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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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Can't load kernel

I'm a Mint user. I was trying to solve a problem, which is that when I suspend my PC I can't resume. I found on stack exchange Ubuntu an answer saying to use "ukuu" in order to upgrade the kernel. ...
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1answer
20 views

Read keyboard inputs in Linux

I am making a Ruby program so I can play different sounds when a key is pressed. Key A will make different sound from key S and so on. I want to get raw inputs rather than using some ruby gems. For ...
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Binary executable file with write permission get READONLY from vim

First I know that use vim to write a binary executable program is not recommended. So, I don't want to talk about its rationality here. I have a binary program, with permission 755(owner is root), so ...
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0answers
692 views

OpenWRT image for OrangePi

I need to build the OpenWRT image for OrangePi PC and|or OrangePi Plus board, preferably with working Ethernet and HDMI. I have studied related resources on the internet, like OpenWRT and linux-sunxi ...
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Need to recompile module ideapad_laptop, how?

I found that ideapad_laptop doesn't have my laptop, causing wifi to not work. I need to edit and recompile the file. The file is here. Now I want to recompile that file and the other files it needs so ...
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14 views

Boot problems on Ubuntu 16.04 (elementary os) with kernel 4.4.0-145

After a recent update on my dual boot hp laptop with secure boot disabled, whenever I switch back to linux (from windows 10) on the default kernel (4.4.0-145) the boot process gets stuck in this loop ...
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24 views

Why can't I debug the kernel running in a virtual machine after inserting a bad device driver (Linux Kernel Module)?

Background: I downloaded kernel version 5.0.3 from kernel.org and then configured it for debugging, compiled it and installed the modules for it in my virtual machine. Then I took the uncompressed ...
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1answer
39 views

unlink/rm target of an open symlink

I've come across an issue where processes that load symlinked .so files crash if I update the .so while the processes are still running. I have long-running processes that load shared libraries (.so)...
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25 views

Realtek RTL8821 Ethernet card not detected by Kali Linux

When installing kali linux an error message appears during the step "Detect network hardware", the message says : "No Ethernet card was detected. if you know the name of the driver needed by your ...
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0answers
17 views

Linux kernel module address randomization

I'm booting the same 16.04 Ubuntu server image (4.4.* kernel) and checking where modules are loaded with cat /sys/modules/[module_name]/sections/.text. After every boot I get different text segment ...
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1answer
59 views

Why is kernel module blacklisting so weak?

There have been several times in the past year or two where I have tried to blacklist Linux kernel modules (either through blacklist.conf or kernel command line parameters), and yet it hasn't worked - ...
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1answer
19 views

How to manually mount the virtual file systems, to copy MTD partitions

Linux version 2.6.26.5, ARM Linux Kernel on embedded device, NAND-based device. I'm at Busybox rescue shell (ash), with restricted command set. How to manually mount the virtual file systems, to copy ...
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1answer
3k views

NVMe PCIe disk power cycling

I want to test a NVMe SSD that is connected to a PCIe slot of my motherboard. The test procedure is a specific algorithm that writes workloads to the SSD, while the SSD is exposed to radiations (e.g. ...
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1answer
8k views

Kernel panic : Kernel offset disabled

I was trying to install the linux-next kernel in my system with the following steps. Copied the existing configuration file from /boot to the root of source directory Updated the .config file with ...
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2answers
307 views

Does the Linux kernel have its own page table?

Different processes have different different page tables for their address spaces. Does the Linux kernel have its own page table? If not, how are the virtual addresses of kernel translated to ...
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1answer
21 views

Does the kernel address region in user page tables need to be updated in an 64 bit system?

In 32 bit systems with more than 896 MB of RAM it is obvious, that the mapping of kernel addresses need to be changed because of kernel virtual addresses and the non-continuous mapping. But how is ...
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1answer
177 views

XFRM_SUB_POLICY config in kerne

When testing strongswan performance, we saw that the performance differed by a lot between an ubuntu server and a centos server, with everything else being the same. We noticed that the ...
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1answer
112 views

How is the page cache mapped in the kernel on 64-bit x86 architectures?

On a modern 64-bit x86 Linux, how is the mapping between virtual and physical pages set up, kernel side? On the user side, you can mmap in pages from the page cache, and this will map 4K pages in ...
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1answer
33 views

How is the Linux git repo related to other distribution git repos (such as Ubuntu)?

I am trying to build a custom version of my Ubuntu kernel, and want to apply a patch that I see on the main Kernel tree. I know that Ubuntu development happens in these repos: git://git.launchpad....
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1answer
360 views

Copy files from VCD without conversion to MPEG

I'm using a Fedora 23-like OS (Korora) and recently I got my hands on an old VCD. Korora recognized it as a "Video CD" all right and Nautilus even gave me an option to play using VLC. But as soon as I ...
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6answers
189k views

Linux: How to find the device driver used for a device?

If my target has one device connected and many drivers for that device loaded, how can I understand what device is using which driver?
2
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1answer
260 views

How does a 64-bit Linux Kernel manage page tables for a 32-bit application in compatibility mode?

At the moment I am reading the book "Understanding the Linux Kernel". There the following is said: For 32-bit architectures with no Physical Address Extension, two paging levels are sufficient. ...
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0answers
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How to view ICMP Redirect Logs

I have read on multiple sources that there is are logs for rejected ICMP redirect messages, one of them being "Understanding Linux Network Internals: Guided Tour to Networking on Linux" By Christian ...
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22 views

How can I implement multiple kernels into bsd/Linux? [on hold]

Like on the lowest level, on multiple cpu machines I want oop code organizing things in the fashion of multidimensional binary trees.
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1answer
461 views

Linux Mint Cinnamon won't boot to GUI, only FreeDOS [closed]

Trying to dual-boot Linux with windows 10. I formatted my flash drive with Rufus, then copied the 18.2 64-bit Linux mint Cinnamon file to the root of the drive. When I try to boot from the drive, it ...
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0answers
22 views

kernel TCP/IP implementation - about accept queue

I'm recently learning the TCP/IP implementation in linux kernel(version 4.4), and got really confused about the accept queue. I know there is a queue in struct inet_connection_sock which is called a ...
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0answers
18 views

I can boot directly from guest kvm?

I install linux as guest on kvm, there is way to boot from that linux when i open my computer? like live usb.
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1answer
48 views

“Forcing” a kernel panic from the terminal on Linux

I'm using Solus 4.0 (in a VM) and trying to make screenshots of "typical" kernel panic output ("BSOD"). The init system in Solus is systemd. I tried the following commands in the terminal without ...
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0answers
35 views

What is led_cdev? And how to use it in Linux kernel (directly)?

I'm trying to debug a kernel panic on an embedded device with no access to serial output. The device has a small notification LED which is supported by a driver in the Linux kernel. So, I thought ...
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2answers
65 views

How to find the names of partitions of a given block device?

Given a block device (e.g, /dev/sda), how to determine the names of its partitions (if any) in a script (i.e. without user interaction)?
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4answers
7k views

NMI received for unknown reason 20 — Do you have a strange power saving mode enabled?

I am using Debian GNU/Linux 7.8 (wheezy). While running my MATLAB program today, I got this message in terminal. Message from syslogd@sas21 at Jul 18 16:40:49 ... kernel:[1747708.091929] Uhhuh. NMI ...
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1answer
875 views

Single system image (clustering) solutions

Are there any Single System Image (clustering) solutions being actively developed? Kerrighed's last version targeted Linux 2.6.30 and the latest OpenSSI seems to target Linux 2.6.14. Perhaps there's ...
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0answers
50 views

overall HIGH CPU utilization, but top is not showing process which is contributing to that spike

Below is the output of a top command, which is showing "57.6%us, 24.0%sy" overall cpu utilization at a particular moment, but there is no process which is contributing to this spike of cpu usage. ...
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ebtable rule to disable packet(other than BPDU) flood/forward on bridge device

The configuration has one bridge device and two ports attached to it. The requirement is to disable flooding or forwarding of any packet from bridge device to other associated ports. How to achieve ...
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1answer
22 views

How large are the “watermark” memory reservations on my system?

swappiness 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. A value of ...
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2answers
553 views

Can anyone recommend some linux kernel related books for beginners? [closed]

I want to know the mechanism of Linux kernel. But I was confused by such a huge number of concepts, structs and functions after the reading of Understanding the Linux kernel. This book details too ...
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1answer
377 views

I want to participate in linux kernel development, where can i find some what is needed to do? [closed]

I want to participate in linux kernel development but i don't have idea what, in technically meaning i can do (i am looking for tasks). I am experienced C programmer, i know some linux kernel, i have ...
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1answer
3k views

Getting kernel source code (ubuntu)

I want to try my hand at writing a linux driver. I am trying to set up my environment. My current kernel: $ uname -r 4.10.0-37-generic I then download the source code: $ apt-get source linux-image-$...
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0answers
46 views

make: *** No targets. Stop. error when trying to build Linux Tree Directory

I just start contributing on Linux Kernel. I am following this guide https://youtu.be/LLBrBBImJt4?t=1052 . Up to that point I did required changes. Run the script to check for the code and it was ...
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1answer
25 views

Where is CONFIG_HZ defined?

I'm in the middle of reading the whole Linux 5.0.7 source code, and I've noticed something strange. I'll refer to linux as the parent directory here, correct me if the community uses some other naming ...
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1answer
2k views

How to debug Linux hang?

We are using beagle bone black based custom board, with kernel version 3.12. We are facing system hang during one of the init script,(Which brings up WiFi) this hang happens after random number of ...
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1answer
18 views

Can I change LIO SCSI Disk Vendor name

I'm using LIO for SAN scsi. The shared disks shown as LIO-ORG at client side. Example; [root@testing ~]# lsblk -S NAME HCTL TYPE VENDOR MODEL REV TRAN sdc 4:0:0:0 disk LIO-...
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1answer
38 views

How to disable TCP checksum validation on Linux?

For some reason, I want to disable TCP checksum validation on my Linux host. Is that possible to disable it?
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24 views

Is there a way to find out which process is setting a Linux kernel parameter to an invalid value at runtime?

I have set the kernel parameter fs.inotify.max_user_instances to 100000000, but it is automatically getting set to 1256 after a while. Is there some way to figure out which process is setting it to ...
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0answers
16 views

Kernel-core fail

I use Fedora 29 (xfce), and today it's starts to break my browsers. Appears to me the message: "unexpected error" "the system encountered a problem and recovered" but, it's been happening even me ...
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0answers
25 views

Is linux mount propagation asynchronous to the mount call?

I have two processes in different mount namespaces. They have a shared directory bind mounted to /mnt/share. The "master" uses MS_SHARED propagation for the mount, while the "slave" uses MS_SLAVE. ...
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2answers
8k views

Kernel compilation error recipe for target 'deb-pkg' failed

I am compiling the latest kernel cloned from Linus's git repository for a challenge. Here are the steps I followed, 1. Installed cross compilation tools sudo apt-get install git build-essential ...
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1answer
90 views

Why does Linux have two data segments, one for user mode and another for kernel mode?

Linux have (in addition to other segments) a user data segment and a kernel data segment. When the CPU is in user mode, Linux loads the segment selector of the user data segment into the DS register. ...
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1answer
2k views

Is iptables string matching still supported?

I was reading the book Linux Firewalls - Attack Detection and Response (by M. Rash, No Starch Press, 1 Ed., Oct. 2007). In one of its chapter it discusses string matching using iptables. I was ...
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1answer
2k views

Issue with Hugepage reservation in linux

I have reserved hugepages for my process using below commands: #echo 64 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages #mkdir -p /mnt/huge && mount -t hugetlbfs nodev /mnt/huge ....