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Questions tagged [kernel]

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

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How does Linux actually perform protocol data unit (PDU) encapsulation?

I understand that as data goes from the upper layers (Application Layer) to the lower layers (Physical/Link Layer(s)), the data is encapsulated. When it goes back up the layers, it is decapsulated. ...
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RBP 3+ Stuck at rainbow screen after LUKS encryption

I'm trying to create a raspberry pi with kali linux that is encrypted with a key that is located on a USB device, so it doesn't boot without the USB device plugged in. I followed this guide: https://...
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1answer
45 views

Keyboard issue console terminal

I have an issue on my Debian computer with Intel Stick. Link to screenshot => I have extra character in console tty like ^[ This issue is only with supperior 4.11.12 kernel Debian kernel and 4.11....
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Can I generate a single device tree dts file from all the files in my device kernel?

I need to fix a driver that is using a node in the device tree, the problem is that the node and it's aliases are all over the place, separated through few different files with few overrides and it is ...
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1answer
58 views

how to acheive: minimum kernel processes and minimum userland processes?

Basically, I want to have an embedded-linux to run a single application, but with minimum kernel process and minimum userland process: I don't really care the size of kernel or root file system. (...
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Communicating between userland and kernel space (KEXT) on MacOS

In order to make it easier to develop a kernel module, I am considering Loadable kernel modules (LKMs) on MacOS. This way you have a base kernel module and your main kernel module which is an LKM ...
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1answer
19 views

How to log every instruction and change in memory in any process

I read here this: Falco depends on a kernel module that taps into the stream of system calls on a machine and passes those system calls to user space. (Emphasis mine). That hints at the ...
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The things that can run in kernel-land [closed]

I learned that you can write device drivers that run in kernel land, and am now wondering what other sorts of (major/important) things you can do at the kernel level that you can't do at the user-...
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How to get notified of a USB plugin and manually specify the driver to use

I am trying to get at the bottom of how to intercept when a USB is plugged in, so that you can completely customize the experience of plugging it in and using it. Without anything else happening. That ...
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add intel driver module to initram for pxeboot

I'm triying to boot system-rescue-cd via pxe. The Problem on the actual system is, the driver for the network card (intel 82574L) e1000e is not in the initram.igz file, so the system can boot the ...
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1answer
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How to disable retpoline?

I need to disable retpoline for a use case. I tried adding noretpoline to the boot parameter but it doesn't seem to work. The output after adding noretpoline param: $ cat /sys/devices/system/cpu/...
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How to verify a kernel module signature?

When you compile a kernel source, you can choose to sign kernel modules using the CONFIG_MODULE_SIG* options. The modinfo tool should handle the task of verifying the module signature, but there has ...
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data race within ptr_ring code implementation

I am implementing single-producer,single-consumer ptr_ring buffers. Are there really data races within this linux driver code ? I asked this because ThreadSanitizer gives me error and my system ...
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2answers
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How can I avoid my boot and kernel partitions getting out of sync?

I apparently screwed up my Arch Linux system by inadvertently updating the kernel, but not the boot partition. So, for example: pacman -Q linux -> results in 4.20.arch1-1 uname -a -> results ...
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2answers
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Rootfs versus kernel confusion [closed]

I know that they are two different entities. Rootfs is a file system which describes how to store and access data. The kernel is actual code which executes. However, isn't the kernel code stored ...
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1answer
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A procedure of caching data in linux kernel, especially on LLC

I wonder how kernel puts data on LLC or L3 caches in detail. I have been searching the information about using cache in kernel but many results talk about page cache or buffered cache but in this ...
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1answer
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Access grab state of evdev device

I need to retrieved the grab state of an evdev device in a program. More specifically, I need to retrieve the state of the grab pointer in the evdev struct seen here: https://elixir.bootlin.com/linux/...
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1answer
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Compiled kernel 4.19 will not boot: “Kernel panic not syncing : System is deadlocked on memory”

I am compiling kernel 4.19 on Ubuntu 14.04 because I have a assignment to add a system call, but when I try to boot this kernel there's a error: Kernel panic - not syncing: System is deadlocked on ...
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1answer
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Have to rmmod and modprobe every time I start up

I have got a raspberry pi and I've installed it correctly the 8821cu module for my Wi-Fi Dongle and it works ok. But every time I reboot the pi I have to sudo rmmod 8821cu && modprobe 8821cu ...
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Unable to read SD cards linux

I'm unable to read any SD card from Linux. I already tried both SD cards that I have here in different machines (windows and Linux) and they work flawlessly, I also booted from a live USB (the same ...
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0answers
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Reduce used display size for both X server and console

I have the situation that I have a LCD display that I would like to use but I want to have a "black unused frame" around the displayed content. Is there a kernel setting which controls the used ...
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0answers
36 views

“make xconfig” raises a Qt error

When I call make xconfig in my linux kernel source directory, I get the following error scripts/kconfig/qconf Kconfig Gtk-Message: Failed to load module "canberra-gtk-module" Qt: Session management ...
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Can not Mount “/dev/hdb on /cdrom” on Carrier i-Vu CCN

I had to replace a hard drive in a Carrier I-VU HVAC Control server for a nursing home with no heat. I am not a HVAC guy but am trying to get heat back on because repairman could not get it for a week....
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0answers
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How differently from Linux kernel does a typical Unix kernel (System V, Free BSD, …) implement processes and threads?

In my previous post, about the Linux kernel, the structure task_struct represents threads i.e. light weight processes, but not processes. processes are not represented by any structure, but by ...
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compile and use a realtime kernel on CentOS 7

I would like to compile and use a realtime kernel on CentOS 7. I found a guide on the web: http://jensd.be/589/linux/complile-and-use-a-realtime-kernel-on-centos-7-or-rhel-7 When I try to use it I ...
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0answers
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Are .text sections shared between loaded ELF executables?

If one program, for example grep, is curretly running, and a user executes another instance, do the two instances share the read-only .text sections between them to save memory? Would the sharing of ...
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2answers
32 views

kdump in CentOS 7

I wanted to migrate to CentOS 7.5 from CentOS 6.9. during installation I saw an option kdump that i could enable or disable. I wonder what is kdump and disabling it has any bad effect on server? I ...
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0answers
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FIPS integrity test failed on RHEL 7.5 with 4.X kernel

I have a Dell PowerEdge R7425 with Intel NVME P4500/P4510 NVME drives. On the 3.10 kernel, the NVME drives throw I/O errors very frequently, and these errors have led to a system halt once already. ...
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0answers
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About `page_table_lock` in Linux process address space

I'm reading a tutorial about Linux page table, in the linked page Each process has its own page tables (threads share them). The pgd field of the memory descriptor points to the process's page ...
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1answer
172 views

Kali Linux kernel headers for 4.14.71-v6

I am trying to install kernel headers version 4.14.71-v6 (uname -r) for Kali Linux. I already did the common commands... apt update apt upgrade apt dist-upgrade apt install linux-headers-generic alt ...
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Kernel panics only with ACPI enabled

I have ubuntu 16.04 on my laptop. It was working good until few days ago. The system won't boot. It logs ACPI errors and then kernel panics: ACPI Error: No handler for Region [RAM_] ( (ptrval)...
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1answer
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Do rolling release distros like Arch Linux include kernel upgrades as part of their rolling upgrades?

Do fully rolling_release distros like ArchLinux, openSUSE, Alpine and so forth include kernel-upgrades as part of their rolling upgrades? Or kernel upgrades are a separate issue even within the ...
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1answer
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How to Install or Upgrade to Kernel 4.19 in CentOS 6

# lsb_release -a LSB Version: :base-4.0-amd64:base-4.0-noarch:core-4.0-amd64:core-4.0-noarch:graphics-4.0-amd64:graphics-4.0-noarch:printing-4.0-amd64:printing-4.0-noarch Distributor ID: CentOS ...
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2answers
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Why /proc/meminfo shows MemAvailable under Kernel Version 3.10?

I've been using CentOS 7 and its kernel version is 3.10. To check Kernel Version, I typed 'uname -r' and command showed 3.10.0-957.1.3.el7.x86_64 As far as I know, MemAvailable metric was introduced ...
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1answer
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Resource locking in interrupts

I have a kernel module with netfilter hooks at different points in the packet route, and the hooks use shared resources. In addition, the module has a char device that may be written to, that also ...
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0answers
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What happens to memory that wasn't freed in a kernel module after unloading?

Suppose I called kmalloc and didn't free that memory before rmmod was called on the module, what happens to that memory? Is it a memory leak and it is completely unusable until restart, or does the ...
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1answer
26 views

mismatch between kernel version and kernel header

I use an embedded with a bit old kernel 2.6.37. Now we need to update rootfs with more update gcc than the one used on building the image (Instead of 4.3 need to use 5.1, because it will support c++11,...
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GUI won't boot after package update: Restoring Resolver State [closed]

Linux Mint Rosa dual boot with windows 10 Nvidia GTX 870M Suddenly can't get to Linux Mint gui after running a package update to upgrade python. Everytime I login it kicks me back out. flashing this ...
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2answers
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Can kernel upgrades be done with configuration management (CM) tools for above-OS software?

I use various Linux Distros, mostly Debian-based, usually all default (I change nothing in the kernel/shell or internal-utilities (utilities that come with the distro). I usually install Apache, MySQL ...
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1answer
31 views

Linux kernel module development buildroot

I have build a linux kernel for the beaglebone black using buildroot. Now I would like to develop a hello world linux kernel module application: #include <linux/init.h> #include <linux/...
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1answer
61 views

When the operating system shuts down, how does a service manager know that it should sends SIGTERM and SIGKILL to its services?

Reading one of Stephen's excellent replies, When the operating system shuts down, processes are shut down using SIGTERM and SIGKILL, but those signals don’t come from the kernel (or not directly — ...
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2answers
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What is the difference between “when the operating system shuts down” and “when the kernel shuts down”?

Reading one of Stephen's excellent replies, I was wondering what differences are between When the operating system shuts down. ... and When the kernel shuts down, ... (... I’m considering that ...
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0answers
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correct circular buffer API usage [migrated]

I need to correct circ_buf.c which gives out these long errors ? The most common error is error: invalid type argument of unary ‘*’ (have ‘int’) For more context, please see this reddit thread /* *...
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1answer
26 views

What are the benefits of using longer/shorter periods in cpu.cfs_period_us?

When you want to limit CPU time per process, you can do it via cgroups. There are two parameters that can do the job: cpu.cfs_period_us and cpu.cfs_quota_us. There's some info on the parameters here: ...
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1answer
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Elan touchpad: Kernel Config

I'm running Gentoo Linux on an Acer Chromebook 15 (CB5-571 auron_yuna) and I have a minimal kernel configured supporting everything I need except for my Elantech touchpad. I've read a bunch if other ...
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1answer
59 views

Lenovo Thinkpad Mute LED Stopped working after update

Updated my packages today on my Lenovo Thinkpad X1 Carbon (6th Gen). I didn't expect anything to happen but it did. The Mute indicator LED's on the F1 and F4 key stopped working. I actually know this ...
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0answers
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Lifespan of blocks in a UNIX block-cache

Recently, I've been getting into OS development and have been experimenting with writing my own small kernel. I've just begun to look understand and implement a block-cache, for caching data read from/...
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4answers
820 views

Why does the kernel even bother to send SIGKILL? [duplicate]

If a program is not allowed to handle or ignore SIGKILL and SIGSTOP, and must immediately terminate, why does the kernel even send the signal to the program? Can't the kernel simply evict the program ...
3
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1answer
41 views

Why are du -h / du / df / df -h not refreshing when extracting a large file

I am running tar in the background, eg: tar xfvz large_file.tar.gz & It does extract my file, but when I then launch du -h, du, df or df -h, the output remains the same, and I have to wait ...
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Recompiling kernel to reduce vmlinuz size to less then 5-6mb

I am compiling kernel for my Ubuntu to minimal but every time i compile i am getting uuid not exists dropping to shell ERROR (if my kernel size is less then 8mb).. My minimum Size is 4.7mb but still ...