Custom Gentoo Linux kernel

Upgrading kernel

Fetch firmware distfiles to install missing firmware files after reboot (when network can be unavailable):

BASH

emerge -f linux-firmware intel-microcode

Install new kernel version and update config:

BASH

USE="symlink" emerge -av gentoo-sources
cd /usr/src
cp -a linux-OLD/.config linux/
make oldconfig

Configure setup options in /etc/genkernel.conf. Most important are:

INSTALL – install kernel to /boot directory, equivalent to:
BASH
```
genkernel --install kernel
```
SAVE_CONFIG – store kernel config in /etc/kernels/,
LVM, MDADM, MDADM_CONFIG – add initramfs support for booting from LVM/mdadm device , equivalent to one of:
BASH
```
genkernel --lvm initramfs
genkernel --mdadm --mdadm-config=/etc/mdadm.conf initramfs
```
FIRMWARE, ALLFIRMWARE, FIRMWARE_DIR – include all firmware files from /lib/firmware in initramfs. This assumes:
- sys-kernel/linux-firmware is installed with +savedconfig and /etc/portage/savedconfig/sys-kernel/linux-firmware- contains list of selected firmware files,
- sys-firmware/intel-microcode is installed with +hostonly. Equivalent to:
  BASH
```
genkernel --all-firmware initramfs
```
MODULEREBUILD – re-emerge packages containing kernel modules after new kernel has been built, equivalent to:
BASH
```
emerge @module-rebuild
```
COMPRESS_INITRD_TYPE – compression algorithm has to be enabled in kernel, e.g. xz setting requires RD_XZ kernel option,
TMPDIR – /var/tmp/portage/genkernel

then run:

BASH

genkernel all

Reboot. Check for missing firmware files and install as necessary:

BASH

dmesg | grep firmware | grep failure

Option names and configuration symbols are based on Linux Kernel v6.12.

Sending files over interface using e.g. blueman:

Control flow Enforcement Technology, used when +cet USE flag is enabled for build toolchain:

###. TODO: merge wiki kernel install