6 Kernel Development FAQ

6.1 Common Questions and Solutions

Here are some solutions for common questions.

6.1.1 How do I use my own Linux kernel .config file?

Refer to the “Changing the Configuration” section for information.

6.1.2 How do I create configuration fragments?

A: Refer to the “Creating Configuration Fragments” section for information.

6.1.3 How do I use my own Linux kernel sources?

Refer to the “Working With Your Own Sources” section for information.

6.1.4 How do I install/not-install the kernel image on the rootfs?

The kernel image (e.g. vmlinuz) is provided by the kernel-image package. Image recipes depend on kernel-base. To specify whether or not the kernel image is installed in the generated root filesystem, override RDEPENDS_${KERNEL_PACKAGE_NAME}-base to include or not include “kernel-image”. See the “Using .bbappend Files in Your Layer” section in the Yocto Project Development Tasks Manual for information on how to use an append file to override metadata.

6.1.5 How do I install a specific kernel module?

Linux kernel modules are packaged individually. To ensure a specific kernel module is included in an image, include it in the appropriate machine RRECOMMENDS variable. These other variables are useful for installing specific modules: - MACHINE_ESSENTIAL_EXTRA_RDEPENDS - MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS - MACHINE_EXTRA_RDEPENDS - MACHINE_EXTRA_RRECOMMENDS

For example, set the following in the qemux86.conf file to include the ab123 kernel modules with images built for the qemux86 machine:

MACHINE_EXTRA_RRECOMMENDS += "kernel-module-ab123"

For more information, see the “Incorporating Out-of-Tree Modules” section.

6.1.6 How do I change the Linux kernel command line?

The Linux kernel command line is typically specified in the machine config using the APPEND variable. For example, you can add some helpful debug information doing the following:

APPEND += "printk.time=y initcall_debug debug"