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

PART_DEV=$IMAGE_BLOCK_DEVICE
BOOT_DEV=$IMAGE_BLOCK_DEVICE_WITHOUT_PART

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
    elif [[ "$ARCH" =~ "ppc" ]]; then
        install-packages grub-ieee1275
    else
        install-packages -m bootloader grub-pc
    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=$(which grub-install) || echo "trying grub2-install"
    if [ -z "$GRUBNAME" ]; then
        GRUBNAME=$(which grub2-install)
    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..."

    # 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
        $GRUBNAME --modules="part_msdos" $GRUB_OPTS $BOOT_DEV --no-nvram
    else
        $GRUBNAME --modules="biosdisk part_msdos" $GRUB_OPTS $BOOT_DEV
    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=text' >>/etc/default/grub
    echo 'GRUB_CMDLINE_LINUX_DEFAULT="console=tty0 console=ttyS0,115200 no_timer_check"' >>/etc/default/grub
    echo 'GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"' >>/etc/default/grub
    if which grub2-mkconfig >/dev/null; then
        GRUB_MKCONFIG="grub2-mkconfig -o $GRUB_CFG"
    else
        GRUB_MKCONFIG="grub-mkconfig -o $GRUB_CFG"
    fi
    DISTRO_NAME=${DISTRO_NAME:-}
    case $DISTRO_NAME in
        'ubuntu'|'debian')
            sed -i -e "s/\(^GRUB_CMDLINE_LINUX.*\)\"$/\1 ${DIB_BOOTLOADER_DEFAULT_CMDLINE}\"/" /etc/default/grub
            GRUB_MKCONFIG=update-grub
        ;;
        'fedora'|'centos7'|'centos')
            echo "GRUB_CMDLINE_LINUX=\"${DIB_BOOTLOADER_DEFAULT_CMDLINE}\"" >>/etc/default/grub
        ;;
        'opensuse')
            sed -i -e "s/\(^GRUB_CMDLINE_LINUX.*\)\"$/\1 ${DIB_BOOTLOADER_DEFAULT_CMDLINE}\"/" /etc/default/grub
        ;;
    esac

    # 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

    # 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" = 'precise' ] || [ "$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
}

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