Questions tagged [kernel-parameters]
The kernel-parameters tag has no usage guidance.
121
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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 .....
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2
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51
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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 ...
- 101
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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 ...
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144
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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 ...
- 75
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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"...
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2
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262
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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 ...
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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
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- 335
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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 ...
- 115
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294
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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....
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146
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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 ...
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150
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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 ...
- 11
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85
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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 ...
- 194
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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 ...
- 133
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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 ...
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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 ...
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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 ...
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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 ...
- 2,432
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272
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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 ...
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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: ...
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241
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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 ...
- 521
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483
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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 ...
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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 ...
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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
...
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652
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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,...
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151
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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 ...
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557
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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 ...
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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 ...
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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 ...
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357
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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
$ ...
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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 ...
- 6,324
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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? ...
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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 ...
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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 ...
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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 ...
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521
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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....
- 1,125
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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=...
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675
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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 ...
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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.
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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 ...
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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.
...
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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 ...
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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 ...
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188
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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 ...
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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 ...
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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, ...
- 916
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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 ...
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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?
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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 ...
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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) ...
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System setting to stop WiFi from dropping connection?
My WiFi connection is frequently dropping. Are there any system settings to help with the problem?
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