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

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init & System V IPC in kernel

Does it affect init if System V IPC is not compiled into a kernel? Does init require System V IPC?
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Add a module to linux kernel source code statically [closed]

I am new to linux kernel programming. I have explored that there are two ways of adding modules to linux. One way is by dynamically linking the modules with the running kernel using insmod and another ...
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Why are there no LSM hooks in the POSIX IPC APIs?

As I understand it, the Linux Security Module (LSM) framework has many hooks which are callbacks for security modules to register functions performing additional security checks before security-...
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70 views

Can the kernel symbols' addresses be influenced? consequences?

tl;dr: in my distros linux 3.08 kernel using cat /proc/kallsyms I can find out that for instance the _commit_creds function/symbol is located at address 0xc1073fe0. When either: building my kernel (...
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154 views

how to eject/unmount usb dongle logically?

We've bought a commercial application who just work only if their dongle usb is connected to the server. However sometimes the application can not recognize the dongle, so it doesn't work, but if ...
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59 views

Why does Linux have a maximum number of sound cards? [closed]

I'm specifically asking about CONFIG_SND_MAX_CARDS in the kernel. From the code using this config, for example in sound/usb/card.c for USB cards, soundcards are stored in plain arrays which are ...
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60 views

Linux kernel running only with use of physical address

Is it theoretically possible to make Linux which for its own kernel (include modules) uses only physical addresses? (it means it completely omits MMU) For processes how would you know if there was ...
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20 views

Changing the Retransmisson Timeout (RTO) estimation in Fedora

Retransmission Timeout(RTO) in a TCP plays a vital role in the internet. There are many algorithms proposed for calculating the Retransmission timeout. RFC 6298 is used for the estimation of RTO. I ...
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405 views

256 colors in console (tty)

Suppose, I have a system without X server. I can only log in from the console. It seems, by default linux console supports only 8 colors: # tput colors 8 Is it possible to use 256 colors in the ...
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62 views

Need help determining why a usb device works in Ubuntu but not ChromeOS

I am troubleshooting a problem with an Epson Brightlight 536wi projector. When you plug a USB cable from the projector into a Windows or Linux computer there is a driver built-in to both Operating ...
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55 views

OpenWRT image for OrangePi

I am looking for help on how to build OpenWRT image for OrangePi PC and|or OrangePi Plus board, preferably with working Ethernet and HDMI. I have studied related resources on the internet, like ...
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130 views

compatiblity with Intel Dual Band Wireless-N 7260 (on tablet)

I hold a Dell Venue Pro 11 7130 with the following integrated network adapter: Intel Dual Band Wireless-N 7260. My aim is using Linux in live mode on it. Most of the distros I've being running so ...
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412 views

Restrict size of buffer cache in Linux

Is there a way to tell the Linux kernel to only use a certain percentage of memory for the buffer cache? I know /proc/sys/vm/drop_caches can be used to clear the cache temporarily, but is there any ...
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39 views

WARNING: at net/ipv4/tcp.c:1654 tcp_recvmsg

Our Linux based device (3.7.2) experiencing following issue when we try to do FTP or SCP over WiFi Connection. Same will work on Ethernet Connection or on TFTP. Here is the dmesg log for this issue: ...
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18 views

DMA address mapping with physical memory

i need to physical RAM memory test, in that case i dont want to check DMA pages,how to find out DMA pages.how its allocated in physical ram ? if it is allocated in physical RAM. Testing RAm then i ...
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119 views

What does 'make localmodconfig' do?

What does make localmodconfig do and what should you set so that external hardware is supported?
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Autoloading a particular driver, based on a detected specific kernel

I need some help in writing a tiny script and determining its placement within Debian 7.9 filesystem. As the title says, the script needs to be executed automatically on startup and, after checking ...
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40 views

Building Linux driver for a network card remotely, while being connected via the same card

I realize that the title alone sounds confusing, so let me provide the context. My current Linux machine configuration is Debian 7.9 (I need this specific version) with the default kernel 3.2, which ...
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144 views

find which process is sending the current io request in linux kernel

I've been diving into the Linux kernel. and would like to trace an io request and find out exactly which process sent the current io request? There is a structure named current which the kernel ...
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25 views

adding a governor

how to add the Governor in the appropriate spot..they said"Add the following lines in appropriate spot amongst the other govenor's" Yes, they've given one code that i have to add, but how ? here is ...
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50 views

Linux Kernel is panicing on boot

After following this blog post I get a kernel panic when running: qemu-system-x86_64 -kernel bzImage -hda my.img -append=/dev/sda What could be causing this? Could I have left something out?
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900 views

“rcu_preempt detected stalls on CPUs / tasks” message appears to continue

My board continues to display the message below. The terminal does not have any input. What is it with the following message, which I know? (T, g, c, q ...) What is the cause of this phenomenon? ...
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58 views

Compiling a single kernel module which resides in the kernel tree

I have updated my Linux kernel to 4.3.3, everything works smooth except my webcam (QuickCam® Pro 9000) which is not working. According to the dmesg, the kernel recognizes the I have plugged a usb but ...
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How async_port_probe() call works in linux kernel?

To Understand the SATA device enumeration process I was studying the driver/ata/ata_piix.c which is showing as SATA host driver for my system in the output of lspci command. 00:1f.2 IDE interface: ...
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38 views

where is make_request_fn source code in linux kernel

in my study and examine linux kernel code I encountered with function make_request_fn. in this link it says that this function type definition is in include/linux/blkdev.h, line 211 : typedef void (...
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What is txqueuelen equivalent for receiving in linux?

I have always wondered that txqueuelen in output of ifconfig command defines transmission queue length in linux in terms of packets which I assume get utilized in various qdisc management while ...
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Linux Kernel module Remote Debugging with GDB + KGDB, Remote 'g' packet reply is too long

I am trying to remotely debug Linux Kernel and I am having issues. My setup: Target machine with Ubnutu Linux with my custom kernel 4.3 which I built with debugging information and KGDB. ...
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printk does not prints in terminal

I inserted some printk in kernel 3.15.1 functions such as theese: in fs/read_write.c in function read(): printk("Ata: Im in fs/read_write.c and in function read"); in same file in function ...
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103 views

Creation of the heap region/segment in Linux

It's my understanding that on Linux the process loader doesn't automatically create a "heap" region for a process like it's the case for the stack, is that correct? I used /proc/$$/maps and before ...
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1k views

What is a “subreaper” process?

The word "subreaper" is used in some answers. Searching Google also turn up entries where the word is "just used". How can I understand what a "subreaper" is?
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30 views

which section of kernel, manages io requests?

I know that the Block IO layer in Linux io stack manages and schedules io requests. but i do not know where is this code? indeed, i wanna see the section of code in kernel which corresponds to this ...
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In which thread does block driver issue commands to block device?

I'm currently reading "Understanding The Linux Kernel" book, as I've understood block I/O request order is like this; user space call => vfs call => I/O scheduler call => block device driver call. ...
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145 views

How to find the driver (module) associated with SATA device on Linux?

For one of my applications, I have to understand the the SATA device driver flow. As per my understanding, SATA device driver should be there in the Linux kernel tree. I have referred how to find the ...
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last samples are skipping when we do record and playback in loop back mode in linux

I am just connecting my output to the input of codec using mixer controls in linux. I am recording the data with tinycap in bag round and then I started playing of a 30 seconds sine tone using ...
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Linux 4.3 - Waiting for root device /dev/mmcblk0p1

I want to update my custom i.MX6 Board to Linux 4.3, but with the new Kernel the boot process stops at boot and can't load the rootfs from sd-card. With the old Kernel 4.1.x it works fine with the ...
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142 views

Porting Linux on LPC2148 board

Till now I was working with Raspberry pi, beaglebone etc. So, I am looking to do something new. So, I decide to port Linux on my LPC2148 board. But I am unable to find any tutorial regarding linux ...
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190 views

Create CentOS-7.1 custom iso with upgraded kernel-4.2.6

I am trying to create CentOS-7.1 custom ISO with kernel-4.2.6. But I am facing issues while installing. Please see attached image for details. I have followed the following steps to prepare a custom ...
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31 views

Kernel module version enforcement

Linux can be configured to require that kernel modules be digitally signed. On kernels built for embedded devices and consumer devices (i.e., tablets, smartphones, etc.), I can still see that this ...
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how to build kernel-tools-4.2.xx.rpm and kernel-ltools-libs-4.2.xx.rpm

I am trying to upgrade Centos-7 kernel (kernel-3.10) to (Kernel-4.2.6) and for that I downloaded kernel from kernel.org and create rpm for the custom configuration (arch x86_64)using "make rpm". ...
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24 views

Linux tools for perf (install linux-tools-3.15.0)

I use Linaro version of Linux (Linaro 12.11) on my embedded target with ARM9 Core. For a certain profiling, I need to use the perf tool. perf require linux-tools-3.15.0 to be installed on my device. ...
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1k views

Intel Skylake + DisplayPort 1.2 MST/Daisy chain on Linux

I am planning to buy hardware for using DisplayPort 1.2's MST feature to daisy chain two monitors in combination with the Intel Core i5 6600 Skylake processor on Ubuntu. Is this supported yet with the ...
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114 views

DKMS modules never installed properly on kernel upgrade

I have multiple DKMS modules installed on my system, some of them mine, and some of them belonging to pretty major maintained packages such as Oracle's VirtualBox 5. What I've found is that on every ...
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169 views

Remapping Apple Keyboard with Linux Mint

I like to use an apple wireless keyboard with my laptop that runs Linux Mint 17.2 Cinnamon 2.6.13 64-bit with the 3.16.0-38-generic kernel. However, I would like to remap the fn, alt, command, control ...
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118 views

Running a real time kernel on Debian

As I have Debian 8 running on my laptop, I have got some questions about making my OS a Real-Time one: Does the Debian GNU/Linux distribution have an official Real-Time version? (I found that the OS ...
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123 views

Are there more advanced filesystem ACLs beyond traditional 'rwx' and POSIX ACL?

Are there any simple and integrated (i.e. embedded into filesystem) ACL patches for Linux kernel exist at all? The problem is simple: I need something more flexible and advanced beyond classic 'rwx' ...
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70 views

SIGSEGV: 0x0000000000000000 in ?? ()

I am executing an iperf connection between two UML machines running the following kernel: Linux client 4.1.0-ga61e56d #55 Mon Nov 30 13:51:59 CET 2015 x86_64 GNU/Linux I am working on the TCP/IP ...
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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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110 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 ...