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.

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12 views

Failed when binding the blox,neo-6m driver to uart 1 on BeagleBoneBlack-wireless

i'm trying to bind the gnss driver ubx neo6m to my sensor mapped on uart1 Source of the driver kernel 5.10.23 : : https://elixir.bootlin.com/linux/v5.10.23/source/drivers/gnss Source of the DTS i'm ...
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SCHED_BATCH, SCHED_IDLE and SCHED_OTHER controversy

There are several scheduling options in Linux, which can be set to a process with the help of a chrt command line. And I can't seem to grasp one of them... SCHED_FIFO and SCHED_RR are basically real-...
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Linux-hardened kernel for Ubuntu?

I recently discovered linux-hardened, a kernel that is tweaked for extreme security. Weirdly, I haven't found any way to install it on Ubuntu-based distros. I haven't found any PPA or repo. Is there a ...
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Two different function prototypes for Linux kernel module ioctl

As pointed out in this question, the prototype for the ioctl function inside a Linux kernel module is: (version 1) int ioctl(struct inode *i, struct file *f, unsigned int cmd, unsigned long arg); or (...
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Is memory deep power down (LPDDR mode where memory contents are not retained) supported in Linux?

I recall knowing LPDDR consumes less energy, recently I've read more details: https://www.powersystemsdesign.com/articles/performance-vs-power-in-off-chip-ddr-sdram/22/5893: Deep power down: Mobile ...
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How can I keep file-backed executable pages evicted from RAM in Linux?

I tried using madvise(MADV_DONTNEED) and verified with /proc/pid/pagemap that pages are unmapped correctly. Although none of the functions in the page is accessed, some of the pages are mapped back ...
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Linux Kernel Config of Device-tree Location

I have got access to a linux kernel sources, where it has .config file in root source directory, after created it using make xxxconfig and built successfully, so can you tell me how can I find the ...
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Changing USB audio interface clock source from sync to async

I've recently acquired a new USB microphone in order to improve the audio quality of my work meetings. It sports a Cmedia CM7030 chipset which is still very new at this point in time. How do I know ...
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How do I initialize the framebuffer in my init executable?

I have a "Minimal Linux" experiment where I have to take a system as close as possible to the bare kernel and thus I need to write my own init. I know how to do the shutdown, reboot, and ...
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What kernel settings or configuration do I need to look at for a kernel that will never refuse to suspend?

Sometimes my laptop refuses to suspend, and overheats in its bag. This has been an ongoing issue with some versions of Linux over the years. Usually the reason is nfs shares, other times Wi-Fi or ...
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How is simultaneous i2c bus access handled by Linux kernel?

I have two sensors with different slave addresses connected on an i2c bus in my custom board. If two different programs try to read the different sensors a same moment of time, will it lead to an ...
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What constraints (if any) are there on network interface names on linux

In https://stackoverflow.com/questions/24932172/what-length-can-a-network-interface-name-have, it was asked how long a network interface name could be (apparently 16 bytes). However, the answers to ...
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Why can't user process READ memory in kernel address space?

It seems fairly obvious why user processes can't write or modify data on kernel address space. But I can't get my head around why they can't even read the data. I know that a segmentation trap would ...
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MCP251x driver missing

I'm trying to install the mcp251x driver on a Linux system with kernel 4.9.253-tegra and I used the command: # modprobe mcp251x I checked with the command # dmesg | grep mcp251x but it doesn't ...
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RHEL 8 Bond Interface SOF_TIMESTAMPING_TX_SOFTWARE

I'm trying to setup ptp4l over a bond interface configured with mode=802.ad (Dynamic link aggregation). When I run ethtool -T bond0 it reports SOF_TIMESTAMPING_RX_SOFTWARE SOF_TIMESTAMPING_SOFTWARE ...
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what happens when copy files across two different file systems

There is one problem after learning the file system in Linux kernel, what happens when copy files across two different file systems. Since we could use mount -t ntfs DEV_BLK MOUNT_POINT to mount NTFS ...
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Adding new flags to custom Linux kernel

Recently, I've been trying to add a new flag to a custom Linux kernel that'll be used by mmap for educational purposes. I've successfully compiled and installed the kernel with this addition but the ...
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shmat returns error (void *) -1 in selinux enabled rhel environment

as per the documentaion:- If SHM_RDONLY is specified in shmflg, the segment is attached for reading and the process must have read permission for the segment. Otherwise the segment is attached for ...
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Creating Kernel Module

I am currently reading a book on Linux Kernel Module Programming - https://tldp.org/LDP/lkmpg/2.4/lkmpg.pdf and I am running into a compilation error when running make. /* hello.c − The simplest ...
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Creating LKM using Makefile

As of lately, I have decided to begin learning about OS kernels and came across a few resources to aid in my learning process. Following the tutorial, I setup an Loadable Kernel Module and Makefile, ...
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Why do many LTS/enterprise Linux distros ship with non-LTS kernels instead of LTS ones? [closed]

The current LTS kernels from The Linux Kernel Archives are 4.4, 4.9, 4.14, 4.19, 5.4 and 5.10, so I find it interesting that Ubuntu 20.04 started with 5.8 and is now on 5.11, while RHEL 8.4 is on 4.18....
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If the Linux kernel has already selected the major and minor device number when generating a uevent, isn't it too late for udev to load a driver?

I've been trying to understand the precise order of operations when connecting a device to a computer. My understanding was that udev rules were supposed to handle some configuration dynamically, ...
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In Unix, what it means by "Everything is a byte stream"?

I am a newbie to Linux and while exploring around file system - I quite often encounter the phrase "Everything is a file". I do see an answer to this question here but I am still failing to ...
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Full form of Linux? [duplicate]

I was curious to know if Linux is short for anything, and I came across these web pages: geeksforgeeks.org/linux-full-form byjus.com/full-form/linux-full-form ostoday.org/linux/what-is-the-full-...
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Linux kernel register_chdev returned value

This video shows an example Raspberry Pi Linux kernel module which creates a new character device. It uses the kernel API register_chdev. In a comment to the video (I can not generate a direct link to ...
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How do you remove a defunct process without rebooting?

Everything I have read says "you don't need to get rid of a defunct process, they don't cause any problems." This is 100% incorrect. Today I had a process become defunct for an unknown ...
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Do I need to unbind driver on embedded device?

I've been having an issue reading from gpio devices on an embedded device(usrp n310). I2cdetect gives "UU" for the particular devices that I'm trying to reach indicating that the devices are ...
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What exactly is a single "atom" in a standard stream in linux?

Conceptually, a stream is a sequence of "characters" or "atoms", i.e. a binary stream is a sequence of 0s and 1s. But in Linux standard streams, if I write a bash script that asks &...
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How to check/set "kernel timezone" for use with iptables "time" module?

The iptables -m time module supports time-based firewall rules. By default it operates in UTC but with --kerneltz parameter it should work in "kernel timezone": $ iptables -m time --help ...
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Can't compile linux kernel with -Og/-O0 option for debugging purpoces

Having custom hardware running embedded Linux (OpenWrt) like a charm. CPU - is IMX6ULL (ArmV7) so it is supported by Jlink to debug over JTAG interface. Starting GDB server and step by step debugging ...
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101 views

unknown filesystem type 'fat32' when trying to mount /boot

i was trying to do a modification to my gentoo kernel, and while i was doing the installation i got this error when trying to mount /boot, "unknown filesystem type 'fat32'." i looked around ...
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How do I find out which toolchain to use to compile a linux kernel for an ARM processor?

I am trying to build the linux kernel for an Orange pi 2g-IoT board I am following the instructions in their official manual I have followed all the instructions in page 61 section 5, under Compile ...
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What does LOADADDR=0x20008000 mean in linux kernel make command?

I'm learning about u-boot. using qemu model, I could (using qemu) load the Image on memory location I want and I could run the kernel booting using booti addr command. As you know in arm64, there is ...
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52 views

No ethernet or wifi settings on Fedora/Ubuntu/Elementary Linux Fresh Install

My issue seems to be related to my Asus Zephyrus G15 having a Mediatek 7961 Wifi/Bluetooth adapter. I have read the posts where the support for this specific wifi adapter has been fixed in kernels 5....
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65 views

sudo apt-get update Error writing to output file - write (28: No space left on device) [IP:]

I am not a linux admin by no means and I cant seem to figure this one out. So I am ultimately trying to perform an update but running into a "Error writing to output file - write (28: No space ...
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33 views

What constitutes a new major revision (the first number in the version) in the Linux kernel?

Wikipedia says The jump from 2.6.x to 3.x wasn't because of a breaking update, but rather the first release of a new versioning scheme introduced as a more convenient system. but it doesn't provide ...
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Unable to see device register when running dmesg command

I am compiling the below code #include <linux/kernel.h> #include <linux/module.h> #include <linux/miscdevice.h> unsigned long js,je,diff; static int sample_open(struct inode *...
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54 views

'cannot attach kprobe, probe entry may not exist' when execute trace-bpfcc

I am following bcc Tutorial and trying to execute the trace-bpfcc command: sudo trace-bpfcc 'sys_execve "%s", arg1' The command fails with an error: cannot attach kprobe, probe entry may not ...
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53 views

Stuck on old gui?

Kali Linux 2021.3 I had been using the updated xfce GUI, the one released in 2020/21 I believe then when I was playing around with linux I must've messed it up because I believe I have reverted to ...
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443 views

how to install libc6 2.34 from sources?

I'm running Linux Mint 20.2 Uma and I'm trying to upgrade the linux kernel version. I want to install the kernel version 5.15rc3 but the problem is that after I download the .deb packages from the ...
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To Modify the ubuntu kernel third party drivers

We have a custom board with PCIe connector. eMMC is connected to the PCIe. So we are planning to use the linux kernel third party driver sdhci-pci-core.c and sdhci-pci-data.c which is present in ...
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linux kernel cannot find init

I'm running Linux kernel 5.14 with u-boot on a custom ARM board with 32MB of ram and 1GB micro-sdcard. this proves that I have the init files in my rootfs: (u-boot command-line) U-Boot > ext4ls mmc ...
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54 views

Linux kernel - Find current process (task_struct) by pid [duplicate]

I have read this post. But my question is the CURRENT process, not any process (find using pid). Since I can't find any documentation except from code (i.e: this) about how to use provided function, ...
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/proc/diskstats disk time spent writing more than 1000ms*CPU-core-count per second

I'm interested in how could one interpret the results of procfs-diskstats. It looks like an API, but I see no exhaustive explanation in Internet or man pages or Linux kernel Documentation. There is a ...
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52 views

How does access_process_vm() work in linux?

AFAIK, the ptrace syscall uses access_process_vm to read data from other process. However, different process' address space are isolated, how is that achieved?
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Cant locate kernel modules that I want to disable

So I was installing KISS Linux (a source-based distrobution similar to Gentoo) and while compiling my kernel, I noticed some modules that I didn't remember enabling (I wanted to install without an ...
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27 views

Unable to build Linux kernel module out of static driver code

I am trying to build a kernel module (.ko) out of a driver that doesn't have module configuration by default. I want to avoid having a built-in driver because I get firmware loading errors. I did the ...
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26 views

Unable to Get Kernel Crash Dump on Kernel Panic

I'm using kexec-tools to get a crash dump of kernel on kernel panic. However, when I trigger the panic using sysrq-trigger, the system freezes. I have to power off and then power on to restore the ...
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how can i install kernel on centos7

​​hi. I have a Centos7.but I want to install a specific kernel version like this. 3.10.0-962.3.2.lve1.5.61.el7.x86_64 How can I install that version and boot from the above kernel?
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Compilation order when cross compiling Linux

I've been following the Linux From Scratch book and just need to fill some gaps in my understanding of cross compiling Linux. Where a toolchain has already been built for the target machine, is the ...

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