Questions tagged [linux-kernel]
Questions about Linux kernel and Linux kernel related topics eg. implementation details such as system calls, kernel customization, etc. For Linux user space topics which do not involve kernel details, [linux] or distribution tag are more suitable.
3,575
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How do Kernel use pagecache?
I am a the problem about pagecache, I don't understand. as I understand, The pagecache will serve as disk cache for reading and wring from disk. But I don't know how to kernel can map 10G memory ...
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code kernel: ACPI Error: Could not disable RealTimeClock events (20230628/evxfevnt-243)
code kernel: i8042: PNP: No PS/2 controller found.
code kernel: mousedev: PS/2 mouse device common for all mice
code kernel: usbcore: registered new interface driver appletouch
code kernel: usbcore:...
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How to disable kernel_lockdown (MSR) without BIOS or console access
I have a laptop with a damaged screen. I use it by connecting a screen via HDMI. I'm running some cryto mining software that requires MSR access to run efficiently.
I cannot access the BIOS to disable ...
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11
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TP-Link drivers on Raspberry Pi 2 Raspberry Pi OS
I have recently acquired a TP-Link 300 Mbps Mini Wireless N USB Adapter (Ver 3.0).
Naively I had hoped that using this wireless adapter with my Raspberry Pi would be a simple matter, but this was not ...
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28
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Linux kernel slab usage growing every second
Memory in Linux is filled with kernel slab memory, which is not cleared in any way.
The only thing that helps is restarting the host, but that's a crutch option.
This is slabtop:
Active / Total ...
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Can I boot Linux with root hosted on 9p (tcp) without initrd?
I searched for an answer but only found stuff related to QEMU/KVM+virtio. Don't want to use nfs because diod is far easier to config + faster.
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9
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Build Debian Kernel Package from particular commit with modified configuration
So far I figured how to build the kernel (I think) from the fork from particular commit as Raspbian OS .deb package. It's more less:
Clone the fork, switch to commit I want
Populate debian content ...
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46
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Linux memory management and cpu capacity management
I dont understand this. In early days i had one CPU, a 233 Mhz Pentium CPU with a 512 K cache, i had 64 MB of RAM. I was able to play, watch videos, got Windows working, and was able to read text data ...
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Difference in memory page fault for sequential access vs random access?
Suppose we have a range of memory values that are mapped (but not loaded), and we would like to access them. Is there any kind of optimizations the kernel does that would make the sequential access ...
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How to get full mountpoint path name by the sturct fc_context
In my kernel module, I've implemented a syscall hook named fsconfig to manage operations related to remounting readonly mountpoints. For instance, if a user executes mount /dev/sda /tmp/mytest -o ...
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36
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How to make an unofficial Orange Pi 5 Mipi-DSI display work on an Orange Pi 5 Arch Linux system, given kernel driver source and .deb package?
For a while I've tried to make use of a display I ordered from Aliexpress to make it work with an unofficial 7Ji Arch Linux distribution for Orange Pi 5, to no avail. Perhaps against my better ...
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2
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76
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WORD_BIT vs LONG_BIT
What is the difference between WORD_BIT and LONG_BIT? And which one should I use to find out the word size of my system? Both return different results
➜ ~ getconf LONG_BIT
64
➜ ~ getconf WORD_BIT
32
...
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1
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62
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How does Linux implement multitasking on CPUs which do not support multitasking?
Someone told me that Linux can run on CPUs which do not support multiple tasks.
But if you have one core only which doesn't support multitasking, how does Linux implement multitasking?
Let's say I ...
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22
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Linux Kernel cannot find USB Stick to use as root FS
I have a USB stick with a Basic Linux/Busybox distro from scratch.
I use extlinux as my bootloader.
In Qemu everything works fine and I can boot without problems by typing in the following command ...
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15
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Manually Assigning C-states to CPUs for Energy Optimization
Is it possible to manually set specific C-states for CPUs, similar to how we select processor frequencies, for energy optimization purposes? I'm interested in tools or methods that allow such granular ...
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49
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Linux syscalls: advantage of copy_file_range over sendfile?
I understand that classically, the Linux Kernel was conservative about adding new syscalls.
But, I've learned about the existence of copy_file_range, which seems to do the exact same thing as sendfile....
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Debug log from system call stat() is not printed
I want to build the 4.18.1 linux kernel and add a debug log in several places: in clone and stat system calls. I added the line printk(KERN_INFO "syscallstat"); at https://elixir.bootlin.com/...
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58
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modprobe: FATAL: Module dm_mod not found in directory /lib/modules/6.6.16
I have built a custom kernel and given a CONFIG_LOCALVERSION of -grant-nvme during compilation. However, when I try to boot into it, no matter what I do, grub seems to look for /lib/modules/6.6.16 and ...
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21
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systemtap script to simulate the IO error failed
I was trying to simulate the read/write error on specific sectors of the volumes by using the following systemtap script
global error_sector_start
global error_sector_end
global error_major
...
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Although all is correct, Linux kernel module signing fails strangely
I have a problem during signing kernel module, which is not able to sign microcodes only, other is going well.
/playground/lin/linux$ make bindeb-pkg KBUILD_SIGN_PIN=1234 -j8 V=12 1> /dev/null 0&...
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Linux kernel support of old(er) Radeon GPUs
I have a Radeon RX 6700XT and it works flawlessly in Linux.
I am looking at getting an older Radeon card and was wondering what is the support for something like a Rx 460.
Is it native as my beefy ...
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79
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procedure for updating linux kernel with a test kernel I built
Background
I have Debian linux on a Starfive VisionFive 2 SBC that I am experimenting with. The VisionFive 2 is a RISC-V SBC and Starfive provides a Github repository with all the necessary materials ...
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how to stop execlp and execvp functions, when they encounter an executable which the kernel can’t run, try running it using a shell [duplicate]
Im two years on Linux and i'm still a newbie.
after reading: (thx to steeldriver
and Kamil Maciorowski)
What types of executable files exist on Linux?
Which shell interpreter runs a script with no ...
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2
answers
121
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Linux disable RAM Cache
I'm running Debian stable with kernel 6.5 on an ARM M1 MacBook Air. The biggest issue is that RAM and VRAM are unified, and there is no particular way to even check how much of the used RAM is VRAM (...
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36
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GRUB2 and PXE: error: no suitable video mode found
I am building a diskless Debian 11 image that will load over PXE; that part mostly works, but I'm seeing this annoying message during boot:
error: no suitable video mode found.
Booting in blind mode
...
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1
answer
122
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Fedora Failing to Launch Linux Kernel 6.7.X, must boot twice to select kernel
I have a newly built desktop running Fedora 39. (I have been told it may be important to note it has an NVidia GPU). A few days ago, the following occurred:
I installed a normal system update
For ...
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21
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Is there some u-boot specific device tree?
I was reading this thread and someone mentioned a "u-boot device tree", which seems to be different than a "kernel device tree". They said:
I would make same change to uboot ...
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96
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Process memory layout - difference between heap, data and mmap areas
I see in the web many conflicting or unclear descriptions of the memory layout of a Linux process. Usually the common diagram looks like:
And a common description would say that:
The data segment ...
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1
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26
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Starting point for linux kernel update
My android device runs on Linux localhost 4.14.193+-ab517 #1 SMP PREEMPT Fri Dec 8 03:28:21 CST 2023 armv8l Android (info from uname -a). I humbly request the community for the suggestions on how ...
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83
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kworker causes high CPU and RAM consumption
The kworker performs operations that take the Memory, I/O, and CPU highly on my VPS every hour.
How can we fix this?
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70
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Custom Linux kernel build fails at loading initial ramdisk
I have been trying to build my own Linux kernel, but it keeps hanging after Loading initial ramdisk... I am currently using Arch linux, and have tried several different configs.
I tried both the 6.8-...
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2
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61
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Linux 6.7: /sys/class/graphics/fb0 is missing
What happened to this node/symlink? It used to be there for ages, linking to the primary display adapter, and I cannot find it any longer with Linux 6.7.4. I've not found anything relevant in the ...
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What is the process "pool_workqueue_release"?
What is pool_workqueue_release?
It seems it's spawned right after kthreadd, ktrheadd is the main process/daemon to create kernel threads, right?
In linux/kernel/workqueue.c I found:
static void __init ...
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1
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167
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How much of the Linux kernel is currently coded in rust? [closed]
Its a curiosity thing, but I would like to know How much of the Linux kernel is currently coded in rust ? I means in percent, and if you known it which part ? is there only drivers or is it real part ...
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How to clear old Pop OS kernels
I am currently using Pop OS, and have been for maybe a year or so. A little while ago I ran into an issue with some package versions not matching up. I looked to see how to fix it and though I ...
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137
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What reasonable value of swappiness should I config to get better performance?
In the process of optimizing the Android system, the configuration of the 'swappiness' value is crucial. The value path is /proc/sys/vm/swappiness. Some sources suggest setting it to 60, while others ...
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2
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120
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insmod fails - module does not match running kernel but module has been compiled against correct kernel
Moved from here since this is the correct StackExchange.
Goal
Recompile the NVMe driver on Rocky Linux 9 without any changes (I want to make some but right now I'm just trying to get a working module)...
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27
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ACPI BIOS error
I've had problems with my Laptop since a while now, I cant explain it that good but i can try. There a multiple problems, the first occurs when booting my Laptop (ROG Strix G513RW_G513RW 1.0), when ...
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45
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How do I fix my initramfs for booting linux kernel image on qemu?
I am using an M2 mac. I built the linux kernel in a aarch64v8/ubuntu docker container. Here's the docker-compose.yml
version: "3"
services:
dev:
image: arm64v8/ubuntu
platform: ...
2
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1
answer
59
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What does "&& n" mean in Kconfig?
I'm trying to compile Linux 6.7.2 with support for the x32 ABI and I just can't figure out what this means:
Symbol: X86_X32_ABI [=n]
Type : bool
Defined at arch/x86/Kconfig:3007
Prompt: x32 ABI for ...
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26
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Why can't linux use $ORIGIN to find the loader (aka interpreter)
When compiling a binary on Linux there's this thing called the RPATH, which tells the dynamic loader where to look for the shared objects. What I like about the RPATH is that you can vendor a ...
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Screen glitches / artifacts / flickering on all modern distros and kernels. I haven't been able to find solution for over half a year [closed]
Description of the issue:
Horizontal lines, glitches, black or white horizontal bars appear randomly on the screen. It's very, very random. Sometimes it's barely noticeable, sometimes it's like on two ...
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40
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What safety CFLAGS does the Linux kernel use?
I have seen it said that the Linux kernel is built with -fwrapv to define signed integer overflow as wraparound, potentially sacrificing a tiny bit of performance in return for preventing the ...
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1
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Count the total processes spawned using /proc/loadavg
In a Red Hat Linux 8 operating system, I examined the output of cat /proc/loadavg and obtained "5.20 5.78 8.04 16/1596 1954863".
After 4 minutes, I rechecked the /proc/loadavg output and ...
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47
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How to grant setuid permission to sudo
So, I'm building my own Linux distribution and I've set up quite a lot, including sudo. Working from a shroot environment, sudo works well, the problem is when i actually boot into my distro. ...
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1
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32
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How to switch to boot device's root file system from initramfs
I've been working on an operating system using the Linux kernel. I've successfully compiled the kernel and can boot into my initramfs through it.
The issue arises when I try to switch from initramfs ...
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87
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I Failed to execute AARCH64 Linux kernel on the QEMU
I'm trying to execute AARCH64 Linux kernel on the QEMU.
But,there was an error and the error log is:
rom: requested regions overlap (rom bootloader. free=0x00000000422c0a00, addr=0x0000000040000000)
...
4
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1
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149
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Which filesystems support the C attribute?
On BTRFS filesystems you can disable CoW for a file using the C file attribute, like this:
chattr +C filename
I expected this to work on ZFS too, since it is also a CoW filesystem, but the attribute ...
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0
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43
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Linux USB gadget configured through configfs
I have successfully configured USB On-The-Go (OTG) on an STM32 MPU (Linux) to support both Abstract Control Model (ACM) and Human Interface Device (HID) protocols. I utilized the ...
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How does Kernel Clock Rate matter in network emulation (by netem)?
I want to use network emulation (netem) on a PREEMPT-RT kernel to emulate latency and jitter down to 0.5 ms +- 10 %.
Thus, I initially thought that I have to adapt the internal kernel clock rate to at ...