Questions tagged [kernel-parameters]

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Why does grub kernel parameter slub_debug=P crash the system with some software?

I've observed that when passing slub_debug=P (together with FZ) as a kernel parameter to grub, KDE Plasma will crash when I close the electron-based note taking software Obsidian. I don't understand ...
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Custom compiled kernel not showing updated changes

I have been following the How Tos/Custom_Kernel (I Need to Build a Custom Kernel) document at the CentOS Wiki to compile my kernel. I modified the kernel in ~/rpmbuild/BUILD/kernel-4.18.0-305.3.1....
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Are iodepth and iodepth_batch the same in fio?

Wanted to know the difference between iodepth parameter and iodepth_batch parameter in fio. Here is what is mentioned in fio read the docs : iodepth=int Number of I/O units to keep in flight against ...
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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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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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Kernel Parameter to Boot LiveUSB with Specific UserID like username

First off, I apologize if this question is incorrectly worded, in the wrong place, or otherwise not completely in accordance with community standards. If that is the case, in my defense, I have been ...
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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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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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Make root partition not mountable when system is hibernating

Mounting a the root partition in another os when the "owner" is hibernating is dangerous. After resume the file system gets corrupted. As of kernel documentation: BIG FAT WARNING ***********...
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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 ...
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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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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....
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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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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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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, ...
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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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MTRR (Memory Type Range Register) in Debian 10 dmesg messages

[Sun Mar 1 07:51:40 2020] MTRR default type: uncachable [Sun Mar 1 07:51:40 2020] MTRR fixed ranges enabled: [Sun Mar 1 07:51:40 2020] MTRR variable ranges enabled: [Sun Mar 1 07:51:40 2020] ...
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Use ISO9660 USB for booting

I'm trying to boot from a USB drive that has an ISO file dd'd onto it with dd if=file.iso of=/dev/sdb. The ISO file was created using grub2-mkrescue, and it boots about half the time if I specify root=...
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Network kernel command line (ip=) doesn't set the ip or route in Ubuntu 18 on Firecracker

I'm trying to launch a Firecracker VM with Ubuntu and set up networking. If I launch it regularly (taken from this repo): ./firectl --kernel=vmlinux --root-drive=image.ext4 --firecracker-binary=./...
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Controlling the page cache usage

The unfortunate situation that we're in right now is that historically, we've been over-provisioning RAM to our on-prem VMs and we're starting to run up to the limits of actual usage with midday ...
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Looking for dynamic kernel parameters from sysctl -a command

as title states, I'm looking to select both dynamic and fixed variables from sysctl -a command. Some parameters get changed every reboot? and I would like to have list of both dynamic and fixed. As I ...
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How to set sysctl using kernel command line parameter?

Is it possible to set Linux kernel sysctl settings (those usually set in /etc/sysctl.d) using kernel command line (those visible in /proc/cmdline)? (Using grub config file /etc/default/grub variable ...
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grub2-mkconfig not using /etc/default/grub?

I'm trying to add a kernel option "xxx" by adding it to the existing GRUB_CMDLINE_LINUX="xxxx crashkernel=auto rhgb quiet" line in /etc/default/grub, but after doing so, when I run grub2-mkconfig –...
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Can I use kernel parameter printk.time during boot to disable showing timestamps?

I am trying to use the kernel parameter printk.time in order to prevent showing timestamps in kernel messages logged in dmesg. According to this, it's possible to set printk.time=0 to disable the ...
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GRUB: escape acpi_osi="Windows 2015" in GRUB_CMDLINE_LINUX

How do I escape the string: acpi_osi="Windows 2015" To keep the space and quotes in GRUB's GRUB_CMDLINE_LINUX? [Alternate search term: acpi_os_name=]
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How to change Kernel Base address when compiling Linux?

I am working on RedPitaya FPGA board and want to use Asymmetric MultiProcessing on it. CPU0 will be running Linux and CPU1 will be running Baremetal or freeRTOS. For that I need to change the Kernel ...
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Compiling Linux kernel with all available drivers

I'm compiling the kernel for usage in portable USB stick. Which means it must run on any hardware, not just hardware of the machine where it is being compiled. What should I choose in kernel config ...
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Can I turn kernel params to make the network stack using swap instead of physical memory?

I'm doing a test about high-currency, and I only have a machine with limited memory. My goal is to setup more than 10M TCP connections on this memory limited machine. It seems that the network stack ...
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Addressing USB-Stick by UUID as kernel parameter in grub.cfg

I'm using Arch Linux and setting up an USB-Stick as decryption key for my luks-encrypted root partition (boot is unencrypted). I described it already in this question. Now, the key, that's used for ...
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How to configure embedded linux kernel so that the file system is visible on the host linux

I am using a powerpc, and after building and flashing the linux kernel on the device I can see the file system. But if I try to create a user or make any changes they get erased and resets to default ...
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boot parameters seems not to work with ipxe and daily image

I am trying to auto install debian buster with ipxe, it seems that the boot parameters don't work in the ipxe menu. I always get the language section. So the preseed isn't loaded. Here is the relevant ...
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