compile_kernel_preemptrt

#!/bin/bash
# Script for compiling a Linux kernel with the PREEMPT_RT real-time patch with a simple graphical interface
# Tobit Flatscher - github.com/2b-t (2022)
#
# Usage:
# - '$ ./compile_kernel_preemptrt' and follow through the installation with a graphic user interface
# - Select a PREEMPT_RT version at https://mirrors.edge.kernel.org/pub/linux/kernel/projects/rt/"
#   and run this script with '$ sudo ./compile_kernel_preemptrt 5.10.78-rt55'


function install_kernel_interactive() {
  declare desc="Install the kernel with a graphic user menu and let the user decide which version to choose"
  {
    info_msg "Installing dependencies..."
    sudo apt-get install -y dialog
    install_dependencies
    success_msg "Dependencies installed successfully!"
  } || {
    warning_msg "Warning: Could not install dependencies. Installation might fail!"
  }

  local PREEMPTRT_FULL_VERSION=$(select_preemptrt)
  local KERNEL_FULL_VERSION=$(extract_kernel_full_version "${PREEMPTRT_FULL_VERSION}")

  info_msg "Downloading and extracting kernel and patch..."
  local KERNEL_FILE=$(download_and_extract_kernel "${KERNEL_FULL_VERSION}") 
  local PREEMPTRT_FILE=$(download_and_extract_preemptrt "${PREEMPTRT_FULL_VERSION}")
  success_msg "Kernel and patch downloaded and extracted successfully!"

  info_msg "Applying patch to kernel..."
  apply_patch_to_kernel "${PREEMPTRT_FILE}" "${KERNEL_FILE}"
  generate_new_kernel_configuration
  success_msg "Patch applied successfully!"
  info_msg "Forcing unsigned kernel..."
  unsign_kernel_configuration

  local INSTALLATION_MODE=$(select_installation_mode)
  if [ "${INSTALLATION_MODE}" == "Debian" ]
    then
      generate_preemptrt_kernel_debian_package
      IS_INSTALL_NOW=$(select_install_now)
      if [ "${IS_INSTALL_NOW}" -eq 0 ]
        then
          install_preemptrt_kernel_debian_package "${PREEMPTRT_FULL_VERSION}"
          success_msg "Done: Installation with Debian package completed!"
      else 
        warning_msg "Done: Debian package generated successfully but installation skipped!"
      fi
  else
    install_preemptrt_kernel_directly
    success_msg "Done: Classic installation complete!"
  fi
}

function install_kernel_noninteractive() {
  declare desc="Install the PREEMPT_RT kernel by patching a kernel and installing it as a Debian package from a given command-line argument (e.g. 5.10.78-rt55) without interactive choices"
  {
    info_msg "Installing dependencies..."
    install_dependencies
    success_msg "Dependencies installed successfully!"
  } || {
    warning_msg "Warning: Could not install dependencies. Installation might fail!"
  }

  local PREEMPTRT_FULL_VERSION=$1
  local KERNEL_FULL_VERSION=$(extract_kernel_full_version "${PREEMPTRT_FULL_VERSION}")

  local KERNEL_FILE=$(download_and_extract_kernel "${KERNEL_FULL_VERSION}")
  local PREEMPTRT_FILE=$(download_and_extract_preemptrt "${PREEMPTRT_FULL_VERSION}")
  apply_patch_to_kernel "${PREEMPTRT_FILE}" "${KERNEL_FILE}"
  generate_new_kernel_configuration
  unsign_kernel_configuration
  generate_preemptrt_kernel_debian_package
  install_preemptrt_kernel_debian_package "${PREEMPTRT_FULL_VERSION}"
  success_msg "Done: Installation with Debian package completed!"
}


function main() {
  declare desc="Install the kernel either in an interactive or non-interactive way depending if an input argument is given"
  local CURRENT_PATH=$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd)
  local LIB_OUTPUT="${CURRENT_PATH}/lib_output.sh"
  local LIB_INSTALL_DEBIAN="${CURRENT_PATH}/lib_compile_kernel.sh"
  source "${LIB_OUTPUT}"
  source "${LIB_INSTALL_DEBIAN}"

  set -e # Exit immediately in case of failure
  if [ "$#" -eq 0 ]; then
    install_kernel_interactive
  elif [ "$#" -eq 1 ] && [ "${EUID}" -eq 0 ]; then
    install_kernel_noninteractive $@
  else
    error_msg "Error: Could not run installation script!"
    info_msg "Either launch it as: "
    info_msg " - '$ ./compile_kernel_preemptrt'"
    info_msg " - '$ sudo ./compile_kernel_preemptrt 5.10.78-rt55'"
    info_msg "For the available PREEMPT_RT versions see: "
    info_msg "see https://mirrors.edge.kernel.org/pub/linux/kernel/projects/rt/"
    exit 1
  fi
  exit 0
}

main $@