Understanding conf file in /etc/modprobe.d/

I am trying to understand how to use conf file in /etc/modprobe.d/. For instance on my system I define:

$ cat /etc/modprobe.d/nouveau.conf
# debug nouveau
options nouveau debug="PGRAPH=debug"

After a shutdown followed by a fresh start here is what I see:

$ dmesg | grep nouveau
[ 1.495465] [drm:nouveau_drm_init [nouveau]] Loading Nouveau with parameters:
[ 1.495490] [drm:nouveau_drm_init [nouveau]] ... tv_disable : 0
[ 1.495515] [drm:nouveau_drm_init [nouveau]] ... ignorelid : 0
[ 1.495539] [drm:nouveau_drm_init [nouveau]] ... duallink : 1
[ 1.495563] [drm:nouveau_drm_init [nouveau]] ... nofbaccel : 0
[ 1.495587] [drm:nouveau_drm_init [nouveau]] ... config : (null)
[ 1.495611] [drm:nouveau_drm_init [nouveau]] ... debug : PFIFO=debug

Which is confirmed by:

$ sudo cat /sys/module/nouveau/parameters/debug
PFIFO=debug

So it looks like upon startup the nouveau module is reading from another location the debug option (since PGRAPH != PFIFO). Where is this alternate file stored ? How do I find out which one is used ?

1 Answer

nouveau is starting from initramfs.

To change load options for this kind of modules you need to run

sudo update-initramfs -u

to get the setting applied.