ...
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1answer
29 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
211 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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134 views

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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117 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 ...
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11 views

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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1answer
36 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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1answer
83 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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1answer
543 views

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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39 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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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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27 views

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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34 views

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 ...
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Driver Module Backup from a Running Installation

Is it theoretically possible to make a backup of all the driver modules (especially the ones that are not merged into the original kernel) from a running installation of LinuxMint? The source of the ...
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84 views

How to understand the modinfo output?

I'm just trying to understand the modinfo output that describes a kernel module. For instance, in the case of the module i915, the output looks like this: $ modinfo i915 filename: ...
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USB device keeps disconnecting on boot

When booting a linux kernel off a usb device, via a usb hub, a light panel attached to my board (via the hub) disconnects during the kernel boot. Once the system is booted I unplug the panel and ...
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33 views

how to enable 1MB dma-kmalloc

I'm running a ubuntu 15.10 VM and testing code that will allocate 1MB dma buffers. However, from the /proc/slabinfo, the max that can be allocated is 8K dma-kmalloc-8192 0 0 8192 4 ...
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51 views

uncompression error, no file system could mount root, kernel panic not syncing

I am using Linux Mint maya on vbox (Windows XP host), it's working fine without issues. Now I would like to install it with XP(dual boot) so I made a bootable DVD with same iso which I used for vbox, ...
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What's the use of this empty function declaration in exec.c kernel source?

I see some empty functions in the Linux kernel file exec.c here: http://lxr.free-electrons.com/source/fs/exec.c#L235 But, some functions like free_arg_pages is again declared below here (with same ...
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There is possible to read 1-wire (ds18b20) without waiting for conversion?

I want to read temperature value from ds18b20 by 1-wire interface without blocking. There is any way to do that? I tried fnctl(fd, F_SETFL, O_NONBLOCK) but its not working. Actually I have a loop ...
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25 views

Backlight control configuration misbehaves on an Ideapad.

I did a clean Ubuntu install on a Lenovo Ideapad P500. The backlight started okay, but after pressing the keyboard light function once, it got reset to a very dark state. The brightness setting ...
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105 views

Two compiles of the same kernel version: one boots, one unable to find root device

I have two compiles of the same kernel version (4.0.5+gentoo patches). One boots, correctly, but lacks several kernel CONFIG flags. Adding those flags and running make all && make install ...
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Negative dentry

When we do rm foo.bar, kernel decrements inode ref count and checks if it's become zero. In case of 0, inode is removed and foo.bar dentry becomes negative. This negative dentry continues to stay in ...
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What hardware support is needed for linux to do `gettimeofday` / `clock_gettime` in userspace using `hped`?

On reasonably modern systems Linux can service "system" calls like gettimeofday and clock_gettime entirely in userspace through the linux-vdso.so (or linux-gate.so) virtual library, so it does not ...
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685 views

Kernel panic : Kernel offset disabled

I was trying to install the linux-next kernel in my system with the following steps. Copied the existing configuration file from /boot to the root of source directory Updated the .config file with ...
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Disk benchmark IO depth clear out

When I'm manipulating over some benchmark tool I/O depth, what exactly am I changing? Let's say I have SATA disk on /dev/sda. If I run hdparm: root@linaro-gnome:~# hdparm -I /dev/sda | grep Queue ...
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what do I need to activate in my kernel to get dm-crypt

I am on an armv7, kernel 3.15.0 I have enabled device mapper and crypt target support. but I cannot find anything that specifically references dm-crypt in my kernel menu, would someone please be able ...
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1answer
131 views

Which distro uses a Kernel 3.19 or above

I am looking for a distro that supports Intel HD 6000 , i believe kernel 3.19 and above is needed. So does anyone know of a beginner friendly distro Many thanks
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2answers
66 views

ACPI wakeup 4-letters code meaning?

I have to disable some event to avoid an immediate wakeup after suspend in my desktop machine, and I made it by trial and error (works well, so that is not a problem). But I wonder... for example in ...
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140 views

Errors cross-compiling with distcc

I'm currently attempting a build of the Raspbian kernel using both a cross-compiler (for the Raspberry Pi 2's ARM processor) and distcc, based on the instructions posted at the Raspberry Pi website. I ...
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1answer
188 views

What is the usual Allocation unit for a process on Linux?

I'm currently studying memory management in Operating Systems. Allocation Unit is the smallest unit of memory the OS will give to any process. I've read in this page, in the 'Memory allocation ...
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1answer
49 views

Qemu - debug new syscall

as a school project I have to add a syscall to the latest stable linux kernel. I did and recompiled the kernel using make defconfig and make. After going through several tutorials to boot the kernel ...
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1answer
106 views

Error compiling kernel using guide provided on Raspberry Pi website

I'm encountering errors while trying to compile the kernel from source. I've looked around but I'm not finding anything that deals with the error I'm seeing specifically. I am using the guide on the ...
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The Linux kernel: breaking user space

I started thinking about this issue in the context of etiquette on the Linux Kernel Mailing list. As the world's best known and arguably most successful and important free software project, the Linux ...
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Create Wheezy UML filesystem

I'm trying to create a Debian Wheezy filesystem to use in User Mode Linux. right now I'm following this tutorial. The commands after # Remove the other terminal events don't work here and I can't find ...
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218 views

Virtualbox and GPU Pass-trough: Device with host PCI address already attached to this VM

I have server with several GPUs. My idea is to attach them to different VMs in order to use that VMs in CUDA (or OpenCL) calculations. My setup: CPU: Intel Xeon E5-2670 GPUs: 1 x Radeon HD 7970 ...
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fglrx kernel 3.18.22

I'm trying to compile kernel 3.18.22 and while the kernel successfully compiles I can't get Catalyst 15.9 to work. According to AMD's website it should work with anything up to kernel 3.19. The driver ...
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65 views

system user + kernel time using /proc/stat

user: normal processes executing in user mode nice: niced processes executing in user mode system: processes executing in kernel mode idle: twiddling thumbs iowait: waiting for I/O to complete irq: ...