MIME-Version: 1.0
From: Hokus Pokus <pawel.polawski@gmail.com>
Date: Fri, 27 May 2022 19:16:41 +0200
Message-ID: <CAE49SAg7-9R+tD7XjJXn3RArjTNaE9cc-DcRyU1kqULdim1Kcg@mail.gmail.com>
Subject: Alpine linux kernel modules loading
To: ~alpine/users@lists.alpinelinux.org
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Hi all,

I have a question related to kernel modules loading
on Alpine Linux. The system I am working with is
Alpine Extended 3.15.4 with kernel 5.15.32-0-lts.

So far I found that kernel modules are loaded via:

1) Modules passed as kernel arguments (cat /proc/cmdline)
modules=sd-mod,usb-storage,ext4
Above is processed by the initramfs init (product of mkinitfs)
and modprobe is called for every module on the argument list.

2) mdev hotplug modules load:
/etc/mdev.conf:
$MODALIAS=.* root:root 0660 @modprobe -q -b "$MODALIAS"
This is for hotplug devices and modules for them.

3) OpenRC calling /etc/init.d/modules which process:
- /lib/modules-load.d/*.conf
- /etc/modules
- /etc/modules-load.d/*.conf
- /run/modules-load.d/*.conf
Then modprobe is called for valid entries in above files.

4) OpenRC calling /etc/init.d/hwdrivers
This one search /sys for modalias files and tries to load
matching modules using modprobe ("cold" hardware modules).

If I miss something and there is yet another level of
modules loading?

Explanation:
I am creating Alpine initramfs.cpio using mkinitfs.
The plan is to build a custom initramfs to play with.
My initramfs will not switch_root to HDD at the end
but will live in RAM only. To achieve this I want
to replace original init script created by mkinitfs with my own.
I have /sys, /dev and /proc setup ready and most of the script done.
Only remaining part is kernel modules loading.

The naive approach would be to just create list of modules
that needs to be loaded and call modprobe for
all of them. This would work as long as hardware will not change.
I want to make it more intelligent and merge OpenRC
logic (/etc/init.d/modules, /etc/init.d/hwdrivers).
I am wondering if this will be enough to make it working
or OpenRC is doing something more, not presented in those scripts.

Best regards,
Pawel

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<div dir=3D"ltr"><div>Hi all,</div><div><br></div><div>I have a question re=
lated to kernel modules loading</div><div>on Alpine Linux. The system I am =
working with is</div><div>Alpine Extended 3.15.4 with kernel 5.15.32-0-lts.=
<br></div><div><br></div><div>So far I found that kernel modules are loaded=
 via:</div><div><br></div><div>1) Modules passed as kernel arguments (cat /=
proc/cmdline)<br></div><div>modules=3Dsd-mod,usb-storage,ext4</div><div>Abo=
ve is processed by the initramfs init (product of mkinitfs)</div><div>and m=
odprobe is called for every module on the argument list.</div><div><br></di=
v><div>2) mdev hotplug modules load:</div><div>/etc/mdev.conf:</div><div>$M=
ODALIAS=3D.*	root:root	0660	@modprobe -q -b &quot;$MODALIAS&quot;</div><div=
>This is for hotplug devices and modules for them.<br></div><div><br></div>=
<div>3) OpenRC calling /etc/init.d/modules which process:</div><div>- /lib/=
modules-load.d/*.conf</div><div>- /etc/modules</div><div>- /etc/modules-loa=
d.d/*.conf</div><div>- /run/modules-load.d/*.conf</div><div>Then modprobe i=
s called for valid entries in above files.</div><div><br></div><div>4) Open=
RC calling /etc/init.d/hwdrivers</div><div>This one search /sys for modalia=
s files and tries to load</div><div>matching modules using modprobe (&quot;=
cold&quot; hardware modules).</div><div><br></div><div>If I miss something =
and there is yet another level of</div><div>modules loading?</div><div><br>=
</div><div>Explanation:<br></div><div>I am creating Alpine initramfs.cpio u=
sing mkinitfs.</div><div>The plan is to build a custom initramfs to play wi=
th.</div><div>My initramfs will not switch_root to HDD at the end</div><div=
>but will live in RAM only. To achieve this I want</div><div>to replace ori=
ginal init script created by mkinitfs with my own.</div><div>I have /sys, /=
dev and /proc setup ready and most of the script done.<br></div><div>Only r=
emaining part is kernel modules loading.</div><div><br></div><div>The naive=
 approach would be to just create list of modules</div><div>that needs to b=
e loaded and call modprobe for</div><div>all of them. This would work as lo=
ng as hardware will not change.</div><div>I want to make it more intelligen=
t and merge OpenRC</div><div>logic (/etc/init.d/modules, /etc/init.d/hwdriv=
ers).</div><div>I am wondering if this will be enough to make it working</d=
iv><div>or OpenRC is doing something more, not presented in those scripts.<=
br></div><br><div>Best regards,</div><div>Pawel<br></div></div>

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