Questions tagged [kernel-parameters]
The kernel-parameters tag has no usage guidance.
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2answers
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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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0answers
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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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0answers
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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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0answers
28 views
Kernel parameter about max threads not being applied
I have manually edited /etc/sysctl.conf and added this line
kernel.threads-max=70000
However despite the fact that
# cat /etc/sysctl.conf | grep thread
kernel.threads-max=70000
what I see is that
...
0
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0answers
34 views
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 ...
2
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1answer
86 views
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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2answers
92 views
Setting Kernel parameters when grub.cfg is on another distro
My setup is:
-Windows 10 on a M.2 SSD
-Ubuntu 18.04 on a normal ssd (sdb)
-Arch Linux on sdb as well but on different partitions
I first installed ubuntu with grub and later added arch linux ...
0
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1answer
57 views
how to turn off tcp timestamps?
I tried to turn off the tcp timestamp but it didn't work.
The step i performed are the following:
$ sysctl -w net.ipv4.tcp_timestamps=0
$ sysctl -p
$ sysctl net.ipv4.tcp_timestamps (=> to be sure ...
-1
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1answer
1k views
How to disable retpoline?
I need to disable retpoline for a use case. I tried adding noretpoline to the boot parameter but it doesn't seem to work.
The output after adding noretpoline param:
$ cat /sys/devices/system/cpu/...
2
votes
1answer
157 views
Can no_console_suspend be set in runtime?
Is it possible to change this value in runtime without rebooting? I don't always have this problem, when I suspend right now I'm getting a failure and
Suspending console(s) (use no_console_suspend ...
4
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1answer
362 views
lsmod 'used by' shows -1 while CONFIG_MODULE_UNLOAD=y
In this post there is some explanation about why does lsmod show -2 in 'used by' column. The idea is that the kernel config option CONFIG_MODULE_UNLOAD was not set.
But what if lsmod shows -1 only ...
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2answers
82 views
Is Linux kernel parameters separated by space (0x20) or NUL (0x0)?
I thought it was NUL. But today when I wrote a script, I found that it was space. Is it configurable? Or just my memory wrong?
1
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1answer
201 views
How to specify multiple schedulers on the kernel boot command line?
We have systems with both spinning mechanical disks, and NVME storage. We want to reduce the CPU overhead for IO by taking any IO scheduler out of the way. We want to specify this on the Linux boot ...
0
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1answer
138 views
How to add VM kernel parameters in Qubes OS 4.0 ?
How to add sysrq_always_enabled and audit=0 kernel parameters to an AppVM in QubesOS 4.0 ?
Current /proc/cmdline inside the VM is:
[user@dev01-w-s-f-fdr28 ~]$ cat /proc/cmdline
root=/dev/mapper/...
1
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1answer
370 views
How to ensure SysRq is always enabled regardless of the kernel.sysrq setting?
Some Linux distributions have kernel.sysrq=16 which means only Sysrq+s (sync) is allowed. As an example: Fedora (25 and 28) has it set as such in /usr/lib/sysctl.d/50-default.conf
I had to create a ...
0
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1answer
46 views
Understanding workload sharing of readwrite in fio
I am exploring fio tools with different options.
I want to share the read and write workload, so supplied below jobfile to fio.
[read-4K-write-64K]
blocksize=4K,64K,
rw=readwrite
rwmixread=50
size=...
2
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1answer
384 views
Linux Modify/Add Kernel Command Line from InitramFS “UserSpace”
I am developing an embedded Linux device. I have successfully created an InitramFS CPIO archive that runs quickly after boot. Now, I want to change the initial kernel command line to include "quiet" ...
1
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1answer
437 views
How does FIO benchmark set IOdepth?
NOTE: My question stems from this other U&L Q - What exactly is iodepth in fio?
I want to know how internally FIO sets I/O depth. I.e., one of the parameters we submit to FIO when we run it is "...
1
vote
1answer
142 views
Kernel flags for exact architecture [closed]
I am using linux-libre-4.17.3. I want to switch off all unnecescary stuff like 'Amateur radio', Xen, Hyper-V, Wifi drivers that I am not using and so on...
I think web search does not satisfy me. ...
3
votes
1answer
456 views
Kernel parameters are not changed permanently for RHEL7
Trying to permanently change some vm kernel parameters, I created /etc/sysctl.d/01-custom.conf config file as it described in Red Hat knowledgebase article. Here is its content:
# cat /etc/sysctl.d/...
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0answers
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Weird kernel.shmax value [duplicate]
I've noticed that kernel.shmmax value is set to oddly huge number on my RHEL 7 system.
# sysctl kernel.shmmax
kernel.shmmax = 18446744073692774399
Is it OK to have such a huge number set?
How can ...
0
votes
1answer
25 views
Boot kernel parameter to run an executable at the end of booting, if found
Is there such a feature? The executable would be run if found after the usual boot time mounting. Preferably standard Unix filesystem path; for example, /root/autorun.sh, not (hd0,0)/root/autorun.sh. ...
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0answers
258 views
Can't change kernel.printk value
I want to set kernel.printk value to 5 4 1 1 for disable logging on booting but when I try
sysctl -w kernel.printk="5 4 1 1"
I get error:
sysctl: setting key "kernel.printk": Invalid argument
...
4
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1answer
547 views
Difference between modprobe and sysctl -w in terms of setting system parameters?
We know that sysctl command can change kernel parameters with :
# sysctl -w kernel.domainname="example.com"
or by directly editing the file in /proc/sys directory. And for persistent changes, the ...
1
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1answer
578 views
ACPI kernel parameter options for HP ProLiant DL380 G5
Heavily related to a question on the sister site (https://serverfault.com/questions/874943/debian-9-black-screen-during-install), I have recently picked up an HP ProLiant DL380 G5 and attempted to ...
1
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1answer
662 views
How to increase atomic DMA coherent pool?
I recently attempted to compile a device driver (Xilinx XAPP1052) on Fedora Workstation 20. It gave me the following error.
ERROR: 256 KiB atomic DMA coherent pool is too small!
Please ...
0
votes
1answer
379 views
Why does the fs.inode-max kernel tunable not exist on version 2.6 of the Linux kernel?
The following output (from a Vagrant VM running CentOS 6.6) mostly speaks for itself:
[root@localhost ~]# echo 131072 > /proc/sys/fs/inode-max
-bash: /proc/sys/fs/inode-max: No such file or ...
2
votes
1answer
452 views
What does the Linux kernel do with unknown kernel parameters?
Supposedly I passed the kernel a parameter that it doesn't understand, for example blabla or eat=cake, what would the kernel do with these unknown parameters, the traditional case would be passing any ...
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0answers
487 views
Compile Kernel 3.10.107 for Ubuntu 16.04 LTS
Is there a good way to compile and use kernel 3.10.107 on Ubuntu 16:04 LTS?
My main reason is that I have development/server machine where I want to add additional USB device what have drivers only ...
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2answers
2k views
can't mount on /proc/cmdline
I followed the this instructions in order to change the kernel boot args after boot:
https://wiki.archlinux.org/index.php/kernel_parameters#Hijacking_cmdline
I created /root/cmdline , but when ...
2
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0answers
538 views
How to get video mode given by hwinfo when it doesn't work? And how to set login resolution?
I tried to follow the suggestion at this previous post:
Use sudo hwinfo --framebuffer as described, choose a video mode you would like to see during boot in console, then add the option vga=nnn to ...
1
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1answer
872 views
Default kernel parameters on new network namespaces
What are the default kernel parameters, when creating a new network namespace? Is there a way to override them upon creation?
I think they are inherited by the parent process. An example using ...
1
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1answer
3k views
Kernel module for net.bridge.bridge-nf-call-iptables
This is on the Linux OS.
I see that on some machines the net.bridge.bridge-nf-call-iptables variable doesn't exist until I modprobe the br_netfilter filter. I also see that there are some machines ...
3
votes
1answer
2k views
LUKS password not being requested by dmcrypt / encrypt hook at boot
At boot I see:
:: running hook [encrypt]
A password is required to access the volume:
Command requires device and mapped name as arguments
Command requires device and mapped name as arguments
...
3
votes
1answer
2k views
LUKS discard/TRIM: conflicting kernel command line options
I'm confused between the various ways that LUKS/dmcrypt/cryptsetup discard /TRIM operations can be enabled via the Linux kernel command line.
The dracut manpage:
rd.luks.allow-discards
Allow ...
4
votes
2answers
2k views
Select graphics card for console output
I have an HP DL380G9 server with two discreet nvidia graphics card installed running RHEL 6 with Kernel 2.6.32-573. Both cards have the same chipset (NV117) but different models. K620 (Slot 5 address ...
3
votes
1answer
6k views
Kernel 4.8.7 failure on cpufreq - CentOS 7
After upgrading my CentOS 7 kernel from 3.10.0 to 4.8.7, while rebooting the system I will get the following lines:
[ 0.641455] cpufreq: cpufreq_online: Failed to initialize policy for cpu: 0 (-19)...
5
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0answers
3k views
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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votes
1answer
13k views
Cannot compile kernel: error, kernel does not support PIC mode
I have troubles recompiling my Kernel. Downloading the source package, decompress it and running
fakeroot make-kpkg kernel_image
leads me to the error
[...]
CHK include/...
3
votes
2answers
1k views
reboot with one-time kernel parameters
Is there a possibility to pass a (set of additional) kernel boot parameters to be applied at the next (re)boot, and only at that boot?
I know that i could just interrupt grub and manually pass the ...
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0answers
207 views
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?
0
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1answer
407 views
How can I configure the Linux kernel to ignore passed in parameters?
I have the kernel parameters for our embedded device set during kernel build time, but these can be overridden by passing other parameters from the bootloader.
Is there a way to build a kernel that ...
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1answer
2k views
Kernel parameter quiet versus loglevel=4 and debug versus loglevel=7
Besides the possibility of userspace applications that care which one you use reading /proc/cmdline, what is the difference between using the kernel parameter quiet, versus loglevel=4, and the ...
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2answers
530 views
What are methods for recovering a Linux Kernel config?
I'm currently trying to rebuild the kernel for a proprietary device. In order to do this I will need to produce a kernel config for the device. While I could likely do this through trial and error, ...
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0answers
145 views
How to prevent access to HDD during Live-CD operation?
I want to safely disable the harddrive / harddisc (HDD) of my computer with boot parameters.
I can not physically unplug it.
BIOS / UEFI does not provide me an option to disable it.
Can I use the ...
2
votes
1answer
6k views
Kernel parameters “console” and “earlycon” refer to old hardware?
I first found this by investigating parameters for earlycon but found that the options for console look almost identical. Both are present below and were taken from this source:
From documentation ...
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1answer
849 views
How to configure device mapper name of encrypted root partition with Grub2?
I would like to have my encrypted root partition mapped to the device mapper name system, i.e. it should eventually appear under /dev/mapper/system. My operating system is Fedora 24 Workstation Linux ...
2
votes
1answer
1k views
How to let kernel not run the printk with KERN_DEBUG
I noticed that kernel has different console levels for the printk.
I also noticed this post [1].
I understand that we can change the /proc/sys/kernel/printk to change the printk level for the ...
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0answers
176 views
How should the `crypto` kernel parameter be passed?
I've encrypted a root drive using a cipher with this format:
<cipher>-<chainmode>-<ivmode>:<ivopt>.
Let's call this [CIPHER] for short.
To boot from this device, certain ...
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2answers
11k views
View current kernel parameters?
I saw in my syslog kernel.perf_event_max_sample_rate get changed.
I was wondering if I could write a quick script to log this variable every few minutes.
Currently it is:
sysctl -a | grep kernel....
