Questions tagged [kernel]
Everything about Unix kernels: development, configuration, compilation, design, etc.
3,614 questions
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Why does Linux CFS need a periodic timer interrupt more frequent than the time slice?
OSTEP says
Note that CFS utilizes a periodic timer interrupt, which means it can only make decisions at fixed time intervals. This interrupt goes off frequently (e.g., every 1 ms), giving CFS a chance ...
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Curiosity: it looks like a second Power-on self test or init (like the BIOS POST does at boot) is happening after the GRUB O.S. selection? What is it?
Glad to a new keyboard and a mouse that have plenty of lights now, I've noticed this:
When I turn on my computer the BIOS Power-On Self Test (POST) happens. And I can see that my mouse and keyboard ...
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file-nr keeps increasing forever
I have a cloud VM running linux-yocto 6.17 and a few daemon processes--postfix, dovecot, rspamd, nginx, sshd, fail2ban and redis.
Ever since upgrading from 6.11 to 6.17, I've noticed that /proc/sys/fs/...
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Can I deny the root access to the user keys in the Kernel key retention service?
I know the Linux kernel has a key retention service even though I haven't used it myself.
I'm constructing a system where anybody with root cannot check the keys in that service that were registered ...
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How to set charging threshold of a Toshiba laptop directly from Linux
I just had to order a new battery which died after just one year of usage. Apart from the cost, this is a bit environmentally wasteful - waste of lithium and rare earths. So now I have learned that ...
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Is changed LVM device info not fully updated in kernel? Any workaround? Is this a bug?
My system is working just fine. The questions at the end of all this are;
does the kernel keep a cache of device information;
is it possible for it to be only partly updated, leaving a mix of new &...
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Fast question about gnu-libre kernel
This kernel is identical to Linux official kernel but they remove all proprietary binary firmware and there is not possibility to load it, this mean more safety and more os.
https://linux-libre.fsfla....
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Linux Mint 22.2 kernel problems - pc stucked when it is charged on
A few days ago I found several issues regarding the kernel of my PC.
I have a Lenovo LOQ 15IRX10 with BIOS version R3CN39WW, cpu 13th Gen Intel© Core™ i7-13650HX × 14 and GPU NVIDIA® GeForce RTX™ 5070 ...
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kernel panic after suspend starting from kernel 6.16
I've a problem with kernel versions starting from version 6.16. it was working in kernel 6.15.
In kernel 6.15, when I put my laptop to sleep and resume from it, the Wi-Fi does not resume. So I am no ...
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Ubuntu Kernel build & install problem
Running on Ubuntu 24.04, trying to rebuild the existing 6.14.0-33 kernel with some modifications I need around RT & Power management. I followed the instructions here : https://canonical-kernel-...
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How to interpret the refcnt field in /proc/crypto?
Here's an example /proc/crypto entry:
name : md5
driver : md5-generic
module : kernel
priority : 0
refcnt : 1
selftest : passed
internal : no
type : shash
...
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rsyslog holds on to dirty pages and does not flush pages to disk
We have kernel dirty bytes settings configured as below.
vm.dirty_background_bytes = 262144000
vm.dirty_background_ratio = 0
vm.dirty_bytes = 0
vm.dirty_expire_centisecs = 0
vm.dirty_ratio = 10
vm....
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Cross compile for ppc64 kernel, no way to generate Debian package?
I start to cross-compile a kernel for an old ppc64 machine using a fast amd64 machine.
I have installed all deps
apt -y install bash-completion make build-essential linux-source bc kmod cpio flex ...
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Difference between modular and built-in support in the kernel
Context
When I was configuring a wireless interface support for my Wi-Fi card, I used the following page on Linux Wireless documentation website.
It is said that I should enable Qualcomm Technologies ...
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ps ax and -o fd
According to ps(1), ps doesn't support fd.
even I didn't find fd in task_struct of kernel.
How can I find fd of a program?
َUPDATE:
FD means File Descriptor.
When I get query from services such as :
...
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How can I ascertain which kernel (not version; kernel) is in use?
I want to be able to ascertain what kernel is in use across modern, UNIX-derivative OSes.
This appears feasible, considering that utilities like uname exist on multiple OSes with different kernels. ...
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Process Maps in s390x linux systems
So I am working on a debugger for linux s390x system and have the whole disassembler etc set up for reading the ELF file. For debugger I just run it on the process with base address from the process ...
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Is there a specialized OS for container orchestration?
Containers are intended to solve the "it worked on my machine" problem. Thus, the blueprint of containers has two compatibility requirements: the OS and the architecture. We often see a ...
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linux kernel - (virtual) bluetooth device for testing
I want to test and debug linux kernel internals within the bluetooth stack, i.e. /net/bluetooth. I have a (rather minimal) kernel, manually built, with debug symbols, and a busybox at the moment, ...
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Why does /proc/vmallocinfo show userspace-like addreses?
I expected to see a list of address ranges starting with 0xffff..., but /proc/vmallocinfo gives some crazy unpadded values.
I'm cooking Mali GPU drivers for OrangePi Zero 2W, and was wondering why the ...
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How hid-generic driver catch the event from the mouse device
I have some questions regarding the hid-generic and implementing my own driver.
Below is the hid-generic source code.
hid-generic.c source code
My questions are:
How does the hid-generic driver ...
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Panfrost kernel driver on FreeBSD for rk3566?
We are two FreeBSD lovers and a stubborn system administrators.
We are trying to project a phone based on FreeBSD for several months.
Emanuel Vadot and Jesper Schmitz Mouridsen have enabled the ...
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Try netconsole in single machine, but not working
Some basic info of my machine:
# uname -a
Linux iZ2zeirtviyt9b8s96ery2Z 6.8.0-40-generic #40-Ubuntu SMP PREEMPT_DYNAMIC Fri Jul 5 10:34:03 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux
# ip addr
1: lo: &...
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Cannot set full native resolution of external monitor
I have a Thinkpad X1 Carbon Gen 12 with the following specs:
$ inxi -Fzxx
System:
Kernel: 6.14.9-300.fc42.x86_64 arch: x86_64 bits: 64 compiler: gcc v: 15.1....
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Trying to compile a tinycore linux kernel leads to Error 2
EDIT 1 - Following instructions from : https://github.com/on-prem/tinycore-kernel
EDIT 2 - after trying make os, it fails giving an Error 2 compiler error. i know that it has something to do with the ...
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How to make kernel boot real rootfs from RAM address?
I'm finding a test solution for a cpu prototype, there is no hard disk on the test platform. Now I'm searching for solutions to boot real rootfs(not initramfs) from certain RAM address.
I'm using ...
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Btrfs can see only half of the disk, bug or feature?
I think I have found a bug in btrfs, but I am not sure. At least the following script, very likely, can demonstrate it.
This script creates an 1TB big file in /tmp/btt, formats it as a btrfs and ...
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Not enough space left on /boot to remove old kernels
TL;DR :
No space left on /boot
I tried (without any success) :
sudo apt autoremove
sudo apt autoremove --purge
Removing specific old kernel
sudo apt remove --purge linux-headers-5.15.0-53
sudo apt ...
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RHEL 9 GRUB not booting automatically to the latest kernel
I have noticed a strange behaviour on some RHEL 9 servers:
GRUB does not boot on the latest kernel, despite the fact that
it is supposed to do so automatically whenever a new kernel is installed, and
...
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Is there a bug in the kernel or in the microcode for Ryzen 5 1600?
I'm using the following system:
OS: Linux Mint 22.1
Kernel: Linux 6.8.0-59-generic.
CPU: Ryzen 5 1600
GPU: GT430C
Motherboard: B450M-A II
PSU: Corsair RM850
BIOS 3002
Microcode 0x08001138
From time ...
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how do i get complete list of external firmware which is being loaded by the kernel during boot
I am compiling my own monolithic kernel for my Lenovo laptop. I am using the CONFIG_EXTRA_FIRMWARE= to specify which firmware files should be build into my kernel staticlly.
with my older laptops, it ...
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Kernel headers for 6.14.3-061403-generic not found
I have a package for a driver that I'm trying to build and deploy on 6.14.3. However the build breaks with the error:
Building for 6.14.3-061403-generic
Building for architecture amd64
Module build ...
user735142
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I want a Boot animation like Ubuntu's and can't seem to be able to get it
I've been using Debian 12 for the last couple of years and decided to give Ubuntu 24.04 a chance, first thing I noticed is that the boot animation starts at the very beginning of the boot up sequence ...
MartínVargas
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Realtek RTL8822CE WiFi not working - Pop_OS 22.04
I'm having trouble getting WiFi working on Pop!_OS 22.04 with a Realtek RTL8822CE card. It worked fine until recently but now:
WiFi randomly disconnects
Sometimes the WiFi option disappears from ...
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Why does there appear to be a discrepancy when trying to programmatically access files associated with different tasks in Linux from kernel space?
As a way to better understand Linux kernel structures, interacting with and pulling information from these (and also getting more experience coding in C), I've been building simple kernel modules to ...
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How does paging start in a kernel?
If an allocator requires paging to have been set up already, that means that paging must be setup without an allocator, no? So where is the page table put?
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PCI correctable errors on my SSD
I am on Ubuntu 22.04 LTS, and I have a Western Digital WD Black 500Gb NVME2 ssd. The laptop is a Dell E5495.
I installed a fresh Ubuntu (previously was Windows 11), but I continuosly get the following ...
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Cannot compile kernel modules on TrueNAS Scale
I have a Ugreen DXP 6800 Pro and the OS disk died. No actual NAS data was lost but I cannot figure out how to get the OS back to the same state. I was previously able to compile modules and add them ...
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When memory is allocated using kmalloc, is a virtual memory address with an already established PTE (Page Table Entry) returned?
When memory is allocated via kmalloc (i.e., slab cache allocation like slab_alloc_node), it returns a virtual memory address. Presumably, when accessing this virtual address, the corresponding PTE (...
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Kernel disappeared from GRUB after NVIDIA driver install
I'm a beginner, so I might ask some very basic questions, apologies..
I'm using a Openmediavault 7 which is a Debian 12 based NAS system with Proxmox kernel 6.11
I tried to install the NVIDIA drivers ...
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Recompiling my custom kernel and my .config is set to old config every time
I am trying to recompiling my kernel. I did a small change in drivers/media/usb/uvc/uvc_driver.c and put a pr_info() only to see in dmesg if its working.
I changed the .config file too in ...
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Kernel 6.13.* and stand-by problem
With any version of the kernel 6.13.* i’m experiencing problems after a long standby, I mean for example from 9 pm to 6 am the next morning.
Everything that is connected via usb-c docking (all except ...
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Does a .h file for external kernel modules need compilation in another, particular manner?
I have an external kernel module and a Makefile. I was using Kbuild but decided to go with a straight Makefile and make. I have my headers installed, build-essential and kmod installed, and I am ...
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Wrong attributes bitmask in READDIR requests on NFSv4.1
I'm struggling the following problem.
I have an NFS v4.1 mount, where I have a directory with a couple of thousands files. I'm trying to list their names and types. Even with a minimal example program ...
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How to set new features to N during kernel compilation from an old .config file?
I am compiling a custom linux kernel for a compute cluster. The cluster is currently running on kernel version 4.4.47 since last 5 years. I need to upgrade the kernel to a more recent version. I've ...
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Does a block device driver's queue_rq handler need synchronization with only a single hardware queue?
Reading through this tutorial and this reference, I see that block device requests go through the hardware queue before being dispatched to the queue_rq handler.
When writing a block device driver ...
- 359
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Kernel Boot custom init script and rootfs
i am using passing a script as init= for kernel boot.
I use this script to setup overlayfs using two partitions on an mmc device.
This works fine.
I use root=/dev/mmcblk0p1 as the root.
at boot, i ...
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Scheduling priority on a kernel workqueue
In the kernel I can use the work queues and create them with alloc_workqueue(...) and pass it a flag WQ_HIGHPRI for a high priority workqueue.
I also see you can use apply_workqueue_attrs(...) for ...
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Is SMI the same as managed IRQs? How can I know if a IRQ is a managed IRQ?
On the IRQ affinity tuning subject. I've realized that some IRQs cannot be reassigned to other cores.
I've read[1] that those are called "managed IRQs". On the Linux Foundation wiki, I've ...
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Changing all strcpy to strscpy
I am learning about Linux kernel development. I have cloned into the stable branch of Linux. I watched a tutorial from Greg KH on youtube that explains you can use the checkpatch.pl script to find ...
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