Questions tagged [kernel]

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

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Docker on visionfive2 risc-v

Docker on visionfive2 risc-v user@starfive:~$ sudo dockerd WARN[2024-03-02T13:08:27.753708638Z] Unable to find memory controller WARN[2024-03-02T13:08:27.753772888Z] Unable to find io ...
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Laggy PC with Kernel 6.5 and AMD 5500U Lucienne

I am currently facing a problem with my Lenovo E15 laptop (AMD Ryzen 5500u "Lucienne" processor) and the kernel 6.5. (Xubuntu 22.04) Maybe 3 weeks ago, I noticed that my computer was having ...
1 vote
1 answer
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Multiple distros crash and reboot when trying to resume from sleep/suspend on laptop

Gigabyte Aorus 15 XE4. Nvidia RTX 3070ti. After multiple attempts, this doesn't seem to be related to Nvidia Drivers or intel/nvidia optimus like I thought based on many people with a similar issue. (...
30 votes
2 answers
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Do I need root (admin) permissions to run userspace 'perf' tool? (perf events are enabled in Linux kernel)

Do I need to have to run perf userspace tool as system administrator (root), or can I run it (or at least some subcommands) as an ordinary user?
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Alpine Linux 3.18.3 - Kernel pinning during installation

I'm a new Alpine Linux user and I'm struggling to install a specific kernel version on Alpine-virt-3.18.3-x86_64. The ISO I'm using comes with the default kernel version 6.1.43-0-virt. When I run the ...
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Repeated crashes on Debian 10

I have a dedicated machine in my garage running LinuxCNC on Debian 10. Recently it's been having repeated crashes and rarely lasts longer than 30 minutes before freezing. I've tried Ctrl-Alt-Del and a ...
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1 answer
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ethtool problems [closed]

I am using a beaglebone black which has Debian 11, kernel 5.10 .168-ti-r71. I also have a GSM Modem connected to it, SIM7000E. I am trying to do a PPP connection. Weeks ago when I tried it I had no ...
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1 answer
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drm-kmod-20220907_2 not supported for this configuration / NVIDIA : Failed to initialize the NVIDIA kernel module

I need to conduct some tests on top of the FreeBSD 13.1. So,I've installed it on one of my disks. I've installed xfce4 and KDE,Xorg and from the ports (after having upgraded them). I've installed the ...
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3 answers
2k views

How to print dmesg output to host machine from qemu guest vm

Command Here is what I am doing # Step 1. In host machine $ qemu-system-x86_64 \ -enable-kvm -nodefaults -nographic -L /usr/share/qemu \ -m 8G -smp 4 -boot c \ -netdev user,...
38 votes
3 answers
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What does the vm.swappiness parameter really control?

Per the kernel documentation: This control is used to define how aggressive the kernel will swap memory pages. Higher values will increase aggressiveness, lower values decrease the amount of swap. ...
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1 answer
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Is it safe to disable Frequency Scaling and CPU idle Power Management support for Real Time purposes?

I'm using a Raspberry Pi board and I would like to build a real time system. During the kernel configuration, I found the CONFIG_CPU_FREQ option, which (from the help section) allows you to change ...
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2 answers
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Kernel parameters are not changed permanently for RHEL7

Trying to permanently change some vm kernel parameters, I created /etc/sysctl.d/01-custom.conf config file as it described in Red Hat knowledgebase article. Here is its content: # cat /etc/sysctl.d/...
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Completely confused with vmstat

So, from what I've found, there are multiple versions of vmstat out there for various OSes like Linux, BSD, and Solaris. I'm referring to Linux's vmstat procps-ng 3.3.17 . Now, to be more specific, ...
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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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1 answer
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(Why) does the Linux kernel use an identity mapping for its virtual address space?

I am currently researching the Linux kernels usage of virtual address spaces. I understand the benefits of having those, how page table walks work in x86, and the layout of the virtual address space. ...
2 votes
2 answers
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Identifying physical network devices using /sys/class/net/<iface>

I wanted to know if there is a way to differentiate physical and virtual network devices. ip a doesn't have an option. So I am trying /sys/class/net/<iface>. There are 2 attributes ...
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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 ...
3 votes
2 answers
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Where can I find older kernel documentation?

I am trying to find kernel parameters documentation for v3.10 on the internet. I was able to find the latest version here: https://www.kernel.org/doc/html/v5.0/admin-guide/kernel-parameters.html back ...
3 votes
1 answer
2k views

Remove the new kernel

I was working without any problem and one day the computer didn't start he said that there is a problem in the Xserver , so I connected to my computer through ssh and reinstalled xserver-xorg ,xserver-...
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EVE-NG installation missing build folder from /lib/modules/kernel

I have EVE-NG ISO installed on a laptop and I'm trying to install a realtek driver for the wifi-card and I have to use 'make' to compile the code. 'Make' fails with the error message: "/lib/...
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1 answer
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Debian file corruption bug possible without reboot after unattended kernel update?

Today I learned that there had been a faulty Debian kernel version which caused ext4 data corruption (bug 1057843) in December 2023. Searching through the /var/log/aptitude and /var/log/apt logs, I ...
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nvidia-driver-515 throws error on kernel 5.15 inside Ubuntu 22.04

I am trying to install CUDA 11.7 on Ubuntu 22.04.4 LTS. Based on the official documentation, kernel 5.15 is supported for Ubuntu 22.04. However, when I tried installing cuda, the installer throws the ...
28 votes
5 answers
149k views

Determining cause of Linux kernel panic

I'm running an Ubuntu 12.04 derivative (amd64) and I've been having really strange issues recently. Out of the blue, seemingly, X will freeze completely for a while (1-3 minutes?) and then the system ...
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1 answer
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Why don't devtmpfs populate /dev/pts?

Linux automatically populates a devtmpfs with the right devices and directory structure. This provides an almost complete tree for /dev, but the pts devices are notably missing. For the pts devices, ...
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Why is the "psci-cpuidle" cpuidle driver not used?

On my Raspberry Pi 5, I noticed that /sys/devices/system/cpu/cpuidle/current_driver contained none. So I got the latest kernel sources from here and enabled CONFIG_ARM_PSCI_CPUIDLE in menuconfig. ...
1 vote
1 answer
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error: need to load kernel first

I tried to download Tails on my computer, however, I couldn't do it because in grub there were 2 errors: error:/live/vmlinuz has invalid signature error: you need to load the kernel first Can anyone ...
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How to use the L4 Microkernel with a FreeBSD userland

I'm trying to understand how to use the L4 Microkernel with a FreeBSD userland. I've asked the same to a L4 developer,but he told me that he does not know FreeBSD,so I'm here to ask the same question. ...
1 vote
1 answer
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Debian 12.5 kernel fails to install

Just tried to upgrade to the new Debian Bookworm point release 12.5 But... Building module: Cleaning build area... env NV_VERBOSE=1 make -j4 modules KERNEL_UNAME=6.1.0-18-amd64............................
1 vote
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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-...
13 votes
3 answers
18k views

What exactly happens when I enable net.ipv4.ip_forward=1?

Suppose I have this situation where I wrote a program to poison the ARP cache of 2 devices (let's say A and B), both in the local network to successfully able to MITM from device M. The program runs ...
4 votes
2 answers
7k views

How to dump the dmesg AKA Kernel logs to a single .txt file from the kernel boot?

I am trying to understand the SATA Host-Device Communication and for that I have put a lot of debug messages in the kernel driver code. Now messages are in such a huge amount that I am not able to see ...
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1 answer
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'Operation not permitted' when using modprobe/insmod

I'm trying to install a driver module for a dedicated PCIe board. I'm using the same OS and kernel versions stated in the datasheet but am getting the Operation not permitted error when adding the ...
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1 answer
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Documentation of /sys/block/*/device/type

Where is documentation of /sys/block/*/device/type ? I need information about this file . cat /sys/block/*/device/type 0 0 5 what is this numbers meaning ?
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Sporadic zombie and D state processes on server

I'm writing to seek your expert advice regarding a critical issue affecting my ThinkSystem SR630 V2 server running AlmaLinux 8.9 (kernel 4.18.0-513.9.1.el8_9.x86_64). It hosts two virtual machines on ...
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1 answer
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Mount JFFS2 FS in openwrt

I'm trying to mount 1[MB] of flash as JFFS2 FS in openwrt environment, using 128[MB] NAND flash (4 bit ECC). I'm using the following sequence - flash_eraseall -j dev/mtd6 mount -t jffs2 -o noatime /...
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1 answer
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Error! Your kernel headers for kernel 5.8.0-rc3-microsoft-standard cannot be found while trying to install usb_network_gate on WSL2

I'm trying to install usb network gate on ubuntu 20.04 on WSL2 with this kernel version installed on : root@DESKTOP-N9UN2H3:~/Desktop# uname -a Linux DESKTOP-N9UN2H3 5.8.0-rc3-microsoft-standard #2 ...
1 vote
0 answers
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How to write a program to trigger memory direct reclaim?

First of all, I would like to kindly ask for your assistance in teaching me how to write a program that can trigger direct memory reclamation. I wrote a program that utilizes mmap to allocate memory ...
3 votes
2 answers
2k views

Booting to an encrypted Debian install, which has /boot on LVM-on-LUKS

I have a setup with a grub2 bootloader, and the rest of the system on an encrypted partition (LVM-on-LUKS). I have two OSes installed inside of the LUKS container, Kali Sana and Debian 8, as well as a ...
6 votes
1 answer
8k views

How to compile a third party driver into the kernel?

I am using Linux Mint 17.2 on Toshiba c640. As my LAN driver is no more functional, I am using a USB to LAN converter which was provided with some driver installation files. Every time i want to use ...
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1 answer
8k views

How to find hugepage size on system?

I am getting following two different result. which one i should consider for Hugepage? [root@server ~]# getconf PAGESIZE 4096 [root@server ~]# grep -i hugepagesize /proc/meminfo Hugepagesize: ...
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1 answer
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kernel: OF: overlay: WARNING: memory leak will occur if overlay removed

How can I find the cause of these errors? journalctl -p 3 -b Dec 12 15:19:22 raspberrypi kernel: OF: overlay: WARNING: memory leak will occur if overlay removed, property: /soc/i2c@7e804000/status Dec ...
1 vote
1 answer
138 views

What does qlen 1000 mean for a noqueue qdisc

ip addr show output from within a Kubernetes pod root@customer-fd99fb7dc-82hrr:/app# ip -c addr 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 ...
1 vote
0 answers
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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 ...
4 votes
1 answer
3k views

Where are Kernel global variables stored?

I am currently writing a Linux kernel module. I am aware that in case of userspace programs, uninitialized global variables (exported to other modules using EXPORT_SYMBOL) are stored in BSS segment ...
0 votes
1 answer
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ESP and GRUB instalation

The aim is to install Debian using debootstrap. First I want to install all system on a small 32GB flash disk. And concepts of GPT partition tables and GRUB is quite clear: There is a table of ...
2 votes
1 answer
6k views

How can I use Ubuntu 22.04 on a Samsung Galaxy Book 2 ( NP750XED )?

I installed Ubuntu 22.04 on my Samsung Galaxy Book 2 (NP750XED) by following the official instructions and it works perfectly until I turn the computer off. After boot, when reaching the login prompt, ...
1 vote
1 answer
2k views

linux bpftool not found in linux-tools-common for kernel 4.19.232

I am trying to check if bpf is properly installed in my linux kernel. It's enabled in the kernel as shown: jakew@desktop:~$ cat config | grep BPF CONFIG_CGROUP_BPF=y CONFIG_BPF=y CONFIG_BPF_SYSCALL=y ...
0 votes
1 answer
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CentOS 7.9 not reporting full version number after recompiling kernel

I needed to enable SCSI support in CentOS 7.9 so I followed the instructions here: https://wiki.centos.org/HowTos(2f)I_need_the_Kernel_Source.html to add SCSI support and recompile, which worked as ...
12 votes
2 answers
4k views

Benefiting of sched_autogroup_enabled on the desktop

I am running a 2.6.37 kernel with sched_autogroup_enabled set to 1. I am not certain that I am seeing the benefits of this patch since: I am launching my applications from the desktop; applications ...
1 vote
1 answer
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What is header-data split and why it's needed for TCP_ZEROCOPY_RECEIVE page alignment?

I'm currently investigating about TCP_ZEROCOPY_RECEIVE and I read that it requires header-data split support of NIC. As far as I understand, this feature is to DMA the header (IP, TCP headers) and ...

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