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.
1,235
questions with no upvoted or accepted answers
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NVMe PCIe disk power cycling
I want to test an 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 radiation (e.g., ...
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0
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What network connections are not seen by netstat/lsof/ss?
Network monitoring tools ss, lsof -i, netstat -ltupw and similar have limitations like namespace and thus they don't show the whole machine connections. (for namespace created with ip we can see other ...
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1
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Linux 3.x fails assigning PCI BAR memory
I got an IBM x3850 type 8864 machine, I can successfully boot using a 2.6.32 kernel but when I try to use a 3.10 kernel or newer the kernel fails to initialize all PCI slots (I can fix this (manually),...
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Why are block sizes limited by page size in Linux?
In many (all?) file systems that Linux uses, including ext2/3/4, the maximum block size is the page size of the architecture Linux is running on, ie. 4KiB on x86. Why is there this limit? Might this ...
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How to read the output of the show-memory-usage SysRq?
I couldn’t find any (recent) documentation on reading the output of the show-memory-usage SysRq (Alt+SysRq+m). So what can one learn from looking at it?
Here is an example output form my box (Kernel ...
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6
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0
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171
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Kernel config for keyboard special LEDs
I'm building a 4.9 linux kernel (which is working great) for my T460s. The F1 key has a led that shows if sound is muted. I can't get this LED to work even when enabling all kinds of LED-relevant ...
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6
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1
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What does "make install" do in the Makefile that comes with the kernel?
I'm trying to identify what does make install do with the kernel and what does the actual "install" of the kernel once it's been compiled means.
The problem is I can't really identify the target (...
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5
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NFS Cannot allocate memory
The other night I was trying to restart NFS services but then I received the following error messages:
kernel: [81818.428785] nfsd: unable to allocate nfsd_file_hashtbl
rpc.nfsd[15567]: error starting ...
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5
votes
1
answer
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How does one disable an option enabled by default in Kconfig?
Let's say I have an option:
config SETTING_WITH_DEFAULT
bool "Some setting which defaults to y"
default y
I want to make an option which would deselect this default:
config ...
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5
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0
answers
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How does linux decide the load address and entry point when execve an ELF?
When linux execve() an ELF, it will mmap that ELF into the process's memory space and start to run code from the entry point. But how does the kernel decide the load address and entry point of the ELF?...
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How to check if If i2c-hid and hid-rmi are not used for touchpad?
I'm seeing the following warning in dmesg:
[ 2.631179] psmouse serio2: synaptics: Your touchpad (PNP: SYN1218 PNP0f13) says it can support a different bus. If i2c-hid and hid-rmi are not used, you ...
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Kernel compiling - Error during sync of the configuration
I am trying to compile the 4.19 kernel on my Linux Mint machine. I copied my current config (which is from 4.15), opened make menuconfig in order to append a local version string, saved it and then ...
- 703
5
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CPU high load native_queued_spin_lock
I'm using Debian 9(stretch edition) kernel 4.9., hp dl385 g7 server with 32 cpu cores. NIC queues are tied to processor cores. Server is shaping traffic (iproute2 and htb discipline + skbinfo + ipset +...
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Can't run any snap using linux 4.12 : snap-confine has elevated permissions and is not confined but should be
I am using Ubuntu 17.04 with linux kernel 4.12.2 which I installed using the software ukuu (Ubuntu Update Kernel Utility).
Every time I try to run a snap in my system when I am using this linux ...
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5
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1
answer
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Getting big endian linux build to boot on ARM with u-boot
I’m trying to make a big endian build of a linux distribution for ARM. Since I’m on Gentoo, cross-compiling couldn’t be easier. I’ve already built it all, but then got stuck with getting it/the kernel ...
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5
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Difference between syscalls and raw_syscalls events?
AFAIK different linux tracing tools gather information from /sys/kernel/debug/tracing/events directory where different events are logged. Can anyone explain the difference between "syscalls" event and ...
5
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0
answers
437
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Grub.conf vs sysctl.conf
Both files are being used to pass parameters to the kernel. so what exacly is the difference between the two? What is the purpose of each file?
- 255
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357
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Kernel config diffs - better way to maintain
I maintain one Linux distro (LEAF) with multiple kernel targets, so it needs to have multiple kernel configs (one reference config + usual patch files for other targets). But this adds headache on ...
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5
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1
answer
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DisplayPort and Intel HD cause GPU hangs
My system has problems with the displayport connection. This is indicated by several problems that, at the first glance, do not have anything in common. The reason why I claim DP for being the cause, ...
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5
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2
answers
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Problem when trying to cross-compile an ethernet driver on an old Linux kernel
I'm currently trying to cross-compile a network driver against an old Linux kernel, in version 2.6.27.7 but the compilation fails and prints:
make[1]: entering directory « /home/johann/Desktop/linux-...
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5
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0
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When would I use FBDEV vs DRM vs DSS?
I'm interested in developing a graphics driver. I see that Linux supports three methods for writing graphics to the display device
FBDEV
DRM
DSS2
When would I use one versus the other?
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1
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How are Linux kernel bugs being tracked?
What an hour of Googling bring out that mainstream Linux kernel bugs are being logged in two distinct systems:
Mailing list
This is the Linux kernel development discussion and bug reporting
...
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4
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1
answer
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Compiling external kernel module fails on Debian bookworm due to missing resolve_btfids
I am new to linux and I am trying to compile an external kernel module on a Debian bookworm virtualization (UTM).
Makefile
obj-m += hello_world.o
PWD := $(CURDIR)
all:
make -C /lib/modules/`...
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4
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0
answers
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How does anti-cheat work and how is it distributed on Steam Games?
According to Levvvel's list of kernel-level anti-cheat games, many modern games use kernel-level anti cheat. One provider of kernel-level anti-cheat is Epic with Easy Anti-Cheat and one game using ...
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4
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0
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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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1
answer
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How to debug Linux kernel with JTAG + GDB?
I've successfully established a JTAG connection and serial port connection to my development board. I've followed the below diagram (with a little bit of difference).
my GDB_client is on my Linux host ...
4
votes
0
answers
508
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Linux kernel cannot execute any binary (error -12)
Problem: Memory Allocation Problem
my platform:
SOC = STM32H743 (ARMv7E-M | Cortex-M7)
Board = Waveshare CoreH7XXI
Linux Kernel = 5.8.10 (stable 2020-09-17)
initial defconfig file = stm32_defconfig
...
4
votes
0
answers
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QEMU kernel for raspberry pi 3 with networking and virtio support
I used the QEMU(qemu-system-aarch64 -M raspi3) for emulating the Raspberry pi3 with the kernel from the working image.
Everything was working but there was no networking.
qemu-system-aarch64 \
-...
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4
votes
1
answer
447
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Kernel Panic not showing up?
I'm writing a kernel module and I was hoping to get the beautiful Kernel Panic screen with all the details when I call panic(), but my machine just freezes without displaying anything.
I know kpanic ...
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4
votes
0
answers
369
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udev rule not worknig as expected with PROGRAM key
My system is Debian Buster with Kernel 4.19. I have a simple udev rule as below that was working fine with Debian Jessie. Now same rule seems to be not working in newer distribution.
KERNEL=="sd[a-z]...
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Is there any tool to generate kernel .config file?
I watched a clip on customizing kernel, rebuilding, installing, etc. where the gentleman suggested to use an existing .config file with make menuconfig or make xconfig. I wanted to use one that comes ...
user358527
4
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0
answers
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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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4
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0
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732
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How to additional public keys to .secondary_trusted_keys?
I am trying to add additional keys to .secondary_trusted_keys. Documentation says, to do so the additional keys has to be signed by a key which is already a resident in either .builtin_trusted_keys or ...
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4
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5
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Kernel cannot find init in initramfs image
I'm trying to get my embedded system to run an initramfs. Right now 'init' in this initramfs does nothing but echo a message to test if it is being ran.
My init script:
#!/bin/sh
echo "HELLO ...
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4
votes
0
answers
761
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Time measurment in Linux kernel: how are clock_gettime, gettimeofday and getrusage related?
I am trying to understand how time is measured by the Linux kernel. I tried to go through the kernel code, but I miss the big picture to understand the code that I'm reading, even if this article ...
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4
votes
1
answer
4k
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Controlling USB-C Power Delivery on a HP ProBook G5 laptop
Question: I want to look at parameters under /sys/class/typec, but on my laptop, this doesn't show up. When I load the typec module manually, the directory appears but it is empty. After loading tcpm ...
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4
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0
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Which Linux kernels include a particular bug fix?
How do I know which Linux kernels have merged a particular bug fix?
For example, as mentioned in this question:
Kernel Bug 198357 - iwlwifi: failed to remove key (1, ff:ff:ff:ff:ff:ff) from hardware ...
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4
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0
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What is the modern way to develop a Linux auditing kernel module?
I'm new to Linux Kernel development, and I am now assigned a task to develop a Linux kernel module, which can monitor the network, filesystem, USB and serial ports.
I am aware of the things like ...
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4
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1
answer
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How can I detect whether an "NMI watchdog: BUG: soft lockup" is a hardware or a software issue?
Soft Lockup
dmesg reports in my laptop, since quite some time now, NMI watchdog: BUG: soft lockup every time I try to use updatedb or firefox. Samples of what is reported posted at https://github.com/...
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1
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Finding which specific Python process was killed by Linux OOM killer
I'm trying to figure out which specific Python process or executable was killed by the Linux OOM killer.
In /var/log/messages I get this:
Aug 18 03:19:11 169 kernel: [ 7747] 0 7748 3226957 ...
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4
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0
answers
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Prevent a plus sign from being appended to Linux build
The kernel build system like to append + to the kernel's local version string whenever it detects that the source tree is version controlled with Git. I can prevent this annoying modification to ...
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0
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Limit on number of virtual interfaces in linux?
I am running some automated tests with docker containers, and this includes creating a lot of veth interfaces (about 2 per container, ~1000 containers).
Whenever I do this, the system shuts down. ...
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1
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How do I extract vmlinux from an ARM image?
I am trying to extract vmlinux from Ubuntu's netboot kernel used in the armhf architecture. The script extract-vmlinux returns
extract-vmlinux: Cannot find vmlinux.
It even fails when I try to use ...
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0
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Dell XPS 13 9350 wifi dying with Broadcom BCM4350 and 4.8 kernel
Launchpad report: for all those with the same problem, please subscribe to this report I opened in Launchpad so that it can gain some traction.
I've been using Ubuntu 16.04 with kernel 4.7 for some ...
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1
answer
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Are devices with kernels below 3.6 vulnerable to CVE-2016-5696?
Today I was reading about the potential impact of CVE-2016-5696 in Android phones running Linux 3.6+ and though my phone has 3.4 I checked the value of net.ipv4.tcp_challenge_ack_limit and it is also ...
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4
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1
answer
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using cpu.cfs_quota_us and cpu.cfs_period_us to limit CPU usage
There are 32 cores in a system (2 cpus each 16 cores) and I want to
limit a user to use only 4 cores (100% usage for that 4 cores). There
are two kernel parameter for that according to the manuals:
...
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4
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2
answers
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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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0
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Print kernel memory layout
Userland memory layout can be inspected by looking into /proc/self/maps.
I am wondering if there is a similar facility allowing to inspect runtime kernel memory layout?
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Centos 7 boot up with custom kernel problem
I have installed centos 7 on virtualbox machine which has kernel-3.10.0-123.20.1.el7.x86_64. I am trying to build Linux kernel from kernel sources. I downloaded the kernel source files from: http://...
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1
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Corrupt LVM metadata header after kernel update
I'm running Debian Wheezy (Linux wheezy3.2.0-4-amd64 #1 SMP Debian 3.2.63-2+deb7u1 x86_64 GNU/Linux) as an encrypted LVM with hardware raid 1 (Adaptec 6405E) on a supermicro server.
I was encounting ...
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