Kernel Postinstall Script

Overview

This script is executed after installing a new kernel to perform the necessary steps for setting up the initramfs and UEFI boot entries.

Functionality

• Create initramfs with dracut for the installed kernel
• Generate UEFI executable files for the kernel and rescue mode
• Register UEFI executable files as boot entries with efibootmgr

Prerequisites

• dracut must be installed and executable (/usr/bin/dracut)
• efibootmgr must be installed
• The kernel must be configured to use an initramfs (INITRD ≠ 'No')

Execution Conditions

• The script will exit if:
  • No kernel version is passed as a parameter
  • The kernel does not require an initramfs (INITRD = 'No')
  • DEB_MAINT_PARAMS is set and the first parameter is not "configure"

Files and Directories

• /boot: Root directory for creating initramfs and UEFI files
• /boot/efi/EFI/Linux: Target directory for UEFI executable files
• /lib/modules/<Kernel-Version>: Directory for kernel module files

Target Environment

• No Boot Manager: This script is explicitly designed for systems that do not use a boot manager (e.g., GRUB, Syslinux)
• Direct UEFI Boot Configuration: The script directly configures UEFI boot entries to load the kernel and rescue mode

Notes

• The script does not sign the executables for secureboot.
• Ensure all required packages (especially dracut and efibootmgr) are installed and up-to-date.
• Using this script in combination with a boot manager may lead to unexpected behavior. In such cases, prefer boot manager-specific configuration mechanisms.
• This script is designed for use in Debian-based systems but can be ported to other distributions with minor adjustments.

Kernel Postremoval Script

Overview

This script is executed after removing a kernel package to perform the necessary cleanup steps for the initramfs and UEFI boot entries.

Functionality

• Remove the initramfs for the specified kernel version
• Unregister the UEFI executable as a boot entry for the kernel and rescue mode
• Delete the UEFI executable files for the kernel and rescue mode

Files and Directories

• /boot: Root directory for initramfs files (default)
• /boot/efi/EFI/Linux: Directory for UEFI executable files (default)
• initrd.img-<Kernel-Version>: Initramfs file to be removed
• linux-<Kernel-Version>.efi and linux-<Kernel-Version>-rescue.efi: UEFI executable files to be removed

Target Environment

• Post-Removal Cleanup: This script is designed to clean up after a kernel package removal.
• Kernel Package Management: This script is intended for use with kernel package management systems (e.g., Debian's dpkg).

Notes

• This script assumes the UEFI boot entries were created by the corresponding Postinst script.
• This script is designed for use in Debian-based systems but can be adapted for other distributions with minor adjustments.