Arch Linux

CarbonChauvinist

Member

Registered: 2012-06-16

Posts: 413

Website

Kernel Command Line vs. Modprobe.d

If I've set module options in my boot loader's kernel command line and I've also set options for the same module in /etc/modprobe.d/ how is the application of those options handled? Does one supercede the other? What if I have conflicting options in the modprobe.d folder and the kernel command line?

For instance assume this is my boot loader's entry:

 ghost  ~  cat /boot/loader/entries/arch-lvm.conf 
title Arch Linux (LVM)
linux /vmlinuz-linux
initrd /intel-ucode.img
initrd /initramfs-linux.img
options cryptdevice=UUID=145628bb-0138-4b8b-bc94-2d041c756539:lvm:allow-discards root=/dev/mapper/lvmvg-root i915.enable_rc6=1 i915.disable_power_well=1 i915.enable_psr=-1 quiet rw

But, if I have the following in /etc/modprobe.d/i915.conf:

ghost  ~  cat /etc/modprobe.d/i915.conf 
options enable_rc6=1 disable_power_well=0 enable_psr=1 enable_fbc=1 enable_psr=1

Which option will be applied for disable_power_well? Will it be the '0' from modprobe.d or the '1' from arch-lvm.conf?

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"the wind-blown way, wanna win? don't play"

Head_on_a_Stick

Member

From: The Wirral

Registered: 2014-02-20

Posts: 9,003

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Re: Kernel Command Line vs. Modprobe.d

Which option will be applied for disable_power_well? Will it be the '0' from modprobe.d or the '1' from arch-lvm.conf?

Why not just try it and see what happens?

FWIW, I think that the kernel option will be applied first and then be superseded by the modprobe.d option when the filesystem is loaded.

If I'm right you owe me a biscuit 

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Jin, Jîyan, Azadî

x33a

Forum Fellow

Registered: 2009-08-15

Posts: 4,587

Re: Kernel Command Line vs. Modprobe.d

Mod note: Moving thread to "Kernel & Hardware".

seth

Member

From: Won't reply 2 private help req

Registered: 2012-09-03

Posts: 76,349

Re: Kernel Command Line vs. Modprobe.d

systool -vm i915

The precedence isn't documented, so the behavior is unspecified. Last I know is that the kernel cmdline overrode the modprode.d options, but the NOT the install key.

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