[Arm-dev] kernel modules vs builtin

Jim Perrin jperrin at centos.org
Mon Apr 25 13:46:28 UTC 2016

Sorry for the delayed response, I've been traveling for the last couple

On 04/22/2016 05:15 AM, Sakar Arora wrote:
> Hi Jim

> Should we use built in kernel support for devices/file systems (like
> USB, XFS, SquashFS etc.) needed for CentOS installation, or go with the
> modular approach of having the modules placed in the initrd.img?

You should not need to change filesystem bits like XFS or SquashFS. That
already works out of the box on other gear and shouldn't require

> Are all the modules in initrd.img copied to the
> initramfs-4.2.0-0.27.el7.1.aarch64.img, created at the completion of
> CentOS installation?

The initramfs is created when the kernel package is installed, as part
of the post-installation scripts. The installer initramfs is a bit
custom, and generated via the lorax command run. The short answer is
'no, not all modules are copied'.

> Right now I am facing an issue, where, if I go with the modular
> approach, USB device driver does not get probed correctly and am not
> able to install CentOS from USB.

This sounds a bit like a driver issue without knowing the specifics. USB
already has a fair bit of support compiled in so that it does autodetect
devices. This is fairly critical for keyboard/mouse support as well as
USB storage. If it's not working, I'd suspect something in how the
chipset is communicating to the kernel.

> On the other hand, if I compile the USB driver built in to the kernel,
> USB device driver gets probed fine and I am able to proceed with CentOS
> installation.

Is the module missing from the installer, or present and not working as

Jim Perrin
The CentOS Project | http://www.centos.org
twitter: @BitIntegrity | GPG Key: FA09AD77

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