#!/bin/sh

# The builtin grub.cfg generator. This script is called by

# ostree/src/libostree/ostree-bootloader-grub2.c whenever boot loader

# configuration file needs to be updated on systems which do not use

# grub2-mkconfig (and thus, the `ostree admin instutil grub2-generate` path).

#

# It can be used as a template for a custom grub.cfg generator. What to consider

# when writing a custom grub.cfg generator:

#

#   - The populate_menu() function converts boot loader entries as defined by

#   https://www.freedesktop.org/wiki/Specifications/BootLoaderSpec/ into GRUB2

#   menuentry sections. This is the core logic that is required by OSTree

#   based system.

#

#   - Embedded systems: Be aware that this script is executed not only on a host machine by OS

#   installer, but also on a target device, thus think about shell portability. A target device

#   for example might be using busybox with a limited shell.

#

# Feel free to edit this script to fit your requirements.

set -e

script=$(basename ${0})

# Atomically safe location where to generete grub.cfg when executing system upgrade.

new_grub2_cfg=${2}

entries_path=$(dirname $new_grub2_cfg)/entries

read_config()

{

    config_file=${1}

    title=""

    initrd=""

    options=""

    linux=""

    devicetree=""

    while read -r line

    do

        record=$(echo ${line} | cut -f 1 -d ' ')

        value=$(echo ${line} | cut -s -f2- -d ' ')

        case "${record}" in

            "title")

                title=${value}

                ;;

            "initrd")

                initrd=${value}

                ;;

            "linux")

                linux=${value}

                ;;

            "devicetree")

                devicetree=${value}

                ;;

            "options")

                options=${value}

                ;;

        esac

    done < ${config_file}

    if [ -z "${title}" ]; then

        title="(Untitled)"

    fi

}

populate_menu()

{

    # Default to /boot if OSTREE_BOOT_PARTITION is not set and /boot is on the same device as /ostree/repo

    if [ -z ${OSTREE_BOOT_PARTITION+x} ] && [ -d /boot/ostree ] && [ -d /ostree/repo ] && [ $(stat -c '%d' /boot/ostree) -eq $(stat -c '%d' /ostree/repo) ]; then

        boot_prefix="/boot"

    else

        boot_prefix="${OSTREE_BOOT_PARTITION}"

    fi

    for config in $(ls -v -r $entries_path/*.conf); do

        read_config ${config}

        menu="${menu}menuentry '${title}' {\n"

        menu="${menu}\t linux ${boot_prefix}${linux} ${options}\n"

        if [ -n "${initrd}" ] ; then

            menu="${menu}\t initrd ${boot_prefix}${initrd}\n"

        fi

        if [ -n "${devicetree}" ] ; then

            menu="${menu}\t devicetree ${boot_prefix}${devicetree}\n"

        fi

        menu="${menu}}\n\n"

    done

    # The printf command seems to be more reliable across shells for special character (\n, \t) evaluation

    printf "$menu" >> ${new_grub2_cfg}

}

populate_warning()

{

cat >> ${new_grub2_cfg} <

# This file was generated by ${script}. Do not modify the generated file - all changes will

# be lost the next time file is regenerated. For more details refer to the ${script} script.

EOF

}

populate_header()

{

cat >> ${new_grub2_cfg} <

serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1

default=boot

timeout=10

EOF

}

generate_grub2_cfg()

{

    populate_warning

    populate_header

    populate_menu

}

generate_grub2_cfg