Questions tagged [kernel-parameters]

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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
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2 answers
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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 ...
ABeginner's user avatar
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1 answer
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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
2 votes
1 answer
144 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
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1 answer
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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
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2 votes
2 answers
262 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
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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
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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
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294 views

Recommended kernel parameters for zswap

There are a lot of proposals for this in the zram context, but not for zswap. What would be acceptable kernel parameters? vm.swappiness=100 (or even higher?) vm.vfs_cache_pressure=500 (really?) vm....
mav's user avatar
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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
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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
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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
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0 answers
89 views

Celeron J4105, screen flickering after reboot

I have a Dell Wyse 5070, with a Celeron J4105 CPU. I have installed a Debian Bullseye distribution, kernel 5.10, and screen flickers after reboot. There is no error message from the kernel. On cold ...
Bertrand125's user avatar
7 votes
2 answers
3k 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
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
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Grub menu not recognizing ctrl button on boot

I need to install a graphics driver for Debian to boot properly on my mid-2011 iMac. To do that, I first need to boot without the graphics card, so I can be logged in. I found that I need to press e ...
Globe's user avatar
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114 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
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1 answer
272 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
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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
241 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
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1 answer
483 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
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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
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1 answer
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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
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1 vote
2 answers
652 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
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0 answers
151 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
557 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
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284 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
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2 votes
1 answer
1k 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
357 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
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1 vote
0 answers
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slub_min_objects : How comes 0 can stand as a valid / default value?

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
  • 6,324
2 votes
1 answer
190 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
0 answers
506 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
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1 vote
0 answers
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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
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2 votes
1 answer
785 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
  • 206
0 votes
1 answer
521 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
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2 votes
2 answers
1k 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
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5 votes
4 answers
675 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
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1 vote
1 answer
308 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
3k 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
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273 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
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0 votes
1 answer
354 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
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0 votes
1 answer
1k views

acpi_os_name and acpi_osi semantics

I'm experiencing strange behaviour with hibernation on my laptop, and want to pretend that I'm running a recent version of Windows to see if this helps things. Microsoft's How to Identify the Windows ...
Tom Hale's user avatar
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0 votes
1 answer
188 views

kernel boot logging causes delay

I see a very strange behaviour on some (not all) of my Linux machines. I am running Arch Linux with kernel 5.8.8-arch1-1 If I start the machine without grub loglevel parameter (or apply any from ...
df8oe's user avatar
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2 votes
2 answers
5k views

What is setting the the console_loglevel at boot?

I recently installed Arch Linux on a System76 Lemur Pro laptop. The installation seemed to complete successfully, but the console_loglevel is set to the very high value of 15. The following command ...
Trevor's user avatar
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1 vote
0 answers
1k views

How do I tell the linux kernel that I don't have IPMI?

I'm trying to clean up known or bogus error messages that shows up in the log when I boot my Debian server, in order to more clearly see actual errors. Now it's come to this: Base address is zero, ...
pipe's user avatar
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0 votes
1 answer
891 views

Using "acpi=off" in a virtual machine

Does using the kernel command-line option acpi=off in a virtual machine (i.e VirtualBox 5.2) make sense when the host OS has been booted with ACPI on ? I mean for debuging purposes if someone wants to ...
Parsa Mousavi's user avatar
2 votes
0 answers
111 views

I forgot to set CONFIG_LOCALVERSION_AUTO=y

I compiled Linus's latest git tree and I forgot to set CONFIG_LOCALVERSION_AUTO=y. How can I make the system behave the same way as if I had set that option before booting into it?
B K Karthik's user avatar
0 votes
0 answers
194 views

Hardware compatibility issues

I have recently switched to Linux and no matter what operating system I use or configurations I edit I can not seem to get Linux to work properly on my desktop pc where on my laptop Ubuntu worked ...
Cyber's user avatar
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2 votes
2 answers
2k views

How do I enable a configuration in a Kernel?

As the title says, I am trying to enable KASAN in my Manjaro distribution for a project, but I have no idea how to. The documentation here (https://www.kernel.org/doc/html/v4.14/dev-tools/kasan.html) ...
winterlyrock's user avatar
0 votes
1 answer
579 views

System setting to stop WiFi from dropping connection?

My WiFi connection is frequently dropping. Are there any system settings to help with the problem?
Matthew Cline's user avatar