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Undefine CONFIG_BLK_CGROUP macro while building linux kernel image

I am wanted to build a custom kernel image in which macro CONFIG_BLK_CGROUP is not defined. After researching a little bit I found we can do such configurations in .config file. To be more precise I ...
mSatyam's user avatar
  • 111
1 vote
1 answer
109 views

Understanding the “memmap” Linux parameter

I'm trying to understand the “memmap” parameter from the Linux kernel (see The kernel’s command-line parameters), in particular, the following options: memmap=nn[KMG]$ss[KMG] [KNL,ACPI] Mark ...
Franks's user avatar
  • 143
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0 answers
13 views

Configure hashsize of nf_conntrack_xxx on kernel 5.x

In my system running kernel 4.x, it load 3 modules which are nf_conntrack, nf_conntrack_ipv4 and nf_conntrack_ipv6. Only nf_conntrack_ipv4 is modprobe-ed with hashsize param which is greater than ...
dustin2022's user avatar
0 votes
1 answer
55 views

Boot a kernel of debian installer with expert mode

I want to reinstall my VPS with the debian's official repository, instead of with the image provided by the VPS operator(I don't trust the VPS operator). On original system I installed debian-...
Leon's user avatar
  • 163
0 votes
0 answers
98 views

Setting user passwords via kernel parameter

What is the correct syntax to use these bits of information from systemd manual: systemd-sysusers(8) will look for the credentials passwd.hashed-password., passwd.plaintext-password. and passwd.shell....
gcb's user avatar
  • 428
1 vote
1 answer
332 views

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 ...
Grant Curell's user avatar
0 votes
1 answer
70 views

Difference between sysctl options to set system parameters

I see on the web two different commands to load sysctl custom parameters: sysctl --system sysctl -p Is there any difference between the two commands? I know the second one I posted can take the path ...
matteo-g's user avatar
  • 103
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1 answer
204 views

Is there an official way to set kernel parameters in /boot/boot.scr in Debian?

I have installed Debian 12 on my Orange Pi Zero using a custom u-boot image. I notice that Debian has a file called /root/boot.scr which is rebuilt after apt upgrades. I had previously modified this ...
user111395's user avatar
1 vote
1 answer
1k views

What's the difference between the kernel boot parameters nohz_full and isolcpus=nohz

When isolating CPU cores for jitter-sensitive processes it is common to use both boot parameters nohz_full and isolcpus (I know the latter is deprecated in favor of cpusets, but it's still around). ...
Manuel Bernhardt's user avatar
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1 answer
73 views

“binutils”/Kernel 6.5.X - “Invalid –compress-debug-sections option: `zstd’”

I'm trying to build a driver for a USB to HDMI adapter... Bus 001 Device 010: ID 534d:6021 MacroSilicon VGA Display Adapter NOTE: "lsusb" output. ... but this error is occurring... Fatal ...
Eduardo Lucio's user avatar
1 vote
1 answer
1k views

What is the console setting for kernel early_printk in Linux?

I am working on an embedded Linux (kernel-5.10.24), and I enabled the early_printk in kernel configuration to help my debugging kernel. Normally, the kernel command line has set console=ttyS0,115200 .....
wangt13's user avatar
  • 443
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2 answers
101 views

Why can't keyboards be used in customized linux?

I am customizing a Linux system using a Linux kernel of 6.4.0. After booting, why is the keyboard not working? # 1. The disk is externally connected through a USB interface. If I enter the Linux live ...
just a student's user avatar
0 votes
1 answer
233 views

How do disable MMC Command Queue Engine

What is the kernel parameter to disable the Command Queue Engine driver? I am reading through mmc.c MMC_DEV_ATTR(cmdq_en, "%d\n", card->ext_csd.cmdq_en); /* * Enable Command Queue if ...
Bret Joseph's user avatar
3 votes
1 answer
646 views

How to disable/enable bounce-buffers in IOMMU?

I am trying to figure out how to disable bounce buffers used in IOMMU when the hardware IOMMU is used. To give more context, when IOMMU_DEFAULT_DMA_STRICT is set in the kernel it enables strict IOTLB ...
sammy17's user avatar
  • 95
3 votes
1 answer
555 views

GRUB hangs itself with 64bit Memtest86+ BadRAM pattern?

When I add the "badram" pattern that 64bit Memtest86+ v6.10/v6.20 gave me, GRUB 2 hangs completely on boot. Q: Why is the badram pattern address different from the "Error Address"...
nyov's user avatar
  • 193
2 votes
2 answers
982 views

Linux kernel difference between protected and reserved memory? (memmap parameter)

The Linux kernel takes a memmap parameter *) to manually designate memory regions for different use-cases. Q: What is the difference between reserved memory (memmap=nn[KMG]$ss[KMG]) and protected ...
nyov's user avatar
  • 193
0 votes
0 answers
511 views

How do we input multiple kernel parameter for the same module?

Lets say I want to put command line args for a kernel module. If the module is some_module.ko. In modprobe I would go, options some_module option1=value option2=value In kernel command line I would go ...
Bret Joseph's user avatar
0 votes
1 answer
54 views

Which Kernel version should I download to recompile my kernel with lock stats enabled

I'm trying to use the CLI tool perf, however it requires the CONFIG_LOCKDEP and CONFIG_LOCK_STAT enabled in the Kernel code. I understand that to enable these flags, I need to download the source code ...
someone12321's user avatar
1 vote
0 answers
284 views

In the middle of "Too many files open" mess

I am in the middle of "file limit" mess and I am not sure what to do. I am sure restarting the system will help for a while. However, could someone point me in the right direction for tools ...
oldhomemovie's user avatar
  • 1,707
4 votes
1 answer
2k views

Set affinity of a process using TASKSET or sched_setaffinity() to a processor core isolated using CPUSET

First, let me give a background of what I am trying to achieve. I know how to isolate a particular CPU using boot param (isolcpu and nohz_full; the housekeeping subsystem setup). But as per my ...
Abhishek Ghosh's user avatar
1 vote
0 answers
258 views

Recompiling a Kernel module from source

Good night, I am trying to recompile a kernel module from its source (in case you are wondering, it is the b43 driver module) on Debian 11. I've ran into a problem, which is that I want to specify ...
as43z's user avatar
  • 11
0 votes
1 answer
143 views

kernel ignores append init=/bin/bash

qemu-system-x86_64 -m 2G -accel kvm -kernel kernel6.1 -append "init=/bin/bash" -initrd myinitrd.gz Supposed to run bash as init, but kernel still prints: [ 1.400577] Run /init as init ...
exebook's user avatar
  • 202
7 votes
2 answers
5k views

Difference between net.ipv4.conf.all.forwarding and net.ipv4.ip_forward

According to https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt conf/all/* is special, changes the settings for all interfaces forwarding - BOOLEAN Enable IP forwarding on this ...
Ahmed Gasanov's user avatar
4 votes
2 answers
1k views

Disable webcam at boot time, by appending a boot parameter

I have an internal webcam on my Dell laptop. I don't see it listed with lspci, but it works. I am using a self-compiled kernel, and here are the options I have enabled: # zcat /proc/config.gz | grep -...
Martin Vegter's user avatar
1 vote
0 answers
3k views

Is there an `ibt=off` linux command-line parameter?

I use Arch Linux - I recently did a full system upgrade and I am now experiencing a hang up on boot that seems to relate to the nvidia module. This Arch Wiki page (under Installation) describes some ...
Time4Tea's user avatar
  • 2,405
1 vote
0 answers
219 views

Kernel data structure that shows which CPUs are partitioned (isolated) using tuned?

This is for Red Hat Linux 7.9, kernel 3.10.0-1160.71.1 . I would like to know what kernel data structure can be used to show which CPUs it thinks are isolated using tuned. This means I've isolated ...
Mike S's user avatar
  • 2,592
1 vote
1 answer
494 views

Compiling kernel with specified parameter

You can easily change kernel parameters with sysctl and then make it persistent with /etc/sysctl.d but is there a fast way to change default kernel parameters like default vm.swappiness = 60 at the ...
EdiD's user avatar
  • 342
0 votes
1 answer
2k views

get rid of rebooting messages and watchdog

Broadcast message from username@Desktop (Sun 1919-08-10 11:45:14 CST): The system is going to reboot NOW! [756.345947] watchdog: watchdog0: watchdog did not stop! [756.472889] watchdog: watchdog0: ...
Firestar-Reimu's user avatar
2 votes
0 answers
344 views

How to blacklist some scsi devices via a kernel parameter?

I need to tell kernel to completely ignore some SCSI devices (eg. from vendor 'PURE'). I see libata.force=x.yy:disable can be used for individual SATA devices, but I need something equivalent for SCSI ...
Jiri B's user avatar
  • 531
1 vote
1 answer
752 views

Do subsequent arguments override previous from linux kernel command line, or vice versa?

This was prompted by another question elsewhere, which after digging into briefly a quick online search ("linux kernel command line override priority" and some variations) turned up ...
goldilocks's user avatar
  • 88.1k
0 votes
1 answer
2k views

CentOS 7 - Isolated cores are not isolated in practice

I have a pair of CentOS 7 servers (7.9.2009) with 8 physical CPUs each. Out of those, I'm trying to isolate cores 4-8 (so 3-7 as the OS sees them). I added the tag isolcpus=3-7 to /etc/default/grub ...
PGEL's user avatar
  • 157
3 votes
1 answer
2k views

pcie_bus_perf : Understanding the capping of MRRS

Quoting the linux kernel documentation for boot parameters : pcie_bus_perf : Set device MPS to the largest allowable MPS based on its parent bus. Also set MRRS (Max Read Request Size) to the largest ...
MC68020's user avatar
  • 8,239
1 vote
2 answers
823 views

linux-zen VS cfs-zen-tweaks

I'm using Arch on a very old computer with Chrome and it crashes pretty often, plus the CPU consumption is very high. I read that using cfs-zen-tweaks could improve the responsiveness. Which is better,...
Kureteiyu's user avatar
  • 155
1 vote
0 answers
279 views

How can I pass a parameter to a module that is not built-in to the kernel using GRUB2?

If I choose to have a module built-in (Y), I can choose "e" to edit the boot entries on GRUB2 and modify the kernel command line to include "module.variable=whatever" and it works ...
user3161924's user avatar
3 votes
1 answer
829 views

Why jiffies/HZ does not match uptime?

System uptime is stored in /proc/uptime. As you know, the Linux kernel has a jiffies variable which increments by each timer interrupt specified by the HZ parameter. I got the value ofHZ by the ...
javadr's user avatar
  • 131
0 votes
0 answers
402 views

How to find a kernel source code for ARM cortext-A55?

I want to know how to find a proper Linux kernel source code for using ARM cortext-A55. I got a kernel source code from kernel.org. But don't know how to "Config" my kernel to support ...
CH J's user avatar
  • 1
2 votes
2 answers
2k views

Disable GTT on amdgpu?

How can I disable GTT on amdgpu? According to https://www.kernel.org/doc/html/v4.20/gpu/amdgpu.html, adding amdgpu.gttsize=0 should work but that has no effect. The reason why I am asking is, that my ...
InvisibleShadowGhost's user avatar
1 vote
0 answers
668 views

Why would Linux kernel drop the isolcpus parameter?

I'm trying to pass isolcpus=1-4 to the kernel command line, Linux version 5.10.42 LTS. My boot manager is EFISTUB/efibootmgr. I'm booting OK but the parameter is simply not there when checking with $ ...
haelix's user avatar
  • 592
1 vote
0 answers
85 views

slub_min_objects : How comes 0 can stand as a valid / default value / rationale?

In the comments of the source code (mm/slub.c) of my linux_5.4 kernel, I can read : In order to reach satisfactory performance we must ensure that a minimum number of objects is in one slab. Otherwise ...
MC68020's user avatar
  • 8,239
2 votes
1 answer
319 views

Where to get offline documentation/descriptions of individual sysctl kernel tunable parameters?

The NOTES section of $ man 5 sysctl.conf states: The description of individual parameters can be found in the kernel documentation. But is there a way for me to find this kernel documentation offline? ...
Jethro Cao's user avatar
3 votes
2 answers
879 views

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 ...
arminb's user avatar
  • 171
1 vote
0 answers
181 views

Does kernel boot support serial redirection at very high speeds?

I have a UART that is displayed in a Linux boot log as: AMDI0020:01: ttyS5 at MMIO 0xfedca000 (irq = 4, base_baud = 3000000) is a 16550A I want to enable Linux kernel boot log to this UART port. To ...
kostr22's user avatar
  • 216
2 votes
1 answer
1k views

Is it possible to set serial speed for an early kernel boot log to a MMIO UART?

I have a UART that is displayed in a Linux boot log as: AMDI0020:01: ttyS5 at MMIO 0xfedca000 (irq = 4, base_baud = 3000000) is a 16550A I want to enable Linux kernel boot log to this UART port. To ...
kostr22's user avatar
  • 216
0 votes
1 answer
686 views

How do you find the physical offset for a file in BTRFS?

I have a swap file in BTRFS for which I need the resume_offset for the kernel command line. How do I calculate its CORRECT physical offset ? filefrag does not work. btrfs_map_physical.c does not work....
ng.newbie's user avatar
  • 1,235
3 votes
2 answers
2k views

badram kernel parameter not working?

I have bad ram which is soldered on so I can't replace it. I have run memtest86+ and got the output in badram format. I added this to the current kernel with: sudo grubby --args=badram=...
eggbert's user avatar
  • 173
5 votes
4 answers
721 views

Finetuning kernel for high swap environment

I own an 8GB RAM Dell XPS13 9343; the amount of RAM is the biggest pain of this computer, it's soldered on mainboard. Despite the CPU supporting more RAM, even resoldering bigger ones with firmware ...
nusch's user avatar
  • 61
1 vote
1 answer
398 views

Is there a difference between Kernel parameters and the bootloader parameters?

I often see editing of grub2 parameters to change kernel parameters (i.e. loglevel, quiet, intremap, etc...), but I think there are also grub2 parameters and I'm lost to what they actually are. ...
holeInAce's user avatar
3 votes
1 answer
4k views

spectre_v2=retpoline and performance

https://stackoverflow.com/questions/48089426/what-is-a-retpoline-and-how-does-it-work https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html?highlight=kernel%20parameters Control ...
ron's user avatar
  • 7,239
0 votes
0 answers
335 views

When there's no grub, how to change gpu kernal parameters?

I currently use dual AMD R9 gpus. However, I recently was forced to upgrade motherboards and to the next version of my linux distro. My old motherboard was BIOS based, and my new one is UEFI based. ...
lilHar's user avatar
  • 125
0 votes
1 answer
447 views

How to reverse engineer kernel configs for a prebuilt kernel?

I am trying to build a kernel module for a commercial gadget which runs Linux 4.9.x. The kernel module that I build crashes the kernel. I believe this is because of wrong kernel configurations. I have ...
johcn's user avatar
  • 1