diskimage-builder/diskimage_builder/elements/bootloader/finalise.d/50-bootloader

#!/bin/bash

# Configure grub. Note that the various conditionals here are to handle
# different distributions gracefully.

if [ ${DIB_DEBUG_TRACE:-1} -gt 0 ]; then
    set -x
fi
set -eu
set -o pipefail

BOOT_DEV=$IMAGE_BLOCK_DEVICE

# All available devices, handy for some bootloaders...
declare -A DEVICES
eval DEVICES=( $IMAGE_BLOCK_DEVICES )

function install_extlinux {
    install-packages -m bootloader extlinux

    echo "Installing Extlinux..."

    # Find and install mbr.bin
    for MBR in /usr/share/syslinux/mbr.bin /usr/lib/syslinux/mbr.bin \
        /usr/lib/extlinux/mbr.bin /usr/lib/EXTLINUX/mbr.bin ; do
        if [ -f $MBR ]; then
            break
        fi
    done
    if [ ! -f $MBR ]; then
        echo "mbr.bin (from EXT/SYSLINUX) not found."
        exit 1
    fi

    dd if=$MBR of=$BOOT_DEV

    # Find any pre-created extlinux install directory
    for EXTDIR in /boot/extlinux /boot/syslinux ; do
        if [ -d $EXTDIR ] ; then
            break
        fi
    done
    if [ ! -d $EXTDIR ] ; then
        # No install directory found so default to /boot/syslinux
        EXTDIR=/boot/syslinux
        mkdir -p $EXTDIR
    fi

    # Finally install extlinux
    extlinux --install $EXTDIR
}

function install_grub2 {

    # Check for offline installation of grub
    if [ -f "/tmp/grub/install" ] ; then
        source /tmp/grub/install

    # Right now we can't use pkg-map to branch by arch, so tag an
    # architecture specific virtual package so we can install the
    # rigth thing based on distribution.
    elif [[ "$ARCH" =~ "ppc" ]]; then
        install-packages -m bootloader grub-ppc64
    elif [[ "${DIB_BLOCK_DEVICE}" == "mbr" ||
                "${DIB_BLOCK_DEVICE}" == "gpt" ]]; then
        install-packages -m bootloader grub-pc
    elif [[ "${DIB_BLOCK_DEVICE}" == "efi" ]]; then
        install-packages -e -m bootloader grub-efi-$ARCH
        install-packages -m bootloader grub-efi grub-efi-$ARCH
    else
        echo "Failure: I'm not sure what bootloader to install"
        echo "Ensure you have included a block-device-* element"
        exit 1
    fi

    # XXX: grub-probe on the nbd0/loop0 device returns nothing - workaround, manually
    # specify modules. https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1073731
    GRUBNAME=$(type -p grub-install) || echo "trying grub2-install"
    if [ -z "$GRUBNAME" ]; then
        GRUBNAME=$(type -p grub2-install)
    fi

    if type grub2-mkconfig >/dev/null; then
        GRUB_MKCONFIG="grub2-mkconfig"
    else
        GRUB_MKCONFIG="grub-mkconfig"
    fi

    # If no GRUB2 is found, fallback to extlinux
    if [ -z "$GRUBNAME" ] || [ $($GRUBNAME --version | grep "0.97" | wc -l) -ne 0 ]; then
        echo "No GRUB2 found. Fallback to Extlinux..."
        install_extlinux
        exit 0
    fi

    echo "Installing GRUB2..."

    # When using EFI image-based builds, particularly rhel element
    # based on RHEL>=8.2 .qcow2, we might have /boot/grub2/grubenv
    # as a dangling symlink to /boot/efi because we have extracted
    # it from the root fs, but we didn't populate the separate EFI
    # boot partition from the image.  grub2-install calls rename()
    # on this file, so if it's a dangling symlink it errors.  Just
    # remove it if it exists.
    if [[ -L /boot/grub2/grubenv ]]; then
        rm -f /boot/grub2/grubenv
    fi

    # We need --force so grub does not fail due to being installed on the
    # root partition of a block device.
    GRUB_OPTS=${GRUB_OPTS:-"--force"}
    # XXX: This is buggy:
    # - --target=i386-pc is invalid for non-i386/amd64 architectures
    # - and for UEFI too.
    #    GRUB_OPTS="$GRUB_OPTS --target=i386-pc"
    if [[ ! $GRUB_OPTS == *--target* ]] && [[ $($GRUBNAME --version) =~ ' 2.' ]]; then
        # /sys/ comes from the host machine. If the host machine is using EFI
        # but the image being built doesn't have EFI boot-images installed we
        # should set the --target to use a BIOS-based boot-image.
        #
        # * --target tells grub what's the target platform
        # * the boot images are placed in /usr/lib/grub/<cpu>-<platform>
        # * i386-pc is used for BIOS-based machines
        # http://www.gnu.org/software/grub/manual/grub.html#Installation
        #
        if [ -d /sys/firmware/efi ]; then
            if [ ! -d /usr/lib/grub/*-efi ]; then
                case $ARCH in
                    "x86_64"|"amd64")
                        GRUB_OPTS="$GRUB_OPTS --target=i386-pc"
                        ;;
                    "i386")
                        target=i386-pc
                        if [ -e /proc/device-tree ]; then
                            for x in /proc/device-tree/*; do
                                if [ -e "$x" ]; then
                                    target="i386-ieee1275"
                                fi
                            done
                        fi
                        GRUB_OPTS="$GRUB_OPTS --target=$target"
                        ;;
                esac
            fi
        fi
    fi

    if [[ "$ARCH" =~ "ppc" ]] ; then
        # For PPC (64-Bit regardless of Endian-ness), we use the "boot"
        # partition as the one to point grub-install to, not the loopback
        # device.  ppc has a dedicated PReP boot partition.
        # For grub2 < 2.02~beta3 this needs to be a /dev/mapper/... node after
        # that a dev/loopXpN node will work fine.
        $GRUBNAME --modules="part_msdos" $GRUB_OPTS ${DEVICES[boot]} --no-nvram
    else
        # This set of modules is sufficient for all installs (mbr/gpt/efi)
        modules="part_msdos part_gpt lvm"
        if [[ ${DIB_BLOCK_DEVICE} == "mbr" || ${DIB_BLOCK_DEVICE} == "gpt" ]]; then
            $GRUBNAME --modules="$modules biosdisk" $GRUB_OPTS $BOOT_DEV
        elif [[ ${DIB_BLOCK_DEVICE} == "efi" ]]; then
            # We need to manually set the target if it's different to
            # the host.  Setup for EFI
            case $ARCH in
                "x86_64"|"amd64")
                    # This call installs grub for BIOS compatability
                    # which makes portable EFI/BIOS images.
                    $GRUBNAME --modules="$modules" --target=i386-pc $BOOT_DEV
                    # Set the x86_64 specific efi target for the generic
                    # installation below.
                    GRUB_OPTS="--target=x86_64-efi"
                    ;;
                # At this point, we don't need to override the target
                # for any other architectures.
            esac
            # If we don't have a distro specific dir with presigned efi targets
            # we install a generic one.
            if [ ! -d /boot/efi/$EFI_BOOT_DIR ]; then
                echo "WARNING: /boot/efi/$EFI_BOOT_DIR does not exist, UEFI secure boot not supported"
                # This tells the EFI install to put the EFI binaries into
                # the generic /BOOT directory and avoids trying to update
                # nvram settings.
                extra_options="--removable"
                $GRUBNAME --modules="$modules" $extra_options $GRUB_OPTS $BOOT_DEV
            fi
        fi
    fi

    # This might be better factored out into a per-distro 'install-bootblock'
    # helper.
    if [ -d /boot/grub2 ]; then
        GRUB_CFG=/boot/grub2/grub.cfg
    elif [ -d /boot/grub ]; then
        GRUB_CFG=/boot/grub/grub.cfg
    fi

    # Override the root device to the default label, and disable uuid
    # lookup.
    echo "GRUB_DEVICE=LABEL=${DIB_ROOT_LABEL}" >> /etc/default/grub
    echo 'GRUB_DISABLE_LINUX_UUID=true' >> /etc/default/grub
    echo "GRUB_TIMEOUT=${DIB_GRUB_TIMEOUT:-5}" >>/etc/default/grub
    echo 'GRUB_TERMINAL="serial console"' >>/etc/default/grub
    echo 'GRUB_GFXPAYLOAD_LINUX=auto' >>/etc/default/grub

    # NOTE(ianw) : 2021-05-11
    # On Fedora there has been a switch to BLS
    #  https://fedoraproject.org/wiki/Changes/BootLoaderSpecByDefault
    # which means that kernel-install will have created entries in
    #  /boot/loader/entries/...
    # and, as the wiki page says
    #
    #   The main issue appears to be that a number of places document
    #   a way to pass kernel options that is no longer working with
    #   BLS, i.e. edit /etc/default/grub before running
    #   grub2-mkconfig.
    #
    # i.e. exactly what we're doing above to override the root device
    # in particular.  Override grub2 to use it's old config format and
    # remove any BLS entries the kernel install made.
    #
    # I imagine at some point we will reworking things in a more
    # general sense to support BLS if that's what everything is
    # switching to.
    #
    if [[ ${DISTRO_NAME} = fedora ]]; then
        echo 'GRUB_ENABLE_BLSCFG=false' >> /etc/default/grub
        rm -rf /boot/loader/
    fi

    if [[ -n "${DIB_BOOTLOADER_SERIAL_CONSOLE}" ]]; then
        SERIAL_CONSOLE="${DIB_BOOTLOADER_SERIAL_CONSOLE}"
    elif [[ "powerpc ppc64 ppc64le" =~ "$ARCH" ]]; then
        # Serial console on Power is hvc0
        SERIAL_CONSOLE="hvc0"
    elif [[ "arm64" =~ "$ARCH" ]]; then
        SERIAL_CONSOLE="ttyAMA0,115200"
    else
        SERIAL_CONSOLE="ttyS0,115200"
    fi

    GRUB_CMDLINE_LINUX_DEFAULT="console=tty0 console=${SERIAL_CONSOLE} no_timer_check"

    echo "GRUB_CMDLINE_LINUX_DEFAULT=\"${GRUB_CMDLINE_LINUX_DEFAULT} ${DIB_BOOTLOADER_DEFAULT_CMDLINE}\"" >>/etc/default/grub
    echo 'GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"' >>/etc/default/grub

    # os-prober leaks /dev/sda into config file in dual-boot host
    # Disable grub-os-prober to avoid the issue  while running
    # grub-mkconfig
    # Setting a flag to track whether the entry is already there in grub config
    PROBER_DISABLED=
    if ! grep -qe "^\s*GRUB_DISABLE_OS_PROBER=true" /etc/default/grub; then
        PROBER_DISABLED=true
        echo 'GRUB_DISABLE_OS_PROBER=true' >> /etc/default/grub
    fi

    # GRUB_MKCONFIG call needs to happen after we configure
    # /etc/default/grub above. Without this we can set inappropriate
    # root device labels and then images don't boot.
    #
    # This produces a legacy config which both bios and uefi can boot
    # Later we copy the final config to an efi specific location to
    # support uefi specific functionality like secure boot.
    $GRUB_MKCONFIG -o $GRUB_CFG

    # Remove the fix to disable os_prober
    if [ -n "$PROBER_DISABLED" ]; then
        sed -i '$d' /etc/default/grub
    fi

    # grub-mkconfig generates a config with the device in it,
    # This shouldn't be needed, but old code has bugs
    DIB_RELEASE=${DIB_RELEASE:-}
    if [ "$DIB_RELEASE" = 'wheezy' ]; then
        sed -i "s%search --no.*%%" $GRUB_CFG
        sed -i "s%set root=.*%set root=(hd0,1)%" $GRUB_CFG
    fi

    # Fix efi specific instructions in grub config file
    if [ -d /sys/firmware/efi ]; then
        sed -i 's%\(initrd\|linux\)efi /boot%\1 /boot%g' $GRUB_CFG
    fi

    # when using efi, and having linux16/initrd16, it needs to be replaced
    # by linuxefi/initrdefi. When building images on a non-efi system,
    # the 16 suffix is added to linux/initrd entries, but we need it to be
    # linuxefi/initrdefi for the image to boot under efi
    if [[ ${DIB_BLOCK_DEVICE} == "efi" ]]; then
        sed -i 's%\(linux\|initrd\)16 /boot%\1efi /boot%g' $GRUB_CFG

        # Finally copy the grub.cfg to the EFI specific dir to support
        # functionality like secure boot. We make a copy because
        # /boot and /boot/efi may be different partitions and uefi looks
        # for a specific partition UUID preventing symlinks from working.
        if [ -d /boot/efi/$EFI_BOOT_DIR ] ; then
            cp $GRUB_CFG /boot/efi/$EFI_BOOT_DIR/grub.cfg
        fi
    fi
}

DIB_EXTLINUX=${DIB_EXTLINUX:-0}
if [ "$DIB_EXTLINUX" != "0" ]; then
    install_extlinux
else
    install_grub2
fi