path: root/archiso/mkarchiso

#!/usr/bin/env bash
#
# SPDX-License-Identifier: GPL-3.0-or-later

set -e -u
shopt -s extglob

# Control the environment
umask 0022
export LC_ALL="C.UTF-8"
if [[ -v LANGUAGE ]]; then
    # LC_ALL=C.UTF-8, unlike LC_ALL=C, does not override LANGUAGE.
    # See https://sourceware.org/bugzilla/show_bug.cgi?id=16621 and https://savannah.gnu.org/bugs/?62815
    unset LANGUAGE
fi
[[ -v SOURCE_DATE_EPOCH ]] || printf -v SOURCE_DATE_EPOCH '%(%s)T' -1
export SOURCE_DATE_EPOCH

# Set application name from the script's file name
app_name="${0##*/}"

# Define global variables. All of them will be overwritten later
pkg_list=()
bootstrap_pkg_list=()
quiet=""
work_dir=""
out_dir=""
gpg_key=""
gpg_sender=""
iso_name=""
iso_label=""
iso_uuid=""
iso_publisher=""
iso_application=""
iso_version=""
install_dir=""
arch=""
pacman_conf=""
packages=""
bootstrap_packages=""
pacstrap_dir=""
declare -i rm_work_dir=0
buildmodes=()
bootmodes=()
airootfs_image_type=""
airootfs_image_tool_options=()
cert_list=()
declare -A file_permissions=()
efibootimg=""
efiboot_files=()
# adapted from GRUB_EARLY_INITRD_LINUX_STOCK in https://git.savannah.gnu.org/cgit/grub.git/tree/util/grub-mkconfig.in
readonly ucodes=('intel-uc.img' 'intel-ucode.img' 'amd-uc.img' 'amd-ucode.img' 'early_ucode.cpio' 'microcode.cpio')


# Show an INFO message
# $1: message string
_msg_info() {
    local _msg="${1}"
    [[ "${quiet}" == "y" ]] || printf '[%s] INFO: %s\n' "${app_name}" "${_msg}"
}

# Show a WARNING message
# $1: message string
_msg_warning() {
    local _msg="${1}"
    printf '[%s] WARNING: %s\n' "${app_name}" "${_msg}" >&2
}

# Show an ERROR message then exit with status
# $1: message string
# $2: exit code number (with 0 does not exit)
_msg_error() {
    local _msg="${1}"
    local _error=${2}
    printf '[%s] ERROR: %s\n' "${app_name}" "${_msg}" >&2
    if (( _error > 0 )); then
        exit "${_error}"
    fi
}

# Show help usage, with an exit status.
# $1: exit status number.
_usage() {
    IFS='' read -r -d '' usagetext <<ENDUSAGETEXT || true
usage: ${app_name} [options] <profile_dir>
  options:
     -A <application> Set an application name for the ISO
                      Default: '${iso_application}'
     -C <file>        pacman configuration file.
                      Default: '${pacman_conf}'
     -D <install_dir> Set an install_dir. All files will be located here.
                      Default: '${install_dir}'
                      NOTE: Max 8 characters, use only [a-z0-9]
     -L <label>       Set the ISO volume label
                      Default: '${iso_label}'
     -P <publisher>   Set the ISO publisher
                      Default: '${iso_publisher}'
     -c [cert ..]     Provide certificates for codesigning of netboot artifacts as
                      well as the rootfs artifact.
                      Multiple files are provided as quoted, space delimited list.
                      The first file is considered as the signing certificate,
                      the second as the key and the third as the optional certificate authority.
     -g <gpg_key>     Set the PGP key ID to be used for signing the rootfs image.
                      Passed to gpg as the value for --default-key
     -G <mbox>        Set the PGP signer (must include an email address)
                      Passed to gpg as the value for --sender
     -h               This message
     -m [mode ..]     Build mode(s) to use (valid modes are: 'bootstrap', 'iso' and 'netboot').
                      Multiple build modes are provided as quoted, space delimited list.
     -o <out_dir>     Set the output directory
                      Default: '${out_dir}'
     -p [package ..]  Package(s) to install.
                      Multiple packages are provided as quoted, space delimited list.
     -r               Delete the working directory at the end.
     -v               Enable verbose output
     -w <work_dir>    Set the working directory
                      Default: '${work_dir}'

  profile_dir:        Directory of the archiso profile to build
ENDUSAGETEXT
    printf '%s' "${usagetext}"
    exit "${1}"
}

# Shows configuration options.
_show_config() {
    local build_date
    printf -v build_date '%(%FT%R%z)T' "${SOURCE_DATE_EPOCH}"
    _msg_info "${app_name} configuration settings"
    _msg_info "             Architecture:   ${arch}"
    _msg_info "        Working directory:   ${work_dir}"
    _msg_info "   Installation directory:   ${install_dir}"
    _msg_info "               Build date:   ${build_date}"
    _msg_info "         Output directory:   ${out_dir}"
    _msg_info "       Current build mode:   ${buildmode}"
    _msg_info "              Build modes:   ${buildmodes[*]}"
    _msg_info "                  GPG key:   ${gpg_key:-None}"
    _msg_info "               GPG signer:   ${gpg_sender:-None}"
    _msg_info "Code signing certificates:   ${cert_list[*]:-None}"
    _msg_info "                  Profile:   ${profile}"
    _msg_info "Pacman configuration file:   ${pacman_conf}"
    _msg_info "          Image file name:   ${image_name:-None}"
    _msg_info "         ISO volume label:   ${iso_label}"
    _msg_info "            ISO publisher:   ${iso_publisher}"
    _msg_info "          ISO application:   ${iso_application}"
    _msg_info "               Boot modes:   ${bootmodes[*]:-None}"
    _msg_info "            Packages File:   ${buildmode_packages}"
    _msg_info "                 Packages:   ${buildmode_pkg_list[*]}"
}

# Cleanup airootfs
_cleanup_pacstrap_dir() {
    _msg_info "Cleaning up in pacstrap location..."

    # Delete all files in /boot
    [[ -d "${pacstrap_dir}/boot" ]] && find "${pacstrap_dir}/boot" -mindepth 1 -delete
    # Delete pacman database sync cache files (*.tar.gz)
    [[ -d "${pacstrap_dir}/var/lib/pacman" ]] && find "${pacstrap_dir}/var/lib/pacman" -maxdepth 1 -type f -delete
    # Delete pacman database sync cache
    [[ -d "${pacstrap_dir}/var/lib/pacman/sync" ]] && find "${pacstrap_dir}/var/lib/pacman/sync" -delete
    # Delete pacman package cache
    [[ -d "${pacstrap_dir}/var/cache/pacman/pkg" ]] && find "${pacstrap_dir}/var/cache/pacman/pkg" -type f -delete
    # Delete all log files, keeps empty dirs.
    [[ -d "${pacstrap_dir}/var/log" ]] && find "${pacstrap_dir}/var/log" -type f -delete
    # Delete all temporary files and dirs
    [[ -d "${pacstrap_dir}/var/tmp" ]] && find "${pacstrap_dir}/var/tmp" -mindepth 1 -delete
    # Delete package pacman related files.
    find "${work_dir}" \( -name '*.pacnew' -o -name '*.pacsave' -o -name '*.pacorig' \) -delete
    # Create /etc/machine-id with special value 'uninitialized': the final id is
    # generated on first boot, systemd's first-boot mechanism applies (see machine-id(5))
    rm -f -- "${pacstrap_dir}/etc/machine-id"
    printf 'uninitialized\n' >"${pacstrap_dir}/etc/machine-id"

    _msg_info "Done!"
}

# Create a squashfs image and place it in the ISO 9660 file system.
# $@: options to pass to mksquashfs
_run_mksquashfs() {
    local mksquashfs_options=() image_path="${isofs_dir}/${install_dir}/${arch}/airootfs.sfs"
    rm -f -- "${image_path}"
    [[ ! "${quiet}" == "y" ]] || mksquashfs_options+=('-no-progress' '-quiet')
    mksquashfs "$@" "${image_path}" -noappend "${airootfs_image_tool_options[@]}" "${mksquashfs_options[@]}"
}

# Create an ext4 image containing the root file system and pack it inside a squashfs image.
# Save the squashfs image on the ISO 9660 file system.
_mkairootfs_ext4+squashfs() {
    local ext4_hash_seed mkfs_ext4_options=()
    [[ -e "${pacstrap_dir}" ]] || _msg_error "The path '${pacstrap_dir}' does not exist" 1

    _msg_info "Creating ext4 image of 32 GiB and copying '${pacstrap_dir}/' to it..."

    ext4_hash_seed="$(uuidgen --sha1 --namespace 93a870ff-8565-4cf3-a67b-f47299271a96 \
        --name "${SOURCE_DATE_EPOCH} ext4 hash seed")"
    mkfs_ext4_options=(
        '-d' "${pacstrap_dir}"
        '-O' '^has_journal,^resize_inode'
        '-E' "lazy_itable_init=0,root_owner=0:0,hash_seed=${ext4_hash_seed}"
        '-m' '0'
        '-F'
        '-U' 'clear'
    )
    [[ ! "${quiet}" == "y" ]] || mkfs_ext4_options+=('-q')
    rm -f -- "${pacstrap_dir}.img"
    E2FSPROGS_FAKE_TIME="${SOURCE_DATE_EPOCH}" mkfs.ext4 "${mkfs_ext4_options[@]}" -- "${pacstrap_dir}.img" 32G
    tune2fs -c 0 -i 0 -- "${pacstrap_dir}.img" >/dev/null
    _msg_info "Done!"

    install -d -m 0755 -- "${isofs_dir}/${install_dir}/${arch}"
    _msg_info "Creating SquashFS image, this may take some time..."
    _run_mksquashfs "${pacstrap_dir}.img"
    _msg_info "Done!"
    rm -- "${pacstrap_dir}.img"
}

# Create a squashfs image containing the root file system and saves it on the ISO 9660 file system.
_mkairootfs_squashfs() {
    [[ -e "${pacstrap_dir}" ]] || _msg_error "The path '${pacstrap_dir}' does not exist" 1

    install -d -m 0755 -- "${isofs_dir}/${install_dir}/${arch}"
    _msg_info "Creating SquashFS image, this may take some time..."
    _run_mksquashfs "${pacstrap_dir}"
}

# Create an EROFS image containing the root file system and saves it on the ISO 9660 file system.
_mkairootfs_erofs() {
    local fsuuid mkfs_erofs_options=()
    [[ -e "${pacstrap_dir}" ]] || _msg_error "The path '${pacstrap_dir}' does not exist" 1

    install -d -m 0755 -- "${isofs_dir}/${install_dir}/${arch}"
    local image_path="${isofs_dir}/${install_dir}/${arch}/airootfs.erofs"
    rm -f -- "${image_path}"
    [[ ! "${quiet}" == "y" ]] || mkfs_erofs_options+=('--quiet')
    # Generate reproducible file system UUID from SOURCE_DATE_EPOCH
    fsuuid="$(uuidgen --sha1 --namespace 93a870ff-8565-4cf3-a67b-f47299271a96 --name "${SOURCE_DATE_EPOCH}")"
    mkfs_erofs_options+=('-U' "${fsuuid}" "${airootfs_image_tool_options[@]}")
    _msg_info "Creating EROFS image, this may take some time..."
    mkfs.erofs "${mkfs_erofs_options[@]}" -- "${image_path}" "${pacstrap_dir}"
    _msg_info "Done!"
}

# Create checksum file for the rootfs image.
_mkchecksum() {
    _msg_info "Creating checksum file for self-test..."
    cd -- "${isofs_dir}/${install_dir}/${arch}"
    if [[ -e "${isofs_dir}/${install_dir}/${arch}/airootfs.sfs" ]]; then
        sha512sum airootfs.sfs >airootfs.sha512
    elif [[ -e "${isofs_dir}/${install_dir}/${arch}/airootfs.erofs" ]]; then
        sha512sum airootfs.erofs >airootfs.sha512
    fi
    cd -- "${OLDPWD}"
    _msg_info "Done!"
}

# GPG sign the root file system image.
_mk_pgp_signature() {
    local gpg_options=()
    local airootfs_image_filename="${1}"
    _msg_info "Signing rootfs image using GPG..."

    rm -f -- "${airootfs_image_filename}.sig"
    # Add gpg sender option if the value is provided
    [[ -z "${gpg_sender}" ]] || gpg_options+=('--sender' "${gpg_sender}")
    # always use the .sig file extension, as that is what mkinitcpio-archiso's hooks expect
    gpg --batch --no-armor --no-include-key-block --output "${airootfs_image_filename}.sig" --detach-sign \
        --default-key "${gpg_key}" "${gpg_options[@]}" "${airootfs_image_filename}"
    _msg_info "Done!"
}

# Helper function to run functions only one time.
# $1: function name
_run_once() {
    if [[ ! -e "${work_dir}/${run_once_mode}.${1}" ]]; then
        "$1"
        touch "${work_dir}/${run_once_mode}.${1}"
    fi
}

# Set up custom pacman.conf with custom cache and pacman hook directories.
_make_pacman_conf() {
    local _cache_dirs _system_cache_dirs _profile_cache_dirs
    _system_cache_dirs="$(pacman-conf CacheDir | tr '\n' ' ')"
    _profile_cache_dirs="$(pacman-conf --config "${pacman_conf}" CacheDir | tr '\n' ' ')"

    # Only use the profile's CacheDir, if it is not the default and not the same as the system cache dir.
    if [[ "${_profile_cache_dirs}" != "/var/cache/pacman/pkg" ]] \
        && [[ "${_system_cache_dirs}" != "${_profile_cache_dirs}" ]]; then
        _cache_dirs="${_profile_cache_dirs}"
    else
        _cache_dirs="${_system_cache_dirs}"
    fi

    _msg_info "Copying custom pacman.conf to work directory..."
    _msg_info "Using pacman CacheDir: ${_cache_dirs}"
    # take the profile pacman.conf and strip all settings that would break in chroot when using pacman -r
    # append CacheDir and HookDir to [options] section
    # HookDir is *always* set to the airootfs' override directory
    # see `man 8 pacman` for further info
    pacman-conf --config "${pacman_conf}" \
        | sed "/CacheDir/d;/DBPath/d;/HookDir/d;/LogFile/d;/RootDir/d;/\[options\]/a CacheDir = ${_cache_dirs}
        /\[options\]/a HookDir = ${pacstrap_dir}/etc/pacman.d/hooks/" >"${work_dir}/${buildmode}.pacman.conf"
}

# Prepare working directory and copy custom root file system files.
_make_custom_airootfs() {
    local passwd=()
    local filename permissions

    install -d -m 0755 -o 0 -g 0 -- "${pacstrap_dir}"

    if [[ -d "${profile}/airootfs" ]]; then
        _msg_info "Copying custom airootfs files..."
        cp -af --no-preserve=ownership,mode -- "${profile}/airootfs/." "${pacstrap_dir}"
        # Set ownership and mode for files and directories
        for filename in "${!file_permissions[@]}"; do
            IFS=':' read -ra permissions <<<"${file_permissions["${filename}"]}"
            # Prevent file path traversal outside of $pacstrap_dir
            if [[ "$(realpath -q -- "${pacstrap_dir}${filename}")" != "${pacstrap_dir}"* ]]; then
                _msg_error "Failed to set permissions on '${pacstrap_dir}${filename}'. Outside of valid path." 1
            # Warn if the file does not exist
            elif [[ ! -e "${pacstrap_dir}${filename}" ]]; then
                _msg_warning "Cannot change permissions of '${pacstrap_dir}${filename}'. The file or directory does not exist."
            else
                if [[ "${filename: -1}" == "/" ]]; then
                    chown -fhR -- "${permissions[0]}:${permissions[1]}" "${pacstrap_dir}${filename}"
                    chmod -fR -- "${permissions[2]}" "${pacstrap_dir}${filename}"
                else
                    chown -fh -- "${permissions[0]}:${permissions[1]}" "${pacstrap_dir}${filename}"
                    chmod -f -- "${permissions[2]}" "${pacstrap_dir}${filename}"
                fi
            fi
        done
        _msg_info "Done!"
    fi
}

# Install desired packages to the root file system
_make_packages() {
    _msg_info "Installing packages to '${pacstrap_dir}/'..."

    if [[ -v gpg_publickey ]]; then
        exec {ARCHISO_GNUPG_FD}<"$gpg_publickey"
        export ARCHISO_GNUPG_FD
    fi
    if [[ -v cert_list[0] ]]; then
        exec {ARCHISO_TLS_FD}<"${cert_list[0]}"
        export ARCHISO_TLS_FD
    fi
    if [[ -v cert_list[2] ]]; then
        exec {ARCHISO_TLSCA_FD}<"${cert_list[2]}"
        export ARCHISO_TLSCA_FD
    fi


    # Unset TMPDIR to work around https://bugs.archlinux.org/task/70580
    if [[ "${quiet}" = "y" ]]; then
        env -u TMPDIR pacstrap -C "${work_dir}/${buildmode}.pacman.conf" -c -G -M -- "${pacstrap_dir}" "${buildmode_pkg_list[@]}" &>/dev/null
    else
        env -u TMPDIR pacstrap -C "${work_dir}/${buildmode}.pacman.conf" -c -G -M -- "${pacstrap_dir}" "${buildmode_pkg_list[@]}"
    fi

    if [[ -v cert_list[0] ]]; then
        exec {ARCHISO_TLS_FD}<&-
        unset ARCHISO_TLS_FD
    fi
    if [[ -v cert_list[2] ]]; then
        exec {ARCHISO_TLSCA_FD}<&-
        unset ARCHISO_TLSCA_FD
    fi
    if [[ -v gpg_publickey ]]; then
        exec {ARCHISO_GNUPG_FD}<&-
        unset ARCHISO_GNUPG_FD
    fi

    _msg_info "Done! Packages installed successfully."
}

# Customize installation.
_make_customize_airootfs() {
    local passwd=()

    if [[ -e "${profile}/airootfs/etc/passwd" ]]; then
        _msg_info "Copying /etc/skel/* to user homes..."
        while IFS=':' read -a passwd -r; do
            # Only operate on UIDs in range 1000–59999
            (( passwd[2] >= 1000 && passwd[2] < 60000 )) || continue
            # Skip invalid home directories
            [[ "${passwd[5]}" == '/' ]] && continue
            [[ -z "${passwd[5]}" ]] && continue
            # Prevent path traversal outside of $pacstrap_dir
            if [[ "$(realpath -q -- "${pacstrap_dir}${passwd[5]}")" == "${pacstrap_dir}"* ]]; then
                if [[ ! -d "${pacstrap_dir}${passwd[5]}" ]]; then
                    install -d -m 0750 -o "${passwd[2]}" -g "${passwd[3]}" -- "${pacstrap_dir}${passwd[5]}"
                fi
                cp -dRT --update=none --preserve=mode,timestamps,links -- "${pacstrap_dir}/etc/skel/." "${pacstrap_dir}${passwd[5]}"
                chmod -f 0750 -- "${pacstrap_dir}${passwd[5]}"
                chown -hR -- "${passwd[2]}:${passwd[3]}" "${pacstrap_dir}${passwd[5]}"
            else
                _msg_error "Failed to set permissions on '${pacstrap_dir}${passwd[5]}'. Outside of valid path." 1
            fi
        done <"${profile}/airootfs/etc/passwd"
        _msg_info "Done!"
    fi

    if [[ -e "${pacstrap_dir}/root/customize_airootfs.sh" ]]; then
        _msg_info "Running customize_airootfs.sh in '${pacstrap_dir}' chroot..."
        _msg_warning "customize_airootfs.sh is deprecated! Support for it will be removed in a future archiso version."
        chmod -f -- +x "${pacstrap_dir}/root/customize_airootfs.sh"
        # Unset TMPDIR to work around https://bugs.archlinux.org/task/70580
        eval -- env -u TMPDIR arch-chroot "${pacstrap_dir}" "/root/customize_airootfs.sh"
        rm -- "${pacstrap_dir}/root/customize_airootfs.sh"
        _msg_info "Done! customize_airootfs.sh run successfully."
    fi
}

# Set up boot loaders
_make_bootmodes() {
    local bootmode
    for bootmode in "${bootmodes[@]}"; do
        _run_once "_make_bootmode_${bootmode}"
    done
}

# Copy kernel and initramfs to ISO 9660
_make_boot_on_iso9660() {
    local ucode_image
    _msg_info "Preparing kernel and initramfs for the ISO 9660 file system..."
    install -d -m 0755 -- "${isofs_dir}/${install_dir}/boot/${arch}"
    install -m 0644 -- "${pacstrap_dir}/boot/initramfs-"*".img" "${isofs_dir}/${install_dir}/boot/${arch}/"
    install -m 0644 -- "${pacstrap_dir}/boot/vmlinuz-"* "${isofs_dir}/${install_dir}/boot/${arch}/"

    for ucode_image in "${ucodes[@]}"; do
        if [[ -e "${pacstrap_dir}/boot/${ucode_image}" ]]; then
            install -m 0644 -- "${pacstrap_dir}/boot/${ucode_image}" "${isofs_dir}/${install_dir}/boot/"
            if [[ -e "${pacstrap_dir}/usr/share/licenses/${ucode_image%.*}/" ]]; then
                install -d -m 0755 -- "${isofs_dir}/${install_dir}/boot/licenses/${ucode_image%.*}/"
                install -m 0644 -- "${pacstrap_dir}/usr/share/licenses/${ucode_image%.*}/"* \
                    "${isofs_dir}/${install_dir}/boot/licenses/${ucode_image%.*}/"
            fi
        fi
    done
    _msg_info "Done!"
}

# Prepare syslinux for booting from MBR (isohybrid)
_make_bootmode_bios.syslinux.mbr() {
    _msg_info "Setting up SYSLINUX for BIOS booting from a disk..."
    install -d -m 0755 -- "${isofs_dir}/boot/syslinux"
    for _cfg in "${profile}/syslinux/"*.cfg; do
        sed "s|%ARCHISO_LABEL%|${iso_label}|g;
             s|%ARCHISO_UUID%|${iso_uuid}|g;
             s|%INSTALL_DIR%|${install_dir}|g;
             s|%ARCH%|${arch}|g" \
            "${_cfg}" >"${isofs_dir}/boot/syslinux/${_cfg##*/}"
    done
    if [[ -e "${profile}/syslinux/splash.png" ]]; then
        install -m 0644 -- "${profile}/syslinux/splash.png" "${isofs_dir}/boot/syslinux/"
    fi
    install -m 0644 -- "${pacstrap_dir}/usr/lib/syslinux/bios/"*.c32 "${isofs_dir}/boot/syslinux/"
    install -m 0644 -- "${pacstrap_dir}/usr/lib/syslinux/bios/lpxelinux.0" "${isofs_dir}/boot/syslinux/"
    install -m 0644 -- "${pacstrap_dir}/usr/lib/syslinux/bios/memdisk" "${isofs_dir}/boot/syslinux/"

    _run_once _make_boot_on_iso9660

    if [[ -e "${isofs_dir}/boot/syslinux/hdt.c32" ]]; then
        install -d -m 0755 -- "${isofs_dir}/boot/syslinux/hdt"
        if [[ -e "${pacstrap_dir}/usr/share/hwdata/pci.ids" ]]; then
            gzip -cn9 "${pacstrap_dir}/usr/share/hwdata/pci.ids" > \
                "${isofs_dir}/boot/syslinux/hdt/pciids.gz"
        fi
        find "${pacstrap_dir}/usr/lib/modules" -name 'modules.alias' -print -exec gzip -cn9 '{}' ';' -quit > \
            "${isofs_dir}/boot/syslinux/hdt/modalias.gz"
    fi

    # Add other aditional/extra files to ${install_dir}/boot/
    if [[ -e "${pacstrap_dir}/boot/memtest86+/memtest.bin" ]]; then
        install -d -m 0755 -- "${isofs_dir}/boot/memtest86+/"
        # rename for PXE: https://wiki.archlinux.org/title/Syslinux#Using_memtest
        install -m 0644 -- "${pacstrap_dir}/boot/memtest86+/memtest.bin" "${isofs_dir}/boot/memtest86+/memtest"
        install -m 0644 -- "${pacstrap_dir}/usr/share/licenses/common/GPL2/license.txt" "${isofs_dir}/boot/memtest86+/"
    fi
    _msg_info "Done! SYSLINUX set up for BIOS booting from a disk successfully."
}

# Prepare syslinux for El-Torito booting
_make_bootmode_bios.syslinux.eltorito() {
    _msg_info "Setting up SYSLINUX for BIOS booting from an optical disc..."
    install -d -m 0755 -- "${isofs_dir}/boot/syslinux"
    install -m 0644 -- "${pacstrap_dir}/usr/lib/syslinux/bios/isolinux.bin" "${isofs_dir}/boot/syslinux/"
    install -m 0644 -- "${pacstrap_dir}/usr/lib/syslinux/bios/isohdpfx.bin" "${isofs_dir}/boot/syslinux/"

    # ISOLINUX and SYSLINUX installation is shared
    _run_once _make_bootmode_bios.syslinux.mbr

    _msg_info "Done! SYSLINUX set up for BIOS booting from an optical disc successfully."
}

# Copy kernel and initramfs to FAT image
_make_boot_on_fat() {
    local ucode_image all_ucode_images=()
    _msg_info "Preparing kernel and initramfs for the FAT file system..."
    mmd -i "${efibootimg}" \
        "::/${install_dir}" "::/${install_dir}/boot" "::/${install_dir}/boot/${arch}"
    mcopy -i "${efibootimg}" "${pacstrap_dir}/boot/vmlinuz-"* \
        "${pacstrap_dir}/boot/initramfs-"*".img" "::/${install_dir}/boot/${arch}/"
    for ucode_image in "${ucodes[@]}"; do
        if [[ -e "${pacstrap_dir}/boot/${ucode_image}" ]]; then
            all_ucode_images+=("${pacstrap_dir}/boot/${ucode_image}")
        fi
    done
    if (( ${#all_ucode_images[@]} )); then
        mcopy -i "${efibootimg}" "${all_ucode_images[@]}" "::/${install_dir}/boot/"
    fi
    _msg_info "Done!"
}

# Create a FAT image (efiboot.img) which will serve as the EFI system partition
# $1: image size in bytes
_make_efibootimg() {
    local imgsize_kib="0"
    local imgsize_bytes=${1}

    if (( imgsize_bytes < 2*1024*1024 )); then
        _msg_info "Validating '${bootmode}': efiboot.img size is ${imgsize_bytes} bytes is less than 2 MiB! Bumping up to 2 MiB"
        imgsize_bytes=$((2*1024*1024))
    fi

    # Convert from bytes to KiB and round up to the next full MiB with an additional MiB for reserved sectors.
    imgsize_kib="$(
        awk 'function ceil(x){return int(x)+(x>int(x))}
            function byte_to_kib(x){return x/1024}
            function mib_to_kib(x){return x*1024}
            END {print mib_to_kib(ceil((byte_to_kib($1)+1024)/1024))}' <<<"${imgsize_bytes}"
    )"
    # The FAT image must be created with mkfs.fat not mformat, as some systems have issues with mformat made images:
    # https://lists.gnu.org/archive/html/grub-devel/2019-04/msg00099.html
    rm -f -- "${efibootimg}"
    _msg_info "Creating FAT image of size: ${imgsize_kib} KiB..."
    if [[ "${quiet}" == "y" ]]; then
        # mkfs.fat does not have a -q/--quiet option, so redirect stdout to /dev/null instead
        # https://github.com/dosfstools/dosfstools/issues/103
        mkfs.fat -C -n ARCHISO_EFI "${efibootimg}" "${imgsize_kib}" >/dev/null
    else
        mkfs.fat -C -n ARCHISO_EFI "${efibootimg}" "${imgsize_kib}"
    fi

    # Create the default/fallback boot path in which a boot loaders will be placed later.
    mmd -i "${efibootimg}" ::/EFI ::/EFI/BOOT
}

# Copy GRUB files to ISO 9660 which is used by both IA32 UEFI and x64 UEFI
_make_common_bootmode_grub_copy_to_isofs() {
    local files_to_copy=()

    files_to_copy+=("${work_dir}/grub/"*)
    if compgen -G "${profile}/grub/!(*.cfg)" &>/dev/null; then
        files_to_copy+=("${profile}/grub/"!(*.cfg))
    fi
    install -d -m 0755 -- "${isofs_dir}/boot/grub"
    cp -r --remove-destination -- "${files_to_copy[@]}" "${isofs_dir}/boot/grub/"
}

# Prepare GRUB configuration files
_make_common_bootmode_grub_cfg() {
    local _cfg search_filename

    install -d -- "${work_dir}/grub"

    # Create a /boot/grub/YYYY-mm-dd-HH-MM-SS-00.uuid file on ISO 9660. GRUB will search for it to find the ISO
    # volume. This is similar to what grub-mkrescue does, except it places the file in /.disk/, but we opt to use a
    # directory that does not start with a dot to avoid it being accidentally missed when copying the ISO's contents.
    : >"${work_dir}/grub/${iso_uuid}.uuid"
    search_filename="/boot/grub/${iso_uuid}.uuid"

    # Fill GRUB configuration files
    for _cfg in "${profile}/grub/"*'.cfg'; do
        sed "s|%ARCHISO_LABEL%|${iso_label}|g;
             s|%ARCHISO_UUID%|${iso_uuid}|g;
             s|%INSTALL_DIR%|${install_dir}|g;
             s|%ARCH%|${arch}|g;
             s|%ARCHISO_SEARCH_FILENAME%|${search_filename}|g" \
            "${_cfg}" >"${work_dir}/grub/${_cfg##*/}"
    done

    # Prepare grub.cfg that will be embedded inside the GRUB binaries
    IFS='' read -r -d '' grubembedcfg <<'EOF' || true
if ! [ -d "$cmdpath" ]; then
    # On some firmware, GRUB has a wrong cmdpath when booted from an optical disc. During El Torito boot, GRUB is
    # launched from a case-insensitive FAT-formatted EFI system partition, but it seemingly cannot access that partition
    # and sets cmdpath to the whole cd# device which has case-sensitive ISO 9660 + Rock Ridge + Joliet file systems.
    # See https://gitlab.archlinux.org/archlinux/archiso/-/issues/183 and https://savannah.gnu.org/bugs/?62886
    if regexp --set=1:archiso_bootdevice '^\(([^)]+)\)\/?[Ee][Ff][Ii]\/[Bb][Oo][Oo][Tt]\/?$' "${cmdpath}"; then
        set cmdpath="(${archiso_bootdevice})/EFI/BOOT"
        set ARCHISO_HINT="${archiso_bootdevice}"
    fi
fi

# Prepare a hint for the search command using the device in cmdpath
if [ -z "${ARCHISO_HINT}" ]; then
    regexp --set=1:ARCHISO_HINT '^\(([^)]+)\)' "${cmdpath}"
fi

# Search for the ISO volume
if search --no-floppy --set=archiso_device --file '%ARCHISO_SEARCH_FILENAME%' --hint "${ARCHISO_HINT}"; then
    set ARCHISO_HINT="${archiso_device}"
    if probe --set ARCHISO_UUID --fs-uuid "${ARCHISO_HINT}"; then
        export ARCHISO_UUID
    fi
else
    echo "Could not find a volume with a '%ARCHISO_SEARCH_FILENAME%' file on it!"
fi

# Load grub.cfg
if [ "${ARCHISO_HINT}" == 'memdisk' -o -z "${ARCHISO_HINT}" ]; then
    echo 'Could not find the ISO volume!'
elif [ -e "(${ARCHISO_HINT})/boot/grub/grub.cfg" ]; then
    export ARCHISO_HINT
    set root="${ARCHISO_HINT}"
    configfile "(${ARCHISO_HINT})/boot/grub/grub.cfg"
else
    echo "File '(${ARCHISO_HINT})/boot/grub/grub.cfg' not found!"
fi
EOF
    grubembedcfg="${grubembedcfg//'%ARCHISO_SEARCH_FILENAME%'/"${search_filename}"}"
    printf '%s\n' "$grubembedcfg" >"${work_dir}/grub-embed.cfg"

    # Write grubenv
    printf '%.1024s' \
        "$(printf '# GRUB Environment Block\nNAME=%s\nVERSION=%s\nARCHISO_LABEL=%s\nINSTALL_DIR=%s\nARCH=%s\nARCHISO_SEARCH_FILENAME=%s\n%s' \
            "${iso_name}" \
            "${iso_version}" \
            "${iso_label}" \
            "${install_dir}" \
            "${arch}" \
            "${search_filename}" \
            "$(printf '%0.1s' "#"{1..1024})")" \
        >"${work_dir}/grub/grubenv"
}

_make_bootmode_uefi-ia32.grub.esp() {
    local grubmodules=()

    # Prepare configuration files
    _run_once _make_common_bootmode_grub_cfg

    # Create EFI binary
    # Module list from https://bugs.archlinux.org/task/71382#comment202911
    grubmodules=(all_video at_keyboard boot btrfs cat chain configfile echo efifwsetup efinet exfat ext2 f2fs fat font \
                 gfxmenu gfxterm gzio halt hfsplus iso9660 jpeg keylayouts linux loadenv loopback lsefi lsefimmap \
                 minicmd normal ntfs ntfscomp part_apple part_gpt part_msdos png read reboot regexp search \
                 search_fs_file search_fs_uuid search_label serial sleep tpm udf usb usbserial_common usbserial_ftdi \
                 usbserial_pl2303 usbserial_usbdebug video xfs zstd)
    grub-mkstandalone -O i386-efi \
        --modules="${grubmodules[*]}" \
        --locales="en@quot" \
        --themes="" \
        --sbat=/usr/share/grub/sbat.csv \
        --disable-shim-lock \
        -o "${work_dir}/BOOTIA32.EFI" "boot/grub/grub.cfg=${work_dir}/grub-embed.cfg"
    # Add GRUB to the list of files used to calculate the required FAT image size.
    efiboot_files+=("${work_dir}/BOOTIA32.EFI"
                    "${pacstrap_dir}/usr/share/edk2-shell/ia32/Shell_Full.efi")

    if [[ " ${bootmodes[*]} " =~ uefi-x64.systemd-boot.esp ]]; then
        # TODO: Remove this branch.
        _run_once _make_bootmode_uefi-x64.systemd-boot.esp
    elif [[ " ${bootmodes[*]} " =~ uefi-x64.grub.esp ]]; then
        _run_once _make_bootmode_uefi-x64.grub.esp
    else
        efiboot_imgsize="$(du -bcs -- "${efiboot_files[@]}" 2>/dev/null | awk 'END { print $1 }')"
        # Create a FAT image for the EFI system partition
        _make_efibootimg "$efiboot_imgsize"
    fi

    # Copy GRUB EFI binary to the default/fallback boot path
    mcopy -i "${efibootimg}" "${work_dir}/BOOTIA32.EFI" ::/EFI/BOOT/BOOTIA32.EFI

    # Copy GRUB files
    _run_once _make_common_bootmode_grub_copy_to_isofs

    if [[ -e "${pacstrap_dir}/usr/share/edk2-shell/ia32/Shell_Full.efi" ]]; then
        mcopy -i "${efibootimg}" "${pacstrap_dir}/usr/share/edk2-shell/ia32/Shell_Full.efi" ::/shellia32.efi
    fi

    _msg_info "Done! GRUB set up for UEFI booting successfully."
}

# Prepare GRUB for El Torito booting
_make_bootmode_uefi-ia32.grub.eltorito() {
    # El Torito UEFI boot requires an image containing the EFI system partition.
    # uefi-ia32.grub.eltorito has the same requirements as uefi-ia32.grub.esp
    _run_once _make_bootmode_uefi-ia32.grub.esp

    # Prepare configuration files
    _run_once _make_common_bootmode_grub_cfg

    # Additionally set up systemd-boot in ISO 9660. This allows creating a medium for the live environment by using
    # manual partitioning and simply copying the ISO 9660 file system contents.
    # This is not related to El Torito booting and no firmware uses these files.
    _msg_info "Preparing an /EFI directory for the ISO 9660 file system..."
    install -d -m 0755 -- "${isofs_dir}/EFI/BOOT"

    # Copy GRUB EFI binary to the default/fallback boot path
    install -m 0644 -- "${work_dir}/BOOTIA32.EFI" "${isofs_dir}/EFI/BOOT/BOOTIA32.EFI"

    # Copy GRUB configuration files
    _run_once _make_common_bootmode_grub_copy_to_isofs

    # edk2-shell based UEFI shell
    if [[ -e "${pacstrap_dir}/usr/share/edk2-shell/ia32/Shell_Full.efi" ]]; then
        install -m 0644 -- "${pacstrap_dir}/usr/share/edk2-shell/ia32/Shell_Full.efi" "${isofs_dir}/shellia32.efi"
    fi

    _msg_info "Done!"
}

_make_bootmode_uefi-x64.grub.esp() {
    local grubmodules=()

    # Prepare configuration files
    _run_once _make_common_bootmode_grub_cfg

    # Create EFI binary
    # Module list from https://bugs.archlinux.org/task/71382#comment202911
    grubmodules=(all_video at_keyboard boot btrfs cat chain configfile echo efifwsetup efinet exfat ext2 f2fs fat font \
                 gfxmenu gfxterm gzio halt hfsplus iso9660 jpeg keylayouts linux loadenv loopback lsefi lsefimmap \
                 minicmd normal ntfs ntfscomp part_apple part_gpt part_msdos png read reboot regexp search \
                 search_fs_file search_fs_uuid search_label serial sleep tpm udf usb usbserial_common usbserial_ftdi \
                 usbserial_pl2303 usbserial_usbdebug video xfs zstd)
    grub-mkstandalone -O x86_64-efi \
        --modules="${grubmodules[*]}" \
        --locales="en@quot" \
        --themes="" \
        --sbat=/usr/share/grub/sbat.csv \
        --disable-shim-lock \
        -o "${work_dir}/BOOTx64.EFI" "boot/grub/grub.cfg=${work_dir}/grub-embed.cfg"
    # Add GRUB to the list of files used to calculate the required FAT image size.
    efiboot_files+=("${work_dir}/BOOTx64.EFI"
                    "${pacstrap_dir}/usr/share/edk2-shell/x64/Shell_Full.efi")

    efiboot_imgsize="$(du -bcs -- "${efiboot_files[@]}" 2>/dev/null | awk 'END { print $1 }')"

    # Create a FAT image for the EFI system partition
    _make_efibootimg "$efiboot_imgsize"

    # Copy GRUB EFI binary to the default/fallback boot path
    mcopy -i "${efibootimg}" "${work_dir}/BOOTx64.EFI" ::/EFI/BOOT/BOOTx64.EFI

    # Copy GRUB files
    _run_once _make_common_bootmode_grub_copy_to_isofs

    if [[ -e "${pacstrap_dir}/usr/share/edk2-shell/x64/Shell_Full.efi" ]]; then
        mcopy -i "${efibootimg}" "${pacstrap_dir}/usr/share/edk2-shell/x64/Shell_Full.efi" ::/shellx64.efi
    fi

    # Add other aditional/extra files to ${install_dir}/boot/
    if [[ -e "${pacstrap_dir}/boot/memtest86+/memtest.efi" ]]; then
        install -d -m 0755 -- "${isofs_dir}/boot/memtest86+/"
        install -m 0644 -- "${pacstrap_dir}/boot/memtest86+/memtest.efi" "${isofs_dir}/boot/memtest86+/memtest.efi"
        install -m 0644 -- "${pacstrap_dir}/usr/share/licenses/common/GPL2/license.txt" "${isofs_dir}/boot/memtest86+/"
    fi

    _msg_info "Done! GRUB set up for UEFI booting successfully."
}

# Prepare GRUB for El Torito booting
_make_bootmode_uefi-x64.grub.eltorito() {
    # El Torito UEFI boot requires an image containing the EFI system partition.
    # uefi-x64.grub.eltorito has the same requirements as uefi-x64.grub.esp
    _run_once _make_bootmode_uefi-x64.grub.esp

    # Prepare configuration files
    _run_once _make_common_bootmode_grub_cfg

    # Additionally set up systemd-boot in ISO 9660. This allows creating a medium for the live environment by using
    # manual partitioning and simply copying the ISO 9660 file system contents.
    # This is not related to El Torito booting and no firmware uses these files.
    _msg_info "Preparing an /EFI directory for the ISO 9660 file system..."
    install -d -m 0755 -- "${isofs_dir}/EFI/BOOT"

    # Copy GRUB EFI binary to the default/fallback boot path
    install -m 0644 -- "${work_dir}/BOOTx64.EFI" "${isofs_dir}/EFI/BOOT/BOOTx64.EFI"

    # Copy GRUB files
    _run_once _make_common_bootmode_grub_copy_to_isofs

    # edk2-shell based UEFI shell
    if [[ -e "${pacstrap_dir}/usr/share/edk2-shell/x64/Shell_Full.efi" ]]; then
        install -m 0644 -- "${pacstrap_dir}/usr/share/edk2-shell/x64/Shell_Full.efi" "${isofs_dir}/shellx64.efi"
    fi

    _msg_info "Done!"
}

_make_common_bootmode_systemd-boot() {
    local _file efiboot_imgsize
    local _available_ucodes=()

    for _file in "${ucodes[@]}"; do
        if [[ -e "${pacstrap_dir}/boot/${_file}" ]]; then
            _available_ucodes+=("${pacstrap_dir}/boot/${_file}")
        fi
    done
    # Calculate the required FAT image size in bytes
    # shellcheck disable=SC2076
    if [[ " ${bootmodes[*]} " =~ ' uefi-x64.systemd-boot.esp ' || " ${bootmodes[*]} " =~ ' uefi-x64.systemd-boot.eltorito ' ]]; then
        efiboot_files+=("${pacstrap_dir}/usr/lib/systemd/boot/efi/systemd-bootx64.efi"
                        "${pacstrap_dir}/usr/share/edk2-shell/x64/Shell_Full.efi")
    fi
    # shellcheck disable=SC2076
    if [[ " ${bootmodes[*]} " =~ ' uefi-ia32.systemd-boot.esp ' || " ${bootmodes[*]} " =~ ' uefi-ia32.systemd-boot.eltorito ' ]]; then
        efiboot_files+=("${pacstrap_dir}/usr/lib/systemd/boot/efi/systemd-bootia32.efi"
                        "${pacstrap_dir}/usr/share/edk2-shell/ia32/Shell_Full.efi")
    fi
    efiboot_files+=("${profile}/efiboot/"
                    "${pacstrap_dir}/boot/vmlinuz-"*
                    "${pacstrap_dir}/boot/initramfs-"*".img"
                    "${_available_ucodes[@]}")
    efiboot_imgsize="$(du -bcs -- "${efiboot_files[@]}" 2>/dev/null | awk 'END { print $1 }')"
    # Create a FAT image for the EFI system partition
    _make_efibootimg "$efiboot_imgsize"
}

_make_common_bootmode_systemd-boot_conf.isofs() {
    local _conf

    # Copy systemd-boot configuration files
    install -d -m 0755 -- "${isofs_dir}/loader/entries"
    install -m 0644 -- "${profile}/efiboot/loader/loader.conf" "${isofs_dir}/loader/"
    for _conf in "${profile}/efiboot/loader/entries/"*".conf"; do
        sed "s|%ARCHISO_LABEL%|${iso_label}|g;
             s|%INSTALL_DIR%|${install_dir}|g;
             s|%ARCH%|${arch}|g" \
            "${_conf}" >"${isofs_dir}/loader/entries/${_conf##*/}"
    done
}

_make_common_bootmode_systemd-boot_conf.esp() {
    local _conf

    # Copy systemd-boot configuration files
    mmd -i "${efibootimg}" ::/loader ::/loader/entries
    mcopy -i "${efibootimg}" "${profile}/efiboot/loader/loader.conf" ::/loader/
    for _conf in "${profile}/efiboot/loader/entries/"*".conf"; do
        sed "s|%ARCHISO_LABEL%|${iso_label}|g;
             s|%ARCHISO_UUID%|${iso_uuid}|g;
             s|%INSTALL_DIR%|${install_dir}|g;
             s|%ARCH%|${arch}|g" \
            "${_conf}" | mcopy -i "${efibootimg}" - "::/loader/entries/${_conf##*/}"
    done
}

# Prepare systemd-boot for booting when written to a disk (isohybrid)
_make_bootmode_uefi-x64.systemd-boot.esp() {
    _msg_info "Setting up systemd-boot for x64 UEFI booting..."

    _run_once _make_common_bootmode_systemd-boot

    # Copy systemd-boot EFI binary to the default/fallback boot path
    mcopy -i "${efibootimg}" \
        "${pacstrap_dir}/usr/lib/systemd/boot/efi/systemd-bootx64.efi" ::/EFI/BOOT/BOOTx64.EFI

    # Copy systemd-boot configuration files
    _run_once _make_common_bootmode_systemd-boot_conf.esp

    # shellx64.efi is picked up automatically when on /
    if [[ -e "${pacstrap_dir}/usr/share/edk2-shell/x64/Shell_Full.efi" ]]; then
        mcopy -i "${efibootimg}" \
            "${pacstrap_dir}/usr/share/edk2-shell/x64/Shell_Full.efi" ::/shellx64.efi
    fi

    # Copy kernel and initramfs to FAT image.
    # systemd-boot can only access files from the EFI system partition it was launched from.
    _run_once _make_boot_on_fat

    _msg_info "Done! systemd-boot set up for x64 UEFI booting successfully."
}

# Prepare systemd-boot for El Torito booting
_make_bootmode_uefi-x64.systemd-boot.eltorito() {
    # El Torito UEFI boot requires an image containing the EFI system partition.
    # uefi-x64.systemd-boot.eltorito has the same requirements as uefi-x64.systemd-boot.esp
    _run_once _make_bootmode_uefi-x64.systemd-boot.esp

    # Additionally set up systemd-boot in ISO 9660. This allows creating a medium for the live environment by using
    # manual partitioning and simply copying the ISO 9660 file system contents.
    # This is not related to El Torito booting and no firmware uses these files.
    _msg_info "Preparing an /EFI directory for the ISO 9660 file system..."
    install -d -m 0755 -- "${isofs_dir}/EFI/BOOT"

    # Copy systemd-boot EFI binary to the default/fallback boot path
    install -m 0644 -- "${pacstrap_dir}/usr/lib/systemd/boot/efi/systemd-bootx64.efi" \
        "${isofs_dir}/EFI/BOOT/BOOTx64.EFI"

    # Copy systemd-boot configuration files
    _run_once _make_common_bootmode_systemd-boot_conf.isofs

    # edk2-shell based UEFI shell
    # shellx64.efi is picked up automatically when on /
    if [[ -e "${pacstrap_dir}/usr/share/edk2-shell/x64/Shell_Full.efi" ]]; then
        install -m 0644 -- "${pacstrap_dir}/usr/share/edk2-shell/x64/Shell_Full.efi" "${isofs_dir}/shellx64.efi"
    fi

    _msg_info "Done!"
}

_make_bootmode_uefi-ia32.systemd-boot.esp() {
    _msg_info "Setting up systemd-boot for IA32 UEFI booting..."

    _run_once _make_common_bootmode_systemd-boot

    # Copy systemd-boot EFI binary to the default/fallback boot path
    mcopy -i "${efibootimg}" \
        "${pacstrap_dir}/usr/lib/systemd/boot/efi/systemd-bootia32.efi" ::/EFI/BOOT/BOOTIA32.EFI

    # Copy systemd-boot configuration files
    _run_once _make_common_bootmode_systemd-boot_conf.esp

    # shellia32.efi is picked up automatically when on /
    if [[ -e "${pacstrap_dir}/usr/share/edk2-shell/ia32/Shell_Full.efi" ]]; then
        mcopy -i "${efibootimg}" \
            "${pacstrap_dir}/usr/share/edk2-shell/ia32/Shell_Full.efi" ::/shellia32.efi
    fi

    # Copy kernel and initramfs to FAT image.
    # systemd-boot can only access files from the EFI system partition it was launched from.
    _run_once _make_boot_on_fat

    _msg_info "Done! systemd-boot set up for IA32 UEFI booting successfully."
}

_make_bootmode_uefi-ia32.systemd-boot.eltorito() {
    # El Torito UEFI boot requires an image containing the EFI system partition.
    # uefi-ia32.systemd-boot.eltorito has the same requirements as uefi-ia32.systemd-boot.esp
    _run_once _make_bootmode_uefi-ia32.systemd-boot.esp

    # Additionally set up systemd-boot in ISO 9660. This allows creating a medium for the live environment by using
    # manual partitioning and simply copying the ISO 9660 file system contents.
    # This is not related to El Torito booting and no firmware uses these files.
    _msg_info "Preparing an /EFI directory for the ISO 9660 file system..."
    install -d -m 0755 -- "${isofs_dir}/EFI/BOOT"

    # Copy systemd-boot EFI binary to the default/fallback boot path
    install -m 0644 -- "${pacstrap_dir}/usr/lib/systemd/boot/efi/systemd-bootia32.efi" \
        "${isofs_dir}/EFI/BOOT/BOOTIA32.EFI"

    # Copy systemd-boot configuration files
    _run_once _make_common_bootmode_systemd-boot_conf.isofs

    # edk2-shell based UEFI shell
    # shellia32.efi is picked up automatically when on /
    if [[ -e "${pacstrap_dir}/usr/share/edk2-shell/ia32/Shell_Full.efi" ]]; then
        install -m 0644 -- "${pacstrap_dir}/usr/share/edk2-shell/ia32/Shell_Full.efi" "${isofs_dir}/shellia32.efi"
    fi

    _msg_info "Done!"
}

_validate_requirements_bootmode_bios.syslinux.mbr() {
    # bios.syslinux.mbr requires bios.syslinux.eltorito
    # shellcheck disable=SC2076
    if [[ ! " ${bootmodes[*]} " =~ ' bios.syslinux.eltorito ' ]]; then
        (( validation_error=validation_error+1 ))
        _msg_error "Using 'bios.syslinux.mbr' boot mode without 'bios.syslinux.eltorito' is not supported." 0
    fi

    # Check if the syslinux package is in the package list
    # shellcheck disable=SC2076
    if [[ ! " ${pkg_list[*]} " =~ ' syslinux ' ]]; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating '${bootmode}': The 'syslinux' package is missing from the package list!" 0
    fi

    # Check if syslinux configuration files exist
    if [[ ! -d "${profile}/syslinux" ]]; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating '${bootmode}': The '${profile}/syslinux' directory is missing!" 0
    else
        local cfgfile
        for cfgfile in "${profile}/syslinux/"*'.cfg'; do
            if [[ -e "${cfgfile}" ]]; then
                break
            else
                (( validation_error=validation_error+1 ))
                _msg_error "Validating '${bootmode}': No configuration file found in '${profile}/syslinux/'!" 0
            fi
        done
    fi

    # Check for optional packages
    # shellcheck disable=SC2076
    if [[ ! " ${pkg_list[*]} " =~ ' memtest86+ ' ]]; then
        _msg_info "Validating '${bootmode}': 'memtest86+' is not in the package list. Memmory testing will not be available from syslinux."
    fi
}

_validate_requirements_bootmode_bios.syslinux.eltorito() {
    # bios.syslinux.eltorito has the exact same requirements as bios.syslinux.mbr
    _validate_requirements_bootmode_bios.syslinux.mbr
}

_validate_requirements_common_systemd-boot() {
    # Check if mkfs.fat is available
    if ! command -v mkfs.fat &>/dev/null; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating '${bootmode}': mkfs.fat is not available on this host. Install 'dosfstools'!" 0
    fi

    # Check if mmd and mcopy are available
    if ! { command -v mmd &>/dev/null && command -v mcopy &>/dev/null; }; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating '${bootmode}': mmd and/or mcopy are not available on this host. Install 'mtools'!" 0
    fi

    # Check if systemd-boot configuration files exist
    if [[ ! -d "${profile}/efiboot/loader/entries" ]]; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating '${bootmode}': The '${profile}/efiboot/loader/entries' directory is missing!" 0
    else
        if [[ ! -e "${profile}/efiboot/loader/loader.conf" ]]; then
            (( validation_error=validation_error+1 ))
            _msg_error "Validating '${bootmode}': File '${profile}/efiboot/loader/loader.conf' not found!" 0
        fi
        local conffile
        for conffile in "${profile}/efiboot/loader/entries/"*'.conf'; do
            if [[ -e "${conffile}" ]]; then
                break
            else
                (( validation_error=validation_error+1 ))
                _msg_error "Validating '${bootmode}': No configuration file found in '${profile}/efiboot/loader/entries/'!" 0
            fi
        done
    fi

    # Check for optional packages
    # shellcheck disable=SC2076
    if [[ ! " ${pkg_list[*]} " =~ ' edk2-shell ' ]]; then
        _msg_info "'edk2-shell' is not in the package list. The ISO will not contain a bootable UEFI shell."
    fi
}

_validate_requirements_bootmode_uefi-x64.systemd-boot.esp() {
    # shellcheck disable=SC2076
    if [[ " ${bootmodes[*]} " =~ ' uefi-x64.grub.esp ' ]]; then
        _msg_error "Validating '${bootmode}': cannot be used with bootmode uefi-x64.grub.esp!" 0
    fi
    _validate_requirements_common_systemd-boot
}

_validate_requirements_bootmode_uefi-x64.systemd-boot.eltorito() {
    # shellcheck disable=SC2076
    if [[ " ${bootmodes[*]} " =~ ' uefi-x64.grub.eltorito ' ]]; then
        _msg_error "Validating '${bootmode}': cannot be used with bootmode uefi-x64.grub.eltorito!" 0
    fi

    # uefi-x64.systemd-boot.eltorito has the exact same requirements as uefi-x64.systemd-boot.esp
    _validate_requirements_bootmode_uefi-x64.systemd-boot.esp
}

_validate_requirements_bootmode_uefi-ia32.systemd-boot.esp() {
    # shellcheck disable=SC2076
    if [[ " ${bootmodes[*]} " =~ ' uefi-ia32.grub.esp ' ]]; then
        _msg_error "Validating '${bootmode}': cannot be used with bootmode uefi-ia32.grub.esp!" 0
    fi

    _validate_requirements_common_systemd-boot
}

_validate_requirements_bootmode_uefi-ia32.systemd-boot.eltorito() {
    # shellcheck disable=SC2076
    if [[ " ${bootmodes[*]} " =~ ' uefi-ia32.grub.eltorito ' ]]; then
        _msg_error "Validating '${bootmode}': cannot be used with bootmode uefi-ia32.grub.eltorito!" 0
    fi

    # uefi-ia32.systemd-boot.eltorito has the exact same requirements as uefi-ia32.systemd-boot.esp
    _validate_requirements_bootmode_uefi-x64.systemd-boot.esp
}

_validate_requirements_bootmode_uefi-ia32.grub.esp() {
    # Check if GRUB is available
    if ! command -v grub-mkstandalone &>/dev/null; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating '${bootmode}': grub-install is not available on this host. Install 'grub'!" 0
    fi

    # shellcheck disable=SC2076
    if [[ " ${bootmodes[*]} " =~ ' uefi-x64.systemd-boot.esp ' ]]; then
        _validate_requirements_bootmode_uefi-x64.systemd-boot.esp
    elif [[ " ${bootmodes[*]} " =~ ' uefi-x64.grub.esp ' ]]; then
        _validate_requirements_bootmode_uefi-x64.grub.esp
    else
        _msg_error "Validating '${bootmode}': requires one of bootmode uefi-x64.systemd-boot.esp or uefi-x64.grub.esp" 0
    fi
}

_validate_requirements_bootmode_uefi-ia32.grub.eltorito() {
    # uefi-ia32.grub.eltorito has the exact same requirements as uefi-ia32.grub.esp
    _validate_requirements_bootmode_uefi-ia32.grub.esp
}

_validate_requirements_bootmode_uefi-x64.grub.esp() {
    # shellcheck disable=SC2076
    if [[ " ${bootmodes[*]} " =~ ' uefi-x64.systemd-boot.esp ' ]]; then
        _msg_error "Validating '${bootmode}': cannot be used with bootmode uefi-x64.systemd-boot.esp!" 0
    fi

    # Check if GRUB is available
    if ! command -v grub-mkstandalone &>/dev/null; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating '${bootmode}': grub-install is not available on this host. Install 'grub'!" 0
    fi

        # Check if mkfs.fat is available
    if ! command -v mkfs.fat &>/dev/null; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating '${bootmode}': mkfs.fat is not available on this host. Install 'dosfstools'!" 0
    fi

    # Check if mmd and mcopy are available
    if ! { command -v mmd &>/dev/null && command -v mcopy &>/dev/null; }; then
        _msg_error "Validating '${bootmode}': mmd and/or mcopy are not available on this host. Install 'mtools'!" 0
    fi

    # Check if GRUB configuration files exist
    if [[ ! -d "${profile}/grub" ]]; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating '${bootmode}': The '${profile}/grub' directory is missing!" 0
    else
        if [[ ! -e "${profile}/grub/grub.cfg" ]]; then
            (( validation_error=validation_error+1 ))
            _msg_error "Validating '${bootmode}': File '${profile}/grub/grub.cfg' not found!" 0
        fi
        local conffile
        for conffile in "${profile}/grub/"*'.cfg'; do
            if [[ -e "${conffile}" ]]; then
                break
            else
                (( validation_error=validation_error+1 ))
                _msg_error "Validating '${bootmode}': No configuration file found in '${profile}/grub/'!" 0
            fi
        done
    fi

    # Check for optional packages
    # shellcheck disable=SC2076
    if [[ ! " ${pkg_list[*]} " =~ ' edk2-shell ' ]]; then
        _msg_info "'edk2-shell' is not in the package list. The ISO will not contain a bootable UEFI shell."
    fi
    # shellcheck disable=SC2076
    if [[ ! " ${pkg_list[*]} " =~ ' memtest86+-efi ' ]]; then
        _msg_info "Validating '${bootmode}': 'memtest86+-efi' is not in the package list. Memory testing will not be available from GRUB."
    fi
}

_validate_requirements_bootmode_uefi-x64.grub.eltorito() {
    # shellcheck disable=SC2076
    if [[ " ${bootmodes[*]} " =~ ' uefi-x64.systemd-boot.eltorito ' ]]; then
        _msg_error "Validating '${bootmode}': cannot be used with bootmode uefi-x64.systemd-boot.eltorito!" 0
    fi
    # uefi-x64.grub.eltorito has the exact same requirements as uefi-x64.grub.esp
    _validate_requirements_bootmode_uefi-x64.grub.esp
}

# Build airootfs filesystem image
_prepare_airootfs_image() {
    _run_once "_mkairootfs_${airootfs_image_type}"
    _mkchecksum

    if [[ -e "${isofs_dir}/${install_dir}/${arch}/airootfs.sfs" ]]; then
        airootfs_image_filename="${isofs_dir}/${install_dir}/${arch}/airootfs.sfs"
    elif [[ -e "${isofs_dir}/${install_dir}/${arch}/airootfs.erofs" ]]; then
        airootfs_image_filename="${isofs_dir}/${install_dir}/${arch}/airootfs.erofs"
    fi

    if [[ -n "${gpg_key}" ]]; then
        _mk_pgp_signature "${airootfs_image_filename}"
    fi
    if [[ -v cert_list ]]; then
        _cms_sign_artifact "${airootfs_image_filename}"
    fi
}

# export build artifacts for netboot
_export_netboot_artifacts() {
    _msg_info "Exporting netboot artifacts..."
    install -d -m 0755 "${out_dir}"
    cp -a -- "${isofs_dir}/${install_dir}/" "${out_dir}/"

    # Remove grubenv since it serves no purpose in netboot artifacts
    rm -f -- "${out_dir}/${install_dir}/grubenv"

    _msg_info "Done!"
    du -hs -- "${out_dir}/${install_dir}"
}

_cms_sign_artifact() {
    local artifact="${1}"
    local openssl_flags=(
        "-sign"
        "-binary"
        "-nocerts"
        "-noattr"
        "-outform" "DER" "-out" "${artifact}.cms.sig"
        "-in" "${artifact}"
        "-signer" "${cert_list[0]}"
        "-inkey" "${cert_list[1]}"
    )

    if (( ${#cert_list[@]} > 2 )); then
        openssl_flags+=("-certfile" "${cert_list[2]}")
    fi

    _msg_info "Signing ${artifact} image using openssl cms..."

    rm -f -- "${artifact}.cms.sig"

    openssl cms "${openssl_flags[@]}"

    _msg_info "Done!"
}

# sign build artifacts for netboot
_sign_netboot_artifacts() {
    local _file _dir
    local _files_to_sign=()
    _msg_info "Signing netboot artifacts..."
    _dir="${isofs_dir}/${install_dir}/boot/"
    for _file in "${ucodes[@]}"; do
        if [[ -e "${_dir}${_file}" ]]; then
            _files_to_sign+=("${_dir}${_file}")
        fi
    done
    for _file in "${_files_to_sign[@]}" "${_dir}${arch}/vmlinuz-"!(*.sig) "${_dir}${arch}/initramfs-"*.img; do
        rm -f -- "${_file}".ipxe.sig
        openssl cms \
            -sign \
            -binary \
            -noattr \
            -in "${_file}" \
            -signer "${cert_list[0]}" \
            -inkey "${cert_list[1]}" \
            -outform DER \
            -out "${_file}".ipxe.sig
    done
    _msg_info "Done!"
}

_validate_requirements_airootfs_image_type_squashfs() {
    if ! command -v mksquashfs &>/dev/null; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating '${airootfs_image_type}': mksquashfs is not available on this host. Install 'squashfs-tools'!" 0
    fi
}

_validate_requirements_airootfs_image_type_ext4+squashfs() {
    if ! { command -v mkfs.ext4 &>/dev/null && command -v tune2fs &>/dev/null; }; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating '${airootfs_image_type}': mkfs.ext4 and/or tune2fs is not available on this host. Install 'e2fsprogs'!" 0
    fi
    _validate_requirements_airootfs_image_type_squashfs
}

_validate_requirements_airootfs_image_type_erofs() {
    if ! command -v mkfs.erofs &>/dev/null; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating '${airootfs_image_type}': mkfs.erofs is not available on this host. Install 'erofs-utils'!" 0
    fi
}

_validate_common_requirements_buildmode_all() {
    if ! command -v pacman &>/dev/null; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating build mode '${_buildmode}': pacman is not available on this host. Install 'pacman'!" 0
    fi
    if ! command -v find &>/dev/null; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating build mode '${_buildmode}': find is not available on this host. Install 'findutils'!" 0
    fi
    if ! command -v gzip &>/dev/null; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating build mode '${_buildmode}': gzip is not available on this host. Install 'gzip'!" 0
    fi
}

_validate_requirements_buildmode_bootstrap() {
    local bootstrap_pkg_list_from_file=()

    # Check if packages for the bootstrap image are specified
    if [[ -e "${bootstrap_packages}" ]]; then
        mapfile -t bootstrap_pkg_list_from_file < \
            <(sed '/^[[:blank:]]*#.*/d;s/#.*//;/^[[:blank:]]*$/d' "${bootstrap_packages}")
        bootstrap_pkg_list+=("${bootstrap_pkg_list_from_file[@]}")
        if (( ${#bootstrap_pkg_list_from_file[@]} < 1 )); then
            (( validation_error=validation_error+1 ))
            _msg_error "No package specified in '${bootstrap_packages}'." 0
        fi
    else
        (( validation_error=validation_error+1 ))
        _msg_error "Bootstrap packages file '${bootstrap_packages}' does not exist." 0
    fi

    _validate_common_requirements_buildmode_all
    if ! command -v bsdtar &>/dev/null; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating build mode '${_buildmode}': bsdtar is not available on this host. Install 'libarchive'!" 0
    fi
}

_validate_common_requirements_buildmode_iso_netboot() {
    local bootmode
    local pkg_list_from_file=()

    # Check if the package list file exists and read packages from it
    if [[ -e "${packages}" ]]; then
        mapfile -t pkg_list_from_file < <(sed '/^[[:blank:]]*#.*/d;s/#.*//;/^[[:blank:]]*$/d' "${packages}")
        pkg_list+=("${pkg_list_from_file[@]}")
        if (( ${#pkg_list_from_file[@]} < 1 )); then
            (( validation_error=validation_error+1 ))
            _msg_error "No package specified in '${packages}'." 0
        fi
    else
        (( validation_error=validation_error+1 ))
        _msg_error "Packages file '${packages}' does not exist." 0
    fi

    if [[ -v cert_list ]]; then
        # Check if the certificate files exist
        for _cert in "${cert_list[@]}"; do
            if [[ ! -e "${_cert}" ]]; then
                (( validation_error=validation_error+1 ))
                _msg_error "File '${_cert}' does not exist." 0
            fi
        done
        # Check if there are at least three certificate files to sign netboot and rootfs.
        if (( ${#cert_list[@]} < 2 )); then
            (( validation_error=validation_error+1 ))
            _msg_error "Two certificates are required for codesigning netboot artifacts, but '${cert_list[*]}' is provided." 0
        fi

        if ! command -v openssl &>/dev/null; then
            (( validation_error=validation_error+1 ))
            _msg_error "Validating build mode '${_buildmode}': openssl is not available on this host. Install 'openssl'!" 0
        fi
    fi

    # Check if the specified airootfs_image_type is supported
    if typeset -f "_mkairootfs_${airootfs_image_type}" &>/dev/null; then
        if typeset -f "_validate_requirements_airootfs_image_type_${airootfs_image_type}" &>/dev/null; then
            "_validate_requirements_airootfs_image_type_${airootfs_image_type}"
        else
            _msg_warning "Function '_validate_requirements_airootfs_image_type_${airootfs_image_type}' does not exist. Validating the requirements of '${airootfs_image_type}' airootfs image type will not be possible."
        fi
    else
        (( validation_error=validation_error+1 ))
        _msg_error "Unsupported image type: '${airootfs_image_type}'" 0
    fi
}

_validate_requirements_buildmode_iso() {
    _validate_common_requirements_buildmode_iso_netboot
    _validate_common_requirements_buildmode_all
    # Check if the specified bootmodes are supported
    if (( ${#bootmodes[@]} < 1 )); then
        (( validation_error=validation_error+1 ))
        _msg_error "No boot modes specified in '${profile}/profiledef.sh'." 0
    fi
    for bootmode in "${bootmodes[@]}"; do
        if typeset -f "_make_bootmode_${bootmode}" &>/dev/null; then
            if typeset -f "_validate_requirements_bootmode_${bootmode}" &>/dev/null; then
                "_validate_requirements_bootmode_${bootmode}"
            else
                _msg_warning "Function '_validate_requirements_bootmode_${bootmode}' does not exist. Validating the requirements of '${bootmode}' boot mode will not be possible."
            fi
        else
            (( validation_error=validation_error+1 ))
            _msg_error "${bootmode} is not a valid boot mode!" 0
        fi
    done

    if ! command -v awk &>/dev/null; then
        (( validation_error=validation_error+1 ))
        _msg_error "Validating build mode '${_buildmode}': awk is not available on this host. Install 'awk'!" 0
    fi
}

_validate_requirements_buildmode_netboot() {
    _validate_common_requirements_buildmode_iso_netboot
    _validate_common_requirements_buildmode_all
}

# SYSLINUX El Torito
_add_xorrisofs_options_bios.syslinux.eltorito() {
    xorrisofs_options+=(
        # El Torito boot image for x86 BIOS
        '-eltorito-boot' 'boot/syslinux/isolinux.bin'
        # El Torito boot catalog file
        '-eltorito-catalog' 'boot/syslinux/boot.cat'
        # Required options to boot with ISOLINUX
        '-no-emul-boot' '-boot-load-size' '4' '-boot-info-table'
    )
}

# SYSLINUX MBR (isohybrid)
_add_xorrisofs_options_bios.syslinux.mbr() {
    xorrisofs_options+=(
        # SYSLINUX MBR bootstrap code; does not work without "-eltorito-boot syslinux/isolinux.bin"
        '-isohybrid-mbr' "${isofs_dir}/boot/syslinux/isohdpfx.bin"
        # When GPT is used, create an additional partition in the MBR (besides 0xEE) for sectors 0–1 (MBR
        # bootstrap code area) and mark it as bootable
        # May allow booting on some systems
        # https://wiki.archlinux.org/title/Partitioning#Tricking_old_BIOS_into_booting_from_GPT
        '--mbr-force-bootable'
        # Move the first partition away from the start of the ISO to match the expectations of partition editors
        # May allow booting on some systems
        # https://dev.lovelyhq.com/libburnia/libisoburn/src/branch/master/doc/partition_offset.wiki
        '-partition_offset' '16'
    )
}

# GRUB in an attached EFI system partition
_add_xorrisofs_options_uefi-ia32.grub.esp() {
    # TODO: how does the bootmodes systemd-boot vs x64.grub affect ${bootmodes[*]} tests in _add_xorrisofs_options_uefi-x64.systemd-boot.esp etc?
    # shellcheck disable=SC2076
    if [[ ! " ${bootmodes[*]} " =~ ' uefi-x64.systemd-boot.esp ' && ! " ${bootmodes[*]} " =~ ' uefi-x64.grub.esp ' ]]; then
        # _add_xorrisofs_options_uefi-x64.systemd-boot.esp
        _add_xorrisofs_options_uefi-x64.grub.esp
    fi
}

# GRUB via El Torito
_add_xorrisofs_options_uefi-ia32.grub.eltorito() {
    # shellcheck disable=SC2076
    if [[ ! " ${bootmodes[*]} " =~ ' uefi-x64.systemd-boot.eltorito ' && ! " ${bootmodes[*]} " =~ ' uefi-x64.grub.eltorito ' ]]; then
        # _add_xorrisofs_options_uefi-x64.systemd-boot.eltorito
        _add_xorrisofs_options_uefi-x64.grub.eltorito
    fi
}

# systemd-boot in an attached EFI system partition
_add_xorrisofs_options_uefi-x64.systemd-boot.esp() {
    # Move the first partition away from the start of the ISO, otherwise the GPT will not be valid and ISO 9660
    # partition will not be mountable
    # shellcheck disable=SC2076
    [[ " ${xorrisofs_options[*]} " =~ ' -partition_offset ' ]] || xorrisofs_options+=('-partition_offset' '16')
    # Attach efiboot.img as a second partition and set its partition type to "EFI system partition"
    xorrisofs_options+=('-append_partition' '2' 'C12A7328-F81F-11D2-BA4B-00A0C93EC93B' "${efibootimg}")
    # Ensure GPT is used as some systems do not support UEFI booting without it
    # shellcheck disable=SC2076
    if [[ " ${bootmodes[*]} " =~ ' bios.syslinux.mbr ' ]]; then
        # A valid GPT prevents BIOS booting on some systems, instead use an invalid GPT (without a protective MBR).
        # The attached partition will have the EFI system partition type code in MBR, but in the invalid GPT it will
        # have a Microsoft basic partition type code.
        if [[ ! " ${bootmodes[*]} " =~ ' uefi-x64.systemd-boot.eltorito ' && ! " ${bootmodes[*]} " =~ ' uefi-ia32.grub.eltorito ' ]]; then
            # If '-isohybrid-gpt-basdat' is specified before '-e', then the appended EFI system partition will have the
            # EFI system partition type ID/GUID in both MBR and GPT. If '-isohybrid-gpt-basdat' is specified after '-e',
            # the appended EFI system partition will have the Microsoft basic data type GUID in GPT.
            if [[ ! " ${xorrisofs_options[*]} " =~ ' -isohybrid-gpt-basdat ' ]]; then
                xorrisofs_options+=('-isohybrid-gpt-basdat')
            fi
        fi
    else
        # Use valid GPT if BIOS booting support will not be required
        xorrisofs_options+=('-appended_part_as_gpt')
    fi
}

# systemd-boot via El Torito
_add_xorrisofs_options_uefi-x64.systemd-boot.eltorito() {
    # shellcheck disable=SC2076
    if [[ " ${bootmodes[*]} " =~ ' uefi-x64.systemd-boot.esp ' || " ${bootmodes[*]} " =~ ' uefi-ia32.grub.esp ' ]]; then
        # systemd-boot in an attached EFI system partition via El Torito
        xorrisofs_options+=(
            # Start a new El Torito boot entry for UEFI
            '-eltorito-alt-boot'
            # Set the second partition as the El Torito UEFI boot image
            '-e' '--interval:appended_partition_2:all::'
            # Boot image is not emulating floppy or hard disk; required for all known boot loaders
            '-no-emul-boot'
        )
        # A valid GPT prevents BIOS booting on some systems, use an invalid GPT instead.
        if [[ " ${bootmodes[*]} " =~ ' bios.syslinux.mbr ' ]]; then
            # If '-isohybrid-gpt-basdat' is specified before '-e', then the appended EFI system partition will have the
            # EFI system partition type ID/GUID in both MBR and GPT. If '-isohybrid-gpt-basdat' is specified after '-e',
            # the appended EFI system partition will have the Microsoft basic data type GUID in GPT.
            if [[ ! " ${xorrisofs_options[*]} " =~ ' -isohybrid-gpt-basdat ' ]]; then
                xorrisofs_options+=('-isohybrid-gpt-basdat')
            fi
        fi
    else
        # The ISO will not contain a GPT partition table, so to be able to reference efiboot.img, place it as a
        # file inside the ISO 9660 file system
        install -d -m 0755 -- "${isofs_dir}/EFI/archiso"
        cp -a -- "${efibootimg}" "${isofs_dir}/EFI/archiso/efiboot.img"
        # systemd-boot in an embedded efiboot.img via El Torito
        xorrisofs_options+=(
            # Start a new El Torito boot entry for UEFI
            '-eltorito-alt-boot'
            # Set efiboot.img as the El Torito UEFI boot image
            '-e' 'EFI/archiso/efiboot.img'
            # Boot image is not emulating floppy or hard disk; required for all known boot loaders
            '-no-emul-boot'
        )
    fi
    # Specify where to save the El Torito boot catalog file in case it is not already set by bios.syslinux.eltorito
    # shellcheck disable=SC2076
    [[ " ${bootmodes[*]} " =~ ' bios.' ]] || xorrisofs_options+=('-eltorito-catalog' 'EFI/boot.cat')
}

# GRUB in an attached EFI system partition.
# Same as _add_xorrisofs_options_uefi-x64.systemd-boot.esp.
_add_xorrisofs_options_uefi-x64.grub.esp() {
    # Move the first partition away from the start of the ISO, otherwise the GPT will not be valid and ISO 9660
    # partition will not be mountable
    # shellcheck disable=SC2076
    [[ " ${xorrisofs_options[*]} " =~ ' -partition_offset ' ]] || xorrisofs_options+=('-partition_offset' '16')
    # Attach efiboot.img as a second partition and set its partition type to "EFI system partition"
    xorrisofs_options+=('-append_partition' '2' 'C12A7328-F81F-11D2-BA4B-00A0C93EC93B' "${efibootimg}")
    # Ensure GPT is used as some systems do not support UEFI booting without it
    # shellcheck disable=SC2076
    if [[ " ${bootmodes[*]} " =~ ' bios.syslinux.mbr ' ]]; then
        # A valid GPT prevents BIOS booting on some systems, instead use an invalid GPT (without a protective MBR).
        # The attached partition will have the EFI system partition type code in MBR, but in the invalid GPT it will
        # have a Microsoft basic partition type code.
        if [[ ! " ${bootmodes[*]} " =~ ' uefi-x64.grub.eltorito ' && ! " ${bootmodes[*]} " =~ ' uefi-ia32.grub.eltorito ' ]]; then
            # If '-isohybrid-gpt-basdat' is specified before '-e', then the appended EFI system partition will have the
            # EFI system partition type ID/GUID in both MBR and GPT. If '-isohybrid-gpt-basdat' is specified after '-e',
            # the appended EFI system partition will have the Microsoft basic data type GUID in GPT.
            if [[ ! " ${xorrisofs_options[*]} " =~ ' -isohybrid-gpt-basdat ' ]]; then
                xorrisofs_options+=('-isohybrid-gpt-basdat')
            fi
        fi
    else
        # Use valid GPT if BIOS booting support will not be required
        xorrisofs_options+=('-appended_part_as_gpt')
    fi
}

# GRUB via El Torito
# Same as _add_xorrisofs_options_uefi-x64.systemd-boot.eltorito.
_add_xorrisofs_options_uefi-x64.grub.eltorito() {
    # shellcheck disable=SC2076
    if [[ " ${bootmodes[*]} " =~ ' uefi-x64.grub.esp ' || " ${bootmodes[*]} " =~ ' uefi-ia32.grub.esp ' ]]; then
        # grub in an attached EFI system partition via El Torito
        xorrisofs_options+=(
            # Start a new El Torito boot entry for UEFI
            '-eltorito-alt-boot'
            # Set the second partition as the El Torito UEFI boot image
            '-e' '--interval:appended_partition_2:all::'
            # Boot image is not emulating floppy or hard disk; required for all known boot loaders
            '-no-emul-boot'
        )
        # A valid GPT prevents BIOS booting on some systems, use an invalid GPT instead.
        if [[ " ${bootmodes[*]} " =~ ' bios.syslinux.mbr ' ]]; then
            # If '-isohybrid-gpt-basdat' is specified before '-e', then the appended EFI system partition will have the
            # EFI system partition type ID/GUID in both MBR and GPT. If '-isohybrid-gpt-basdat' is specified after '-e',
            # the appended EFI system partition will have the Microsoft basic data type GUID in GPT.
            if [[ ! " ${xorrisofs_options[*]} " =~ ' -isohybrid-gpt-basdat ' ]]; then
                xorrisofs_options+=('-isohybrid-gpt-basdat')
            fi
        fi
    else
        # The ISO will not contain a GPT partition table, so to be able to reference efiboot.img, place it as a
        # file inside the ISO 9660 file system
        install -d -m 0755 -- "${isofs_dir}/EFI/archiso"
        cp -a -- "${efibootimg}" "${isofs_dir}/EFI/archiso/efiboot.img"
        # grub in an embedded efiboot.img via El Torito
        xorrisofs_options+=(
            # Start a new El Torito boot entry for UEFI
            '-eltorito-alt-boot'
            # Set efiboot.img as the El Torito UEFI boot image
            '-e' 'EFI/archiso/efiboot.img'
            # Boot image is not emulating floppy or hard disk; required for all known boot loaders
            '-no-emul-boot'
        )
    fi
    # Specify where to save the El Torito boot catalog file in case it is not already set by bios.syslinux.eltorito
    # shellcheck disable=SC2076
    [[ " ${bootmodes[*]} " =~ ' bios.' ]] || xorrisofs_options+=('-eltorito-catalog' 'EFI/boot.cat')
}

# Build bootstrap image
_build_bootstrap_image() {
    local _bootstrap_parent
    _bootstrap_parent="$(dirname -- "${pacstrap_dir}")"

    [[ -d "${out_dir}" ]] || install -d -- "${out_dir}"

    cd -- "${_bootstrap_parent}"

    _msg_info "Creating bootstrap image..."
    bsdtar -cf - "root.${arch}" | gzip -cn9 >"${out_dir}/${image_name}"
    _msg_info "Done!"
    du -h -- "${out_dir}/${image_name}"
    cd -- "${OLDPWD}"
}

# Build ISO
_build_iso_image() {
    local xorriso_options=() xorrisofs_options=()
    local bootmode

    [[ -d "${out_dir}" ]] || install -d -- "${out_dir}"

    # Do not read xorriso startup files to prevent interference and unintended behavior.
    # For it to work, -no_rc must be the first argument passed to xorriso.
    xorriso_options=('-no_rc')


    if [[ "${quiet}" == "y" ]]; then
        # The when xorriso is run in mkisofs compatibility mode (xorrisofs), the mkisofs option -quiet is interpreted
        # too late (e.g. messages about SOURCE_DATE_EPOCH still get shown).
        # Instead use native xorriso option to silence the output.
        xorriso_options+=('-report_about' 'SORRY')
    fi

    # Add required xorrisofs options for each boot mode
    for bootmode in "${bootmodes[@]}"; do
        typeset -f "_add_xorrisofs_options_${bootmode}" &>/dev/null && "_add_xorrisofs_options_${bootmode}"
    done

    rm -f -- "${out_dir}/${image_name}"
    _msg_info "Creating ISO image..."
    xorriso "${xorriso_options[@]}" -as mkisofs \
        -iso-level 3 \
        -full-iso9660-filenames \
        -joliet \
        -joliet-long \
        -rational-rock \
        -volid "${iso_label}" \
        -appid "${iso_application}" \
        -publisher "${iso_publisher}" \
        -preparer "prepared by ${app_name}" \
        "${xorrisofs_options[@]}" \
        -output "${out_dir}/${image_name}" \
        "${isofs_dir}/"
    _msg_info "Done!"
    du -h -- "${out_dir}/${image_name}"
}

# Read profile's values from profiledef.sh
_read_profile() {
    if [[ -z "${profile}" ]]; then
        _msg_error "No profile specified!" 1
    fi
    if [[ ! -d "${profile}" ]]; then
        _msg_error "Profile '${profile}' does not exist!" 1
    elif [[ ! -e "${profile}/profiledef.sh" ]]; then
        _msg_error "Profile '${profile}' is missing 'profiledef.sh'!" 1
    else
        cd -- "${profile}"

        # Source profile's variables
        # shellcheck source=configs/releng/profiledef.sh
        . "${profile}/profiledef.sh"

        # Resolve paths of files that are expected to reside in the profile's directory
        [[ -n "$arch" ]] || arch="$(uname -m)"
        [[ -n "$packages" ]] || packages="${profile}/packages.${arch}"
        packages="$(realpath -- "${packages}")"
        pacman_conf="$(realpath -- "${pacman_conf}")"

        # Resolve paths of files that may reside in the profile's directory
        if [[ -z "$bootstrap_packages" ]] && [[ -e "${profile}/bootstrap_packages.${arch}" ]]; then
            bootstrap_packages="${profile}/bootstrap_packages.${arch}"
            bootstrap_packages="$(realpath -- "${bootstrap_packages}")"
            pacman_conf="$(realpath -- "${pacman_conf}")"
        fi

        cd -- "${OLDPWD}"
    fi
}

# Validate set options
_validate_options() {
    local validation_error=0 _buildmode certfile

    _msg_info "Validating options..."

    # Check if pacman configuration file exists
    if [[ ! -e "${pacman_conf}" ]]; then
        (( validation_error=validation_error+1 ))
        _msg_error "File '${pacman_conf}' does not exist." 0
    fi

    # Check if the code signing certificate files exist
    for certfile in "${cert_list[@]}"; do
        if [[ ! -e "$certfile" ]]; then
            (( validation_error=validation_error+1 ))
            _msg_error "Code signing certificate '${certfile}' does not exist." 0
        fi
    done

    # Check if the specified buildmodes are supported
    for _buildmode in "${buildmodes[@]}"; do
        if typeset -f "_build_buildmode_${_buildmode}" &>/dev/null; then
            if typeset -f "_validate_requirements_buildmode_${_buildmode}" &>/dev/null; then
                "_validate_requirements_buildmode_${_buildmode}"
            else
                _msg_warning "Function '_validate_requirements_buildmode_${_buildmode}' does not exist. Validating the requirements of '${_buildmode}' build mode will not be possible."
            fi
        else
            (( validation_error=validation_error+1 ))
            _msg_error "${_buildmode} is not a valid build mode!" 0
        fi
    done

    if (( validation_error )); then
        _msg_error "${validation_error} errors were encountered while validating the profile. Aborting." 1
    fi
    _msg_info "Done!"
}

# Set defaults and, if present, overrides from mkarchiso command line option parameters
_set_overrides() {
    # Set variables that have command line overrides
    [[ ! -v override_buildmodes ]] || buildmodes=("${override_buildmodes[@]}")
    if (( ${#buildmodes[@]} < 1 )); then
        buildmodes+=('iso')
    fi
    if [[ -v override_work_dir ]]; then
        work_dir="$override_work_dir"
    elif [[ -z "$work_dir" ]]; then
        work_dir='./work'
    fi
    work_dir="$(realpath -- "$work_dir")"
    if [[ -v override_out_dir ]]; then
        out_dir="$override_out_dir"
    elif [[ -z "$out_dir" ]]; then
        out_dir='./out'
    fi
    out_dir="$(realpath -- "$out_dir")"
    if [[ -v override_pacman_conf ]]; then
        pacman_conf="$override_pacman_conf"
    elif [[ -z "$pacman_conf" ]]; then
        pacman_conf="/etc/pacman.conf"
    fi
    pacman_conf="$(realpath -- "$pacman_conf")"
    [[ ! -v override_pkg_list ]] || pkg_list+=("${override_pkg_list[@]}")
    # TODO: allow overriding bootstrap_pkg_list
    if [[ -v override_iso_label ]]; then
        iso_label="$override_iso_label"
    elif [[ -z "$iso_label" ]]; then
        iso_label="${app_name^^}"
    fi
    if [[ -v override_iso_publisher ]]; then
        iso_publisher="$override_iso_publisher"
    elif [[ -z "$iso_publisher" ]]; then
        iso_publisher="${app_name}"
    fi
    if [[ -v override_iso_application ]]; then
        iso_application="$override_iso_application"
    elif [[ -z "$iso_application" ]]; then
        iso_application="${app_name} iso"
    fi
    if [[ -v override_install_dir ]]; then
        install_dir="$override_install_dir"
    elif [[ -z "$install_dir" ]]; then
        install_dir="${app_name}"
    fi
    [[ ! -v override_gpg_key ]] || gpg_key="$override_gpg_key"
    [[ ! -v override_gpg_sender ]] || gpg_sender="$override_gpg_sender"
    [[ ! -v override_cert_list ]] || mapfile -t cert_list < <(realpath -- "${override_cert_list[@]}")
    if [[ -v override_quiet ]]; then
        quiet="$override_quiet"
    elif [[ -z "$quiet" ]]; then
        quiet="y"
    fi
    if [[ -v override_rm_work_dir ]]; then
        rm_work_dir="$override_rm_work_dir"
    fi

    # Set variables that do not have overrides
    [[ -n "$airootfs_image_type" ]] || airootfs_image_type="squashfs"
    [[ -n "$iso_name" ]] || iso_name="${app_name}"
    # Precalculate the ISO's modification date in UTC, i.e. its "UUID"
    TZ=UTC printf -v iso_uuid '%(%F-%H-%M-%S-00)T' "$SOURCE_DATE_EPOCH"
}

_export_gpg_publickey() {
    gpg_publickey="${work_dir}/pubkey.gpg"
    rm -f -- "$gpg_publickey"
    gpg --batch --no-armor --output "$gpg_publickey" --export "${gpg_key}"
    [[ -s "$gpg_publickey" ]] || return
}

_make_version() {
    local _os_release

    _msg_info "Creating version files..."
    # Write version file to system installation dir
    rm -f -- "${pacstrap_dir}/version"
    printf '%s\n' "${iso_version}" >"${pacstrap_dir}/version"

    if [[ "${buildmode}" == @("iso"|"netboot") ]]; then
        install -d -m 0755 -- "${isofs_dir}/${install_dir}"
        # Write version file to ISO 9660
        printf '%s\n' "${iso_version}" >"${isofs_dir}/${install_dir}/version"

    fi
    if [[ "${buildmode}" == "iso" ]]; then
        # Write grubenv with version information to ISO 9660
        # TODO: after sufficient time has passed, do not create this file anymore when GRUB boot modes are used.
        #       _make_common_bootmode_grub_cfg already creates ${isofs_dir}/boot/grub/grubenv
        rm -f -- "${isofs_dir}/${install_dir}/grubenv"
        printf '%.1024s' "$(printf '# GRUB Environment Block\nNAME=%s\nVERSION=%s\n%s' \
            "${iso_name}" "${iso_version}" "$(printf '%0.1s' "#"{1..1024})")" \
            >"${isofs_dir}/${install_dir}/grubenv"
    fi

    # Append IMAGE_ID & IMAGE_VERSION to os-release
    _os_release="$(realpath -- "${pacstrap_dir}/etc/os-release")"
    if [[ ! -e "${pacstrap_dir}/etc/os-release" && -e "${pacstrap_dir}/usr/lib/os-release" ]]; then
        _os_release="$(realpath -- "${pacstrap_dir}/usr/lib/os-release")"
    fi
    if [[ "${_os_release}" != "${pacstrap_dir}"* ]]; then
        _msg_warning "os-release file '${_os_release}' is outside of valid path."
    else
        [[ ! -e "${_os_release}" ]] || sed -i '/^IMAGE_ID=/d;/^IMAGE_VERSION=/d' "${_os_release}"
        printf 'IMAGE_ID=%s\nIMAGE_VERSION=%s\n' "${iso_name}" "${iso_version}" >>"${_os_release}"
    fi

    # Touch /usr/lib/clock-epoch to give another hint on date and time
    # for systems with screwed or broken RTC.
    touch -m -d"@${SOURCE_DATE_EPOCH}" -- "${pacstrap_dir}/usr/lib/clock-epoch"

    _msg_info "Done!"
}

_make_pkglist() {
    _msg_info "Creating a list of installed packages on live-enviroment..."
    case "${buildmode}" in
        "bootstrap")
            pacman -Q --sysroot "${pacstrap_dir}" >"${pacstrap_dir}/pkglist.${arch}.txt"
            ;;
        "iso"|"netboot")
            install -d -m 0755 -- "${isofs_dir}/${install_dir}"
            pacman -Q --sysroot "${pacstrap_dir}" >"${isofs_dir}/${install_dir}/pkglist.${arch}.txt"
            ;;
    esac
    _msg_info "Done!"
}

# Create working directory
_make_work_dir() {
    if [[ ! -d "${work_dir}" ]]; then
        install -d -- "${work_dir}"
    elif (( rm_work_dir )); then
        rm_work_dir=0
        _msg_warning "Working directory removal requested, but '${work_dir}' already exists. It will not be removed!" 0
    fi
}

# build the base for an ISO and/or a netboot target
_build_iso_base() {
    local run_once_mode="base"
    local buildmode_packages="${packages}"
    # Set the package list to use
    local buildmode_pkg_list=("${pkg_list[@]}")
    # Set up essential directory paths
    pacstrap_dir="${work_dir}/${arch}/airootfs"
    isofs_dir="${work_dir}/iso"

    # Create working directory
    _run_once _make_work_dir
    # Write build date to file if it does not exist already
    [[ -e "${work_dir}/build_date" ]] || printf '%s\n' "$SOURCE_DATE_EPOCH" >"${work_dir}/build_date"

    [[ "${quiet}" == "y" ]] || _show_config
    _run_once _make_pacman_conf
    [[ -z "${gpg_key}" ]] || _run_once _export_gpg_publickey
    _run_once _make_custom_airootfs
    _run_once _make_packages
    _run_once _make_version
    _run_once _make_customize_airootfs
    _run_once _make_pkglist
    if [[ "${buildmode}" == 'netboot' ]]; then
        _run_once _make_boot_on_iso9660
    else
        _make_bootmodes
    fi
    _run_once _cleanup_pacstrap_dir
    _run_once _prepare_airootfs_image
}

# Build the bootstrap buildmode
_build_buildmode_bootstrap() {
    local image_name="${iso_name}-bootstrap-${iso_version}-${arch}.tar.gz"
    local run_once_mode="${buildmode}"
    local buildmode_packages="${bootstrap_packages}"
    # Set the package list to use
    local buildmode_pkg_list=("${bootstrap_pkg_list[@]}")

    # Set up essential directory paths
    pacstrap_dir="${work_dir}/${arch}/bootstrap/root.${arch}"
    [[ -d "${work_dir}" ]] || install -d -- "${work_dir}"
    install -d -m 0755 -o 0 -g 0 -- "${pacstrap_dir}"

    [[ "${quiet}" == "y" ]] || _show_config
    _run_once _make_pacman_conf
    _run_once _make_packages
    _run_once _make_version
    _run_once _make_pkglist
    _run_once _cleanup_pacstrap_dir
    _run_once _build_bootstrap_image
}

# Build the netboot buildmode
_build_buildmode_netboot() {
    local run_once_mode="${buildmode}"

    _build_iso_base

    if [[ -e "${isofs_dir}/${install_dir}/${arch}/airootfs.sfs" ]]; then
        airootfs_image_filename="${isofs_dir}/${install_dir}/${arch}/airootfs.sfs"
    elif [[ -e "${isofs_dir}/${install_dir}/${arch}/airootfs.erofs" ]]; then
        airootfs_image_filename="${isofs_dir}/${install_dir}/${arch}/airootfs.erofs"
    fi

    if [[ -v cert_list ]]; then
        _run_once _sign_netboot_artifacts
    fi
    _run_once _export_netboot_artifacts
}

# Build the ISO buildmode
_build_buildmode_iso() {
    local image_name="${iso_name}-${iso_version}-${arch}.iso"
    local run_once_mode="${buildmode}"
    efibootimg="${work_dir}/efiboot.img"
    _build_iso_base
    _run_once _build_iso_image
}

# build all buildmodes
_build() {
    local buildmode
    local run_once_mode="build"

    for buildmode in "${buildmodes[@]}"; do
        _run_once "_build_buildmode_${buildmode}"
    done
    if (( rm_work_dir )); then
        _msg_info 'Removing the working directory...'
        rm -rf -- "${work_dir:?}/"
        _msg_info 'Done!'
    fi
}

while getopts 'c:p:C:L:P:A:D:w:m:o:g:G:vrh?' arg; do
    case "${arg}" in
        p) read -r -a override_pkg_list <<<"${OPTARG}" ;;
        C) override_pacman_conf="${OPTARG}" ;;
        L) override_iso_label="${OPTARG}" ;;
        P) override_iso_publisher="${OPTARG}" ;;
        A) override_iso_application="${OPTARG}" ;;
        D) override_install_dir="${OPTARG}" ;;
        c) read -r -a override_cert_list <<<"${OPTARG}" ;;
        w) override_work_dir="${OPTARG}" ;;
        m) read -r -a override_buildmodes <<<"${OPTARG}" ;;
        o) override_out_dir="${OPTARG}" ;;
        g) override_gpg_key="${OPTARG}" ;;
        G) override_gpg_sender="${OPTARG}" ;;
        v) override_quiet="n" ;;
        r) declare -i override_rm_work_dir=1 ;;
        h|?) _usage 0 ;;
        *)
            _msg_error "Invalid argument '${arg}'" 0
            _usage 1
            ;;
    esac
done

shift $((OPTIND - 1))

if (( $# < 1 )); then
    _msg_error "No profile specified" 0
    _usage 1
fi

if (( EUID != 0 )); then
    _msg_error "${app_name} must be run as root." 1
fi

# get the absolute path representation of the first non-option argument
profile="$(realpath -- "${1}")"

# Read SOURCE_DATE_EPOCH from file early
build_date_file="$(realpath -q -- "${override_work_dir:-./work}/build_date")" || :
if [[ -f "$build_date_file" ]]; then
    SOURCE_DATE_EPOCH="$(<"$build_date_file")"
fi
unset build_date_file

_read_profile
_set_overrides
_validate_options
_build

# vim:ts=4:sw=4:et: