41_snapshots-btrfs

#! /usr/bin/env bash
#
# Written by: Antynea
# BTC donation address: 1Lbvz244WA8xbpHek9W2Y12cakM6rDe5Rt
# Github: https://github.com/Antynea/grub-btrfs
#
# Purpose:
#   Improves Grub by adding "btrfs snapshots" to the Grub menu.
#   You can boot your system on a "snapshot" from the Grub menu.
#   Supports manual snapshots, snapper, timeshift ...
#   Warning : booting on read-only snapshots can be tricky.
#   (Read about it, https://github.com/Antynea/grub-btrfs#warning-booting-on-read-only-snapshots-can-be-tricky)
#
# What this script does:
# - Automatically List snapshots existing on root partition (btrfs).
# - Automatically Detect if "/boot" is in separate partition.
# - Automatically Detect kernel, initramfs and intel/amd microcode in "/boot" directory on snapshots.
# - Automatically Create corresponding "menuentry" in grub.cfg.
# - Automatically detect the type/tags and descriptions/comments of snapper/timeshift snapshots.
# - Automatically generate grub.cfg if you use the provided systemd service.
#
# Installation:
# - Refer to https://github.com/Antynea/grub-btrfs#%EF%B8%8F-installation
#
# Customization:
#  You have the possibility to modify many parameters in /etc/default/grub-btrfs/config.
#  Read more here https://github.com/Antynea/grub-btrfs#installation- an in the manpage
#  'man grub-btrfs'
#
# Automatically update Grub
#  If you would like grub-btrfs menu to automatically update when a snapshot is created or deleted:
#  - Refer to https://github.com/Antynea/grub-btrfs#-automatically-update-grub-upon-snapshot.
#
# Special thanks for assistance and contributions:
# - My friends
# - All contributors on Github
#

set -e

sysconfdir="/etc"
grub_btrfs_config="${sysconfdir}/default/grub-btrfs/config"

[[ -f "$grub_btrfs_config" ]] && . "$grub_btrfs_config"
[[ -f "${sysconfdir}/default/grub" ]] && . "${sysconfdir}/default/grub"

## Error Handling
print_error()
{
    local err_msg="$*"
    local bug_report="If you think an error has occurred, please file a bug report at \"https://github.com/Antynea/grub-btrfs\""
    printf "%s\n" "${err_msg}" "${bug_report}" >&2 ;
    exit 0
}

# parse arguments
while getopts :V-: opt; do
    case "$opt" in
        -)
            case "${OPTARG}" in
                version)
                    printf "Version %s\n" "${GRUB_BTRFS_VERSION}" >&2 ;
                    exit 0
                    ;;
            esac;;
        V)
            printf "Version %s\n" "${GRUB_BTRFS_VERSION}" >&2 ;
            exit 0
            ;;
        *)
            printf "Unknown flag, exiting...\n"
            exit 0
            ;;
    esac
done

## Exit the script, if:
[[ "${GRUB_BTRFS_DISABLE,,}" == "true" ]] && print_error "GRUB_BTRFS_DISABLE is set to true (default=false)"
if ! type btrfs >/dev/null 2>&1; then print_error "btrfs-progs isn't installed"; fi
[[ -f "${GRUB_BTRFS_MKCONFIG_LIB:-/usr/share/grub/grub-mkconfig_lib}" ]] && . "${GRUB_BTRFS_MKCONFIG_LIB:-/usr/share/grub/grub-mkconfig_lib}" || print_error "grub-mkconfig_lib couldn't be found"
[[ "$(btrfs filesystem df / 2>&1)" == *"not a btrfs filesystem"* ]] && print_error "Root filesystem isn't btrfs"

printf "Detecting snapshots ...\n" >&2 ;

## Submenu name
distro=$(awk -F "=" '/^NAME=/ {gsub(/"/, "", $2); print $2}' /etc/os-release)
submenuname=${GRUB_BTRFS_SUBMENUNAME:-"${distro:-Linux} snapshots"}
## Limit snapshots to show in the Grub menu (default=50)
limit_snap_show="${GRUB_BTRFS_LIMIT:-50}"
## How to sort snapshots list
btrfs_subvolume_sort="--sort=${GRUB_BTRFS_SUBVOLUME_SORT:-"-rootid"}"
## Customize GRUB directory, where "grub.cfg" file is saved
grub_directory=${GRUB_BTRFS_GRUB_DIRNAME:-"/boot/grub"}
## Customize BOOT directory, where kernels/initrams/microcode is saved.
boot_directory=${GRUB_BTRFS_BOOT_DIRNAME:-"/boot"}
## Customize GRUB-BTRFS.cfg directory, where "grub-btrfs.cfg" file is saved
grub_btrfs_directory=${GRUB_BTRFS_GBTRFS_DIRNAME:-${grub_directory}}
## Customize directory where "grub-btrfs.cfg" file is searched for by grub
grub_btrfs_search_directory=${GRUB_BTRFS_GBTRFS_SEARCH_DIRNAME:-"\${prefix}"}
## Password protection management for submenu
# Protection support for submenu (--unrestricted)
case "${GRUB_BTRFS_DISABLE_PROTECTION_SUBMENU,,}" in
    true)   unrestricted_access_submenu="--unrestricted ";;
    *)      unrestricted_access_submenu=""
esac
# Authorized users (--users foo,bar)
if [ -n "${GRUB_BTRFS_PROTECTION_AUTHORIZED_USERS}" ] ; then
    protection_authorized_users="--users ${GRUB_BTRFS_PROTECTION_AUTHORIZED_USERS} "
fi

## Probe informations of Root and Boot devices
# Probe info "Root partition"
root_device=$(${grub_probe} --target=device /) # Root device
root_uuid=$(${grub_probe} --device ${root_device} --target="fs_uuid" 2>/dev/null) # UUID of the root device
root_uuid_subvolume=$(btrfs subvolume show / 2>/dev/null) || print_error "UUID of the root subvolume is not available"; # If UUID of root subvolume is not available, then exit
root_uuid_subvolume=$(awk -F":" 'match($1, /(^[ \t]+UUID)/) {sub(/^[ \t]+/, "", $2); print $2}' <<< "$root_uuid_subvolume") # UUID of the root subvolume
# Probe info "Boot partition"
boot_device=$(${grub_probe} --target=device ${boot_directory}) # Boot device
boot_uuid=$(${grub_probe} --device ${boot_device} --target="fs_uuid" 2>/dev/null) # UUID of the boot device
boot_uuid_subvolume=$(btrfs subvolume show "$boot_directory" 2>/dev/null) || boot_uuid_subvolume=" UUID: $root_uuid_subvolume"; # If boot folder isn't a subvolume, then UUID=root_uuid_subvolume
boot_uuid_subvolume=$(awk -F":" 'match($1, /(^[ \t]+UUID)/) {sub(/^[ \t]+/, "", $2); print $2}' <<< "$boot_uuid_subvolume") # UUID of the boot subvolume
boot_hs=$(${grub_probe} --device ${boot_device} --target="hints_string" 2>/dev/null) # hints string
boot_fs=$(${grub_probe} --device ${boot_device} --target="fs" 2>/dev/null) # Type filesystem of boot device

## Parameters passed to the kernel
kernel_parameters="$GRUB_CMDLINE_LINUX $GRUB_CMDLINE_LINUX_DEFAULT $GRUB_BTRFS_SNAPSHOT_KERNEL_PARAMETERS"
## Mount point location
grub_btrfs_mount_point=$(mktemp -dt grub-btrfs.XXXXXXXXXX)
## Class for theme
CLASS="--class snapshots --class gnu-linux --class gnu --class os"
## save IFS
oldIFS=$IFS
## Detect uuid requirement (lvm,btrfs...)
check_uuid_required() {
if [ "${root_uuid}" = "" ] || [ "${GRUB_DISABLE_LINUX_UUID}" = "true" ] \
    || ! test -e "/dev/disk/by-uuid/${root_uuid}" \
    || ( test -e "${root_device}" && uses_abstraction "${root_device}" lvm ); then
    LINUX_ROOT_DEVICE=${root_device}
else
    LINUX_ROOT_DEVICE=UUID=${root_uuid}
fi
}
## Detect rootflags
detect_rootflags()
{
    local fstabflags=$(grep -oE '^\s*[^#][[:graph:]]+\s+/\s+btrfs\s+[[:graph:]]+' "${grub_btrfs_mount_point}/${snap_dir_name_trim}/etc/fstab" \
                        | sed -E 's/^.*[[:space:]]([[:graph:]]+)$/\1/;s/,?subvol(id)?=[^,$]+//g;s/^,//')
    rootflags="rootflags=${fstabflags:+$fstabflags,}${GRUB_BTRFS_ROOTFLAGS:+$GRUB_BTRFS_ROOTFLAGS,}"
}

unmount_grub_btrfs_mount_point()
{
if [[ -d "$grub_btrfs_mount_point" ]]; then
    local wait=true
    local wait_max=0
    printf "Unmount %s .." "$grub_btrfs_mount_point" >&2;
    while $wait; do
        if grep -qs "$grub_btrfs_mount_point" /proc/mounts; then
            wait_max=$((1+wait_max))
            if umount "$grub_btrfs_mount_point" >/dev/null 2>&1; then
                wait=false # umount successful
                printf " Success\n" >&2;
            elif [[ $wait_max = 10 ]]; then
                printf "\nWarning: Unable to unmount %s in %s\n" "$root_device" "$grub_btrfs_mount_point" >&2;
                break;
            else
                printf "." >&2 ; # output to show that the script is alive
                sleep 2 # wait 2 seconds before retry
            fi
        else
            wait=false # not mounted
            printf " Success\n" >&2;
        fi
    done
    if [[ "$wait" != true ]]; then
        if ! rm -d "$grub_btrfs_mount_point" >/dev/null 2>&1; then
            printf "Unable to delete %s: Device or ressource is busy\n" "$grub_btrfs_mount_point" >&2;
        fi
    fi
fi
}

## Create entry
entry()
{
    echo "$@" >> "$grub_btrfs_directory/grub-btrfs.new"
}

## menu entries
make_menu_entries()
{
## \" required for snap,kernels,init,microcode with space in their name
    entry "submenu '${title_menu}' {
    submenu '${title_submenu}' { echo }"
    for k in "${name_kernel[@]}"; do
        [[ ! -f "${boot_dir}"/"${k}" ]] && continue;
        kversion=${k#*"-"}
        for i in "${name_initramfs[@]}"; do
            if [[ "${name_initramfs}" != "x" ]] ; then
                # prefix_i=${i%%"-"*}
                suffix_i=${i#*"-"}
                # alt_suffix_i=${i##*"-"}
                if   [ "${kversion}" = "${suffix_i}" ];                 then i="${i}";
                elif [ "${kversion}.img" = "${suffix_i}" ];             then i="${i}";
                elif [ "${kversion}-fallback.img" = "${suffix_i}" ];    then i="${i}";
                elif [ "${kversion}.gz" = "${suffix_i}" ];              then i="${i}";
                else continue;
                fi
                for u in "${name_microcode[@]}"; do
                    if [[ "${name_microcode}" != "x" ]] ; then
                    entry "
    menuentry '  "${k}" & "${i}" & "${u}"' ${CLASS} "\$menuentry_id_option" 'gnulinux-snapshots-$boot_uuid' {"
                    else
                    entry "
    menuentry '  "${k}" & "${i}"' ${CLASS} "\$menuentry_id_option" 'gnulinux-snapshots-$boot_uuid' {"
                    fi
                    entry "\
        if [ x\$feature_all_video_module = xy ]; then
        insmod all_video
        fi
        set gfxpayload=keep
        insmod ${boot_fs}
        if [ x\$feature_platform_search_hint = xy ]; then
            search --no-floppy --fs-uuid  --set=root ${boot_hs} ${boot_uuid}
        else
            search --no-floppy --fs-uuid  --set=root ${boot_uuid}
        fi
        echo 'Loading Snapshot: "${snap_date_trim}" "${snap_dir_name_trim}"'
        echo 'Loading Kernel: "${k}" ...'
        linux \"${boot_dir_root_grub}/"${k}"\" root="${LINUX_ROOT_DEVICE}" ${kernel_parameters} ${rootflags}subvol=\""${snap_dir_name_trim}"\""
                    if [[ "${name_microcode}" != "x" ]] ; then
                        entry "\
        echo 'Loading Microcode & Initramfs: "${u}" "${i}" ...'
        initrd \"${boot_dir_root_grub}/"${u}"\" \"${boot_dir_root_grub}/"${i}"\""
                    else
                        entry "\
        echo 'Loading Initramfs: "${i}" ...'
        initrd \"${boot_dir_root_grub}/"${i}"\""
                    fi
                    entry "    }"
                    count_warning_menuentries=$((1+count_warning_menuentries))
                done
            else
                for u in "${name_microcode[@]}"; do
                    if [[ "${name_microcode}" != "x" ]] ; then
                    entry "
    menuentry '  "${k}" & "${u}"' ${CLASS} "\$menuentry_id_option" 'gnulinux-snapshots-$boot_uuid' {"
                    else
                    entry "
    menuentry '  "${k}"' ${CLASS} "\$menuentry_id_option" 'gnulinux-snapshots-$boot_uuid' {"
                    fi
                    entry "\
        if [ x\$feature_all_video_module = xy ]; then
        insmod all_video
        fi
        set gfxpayload=keep
        insmod ${boot_fs}
        if [ x\$feature_platform_search_hint = xy ]; then
            search --no-floppy --fs-uuid  --set=root ${boot_hs} ${boot_uuid}
        else
            search --no-floppy --fs-uuid  --set=root ${boot_uuid}
        fi
        echo 'Loading Snapshot: "${snap_date_trim}" "${snap_dir_name_trim}"'
        echo 'Loading Kernel: "${k}" ...'
        linux \"${boot_dir_root_grub}/"${k}"\" root="${LINUX_ROOT_DEVICE}" ${kernel_parameters} ${rootflags}subvol=\""${snap_dir_name_trim}"\""
                    if [[ "${name_microcode}" != "x" ]] ; then
                        entry "\
        echo 'Loading Microcode: "${u}" ...'
        initrd \"${boot_dir_root_grub}/"${u}"\""
                    fi
                    entry "    }"
                    count_warning_menuentries=$((1+count_warning_menuentries))
                done
            fi
        done
    done
    entry  "}"
}

## Trim a string from leading and trailing whitespaces
trim() {
    local var="$*"
    var="${var#"${var%%[![:space:]]*}"}"
    var="${var%"${var##*[![:space:]]}"}"
    echo -n "$var"
}

## List of snapshots on filesystem
snapshot_list()
{
    local snapper_info="info.xml"
    local timeshift_info="info.json"
    local date_snapshots=()
    local path_snapshots=()
    local type_snapshots=()
    local description_snapshots=()
    IFS=$'\n'
    for snap in $(btrfs subvolume list -sa "${btrfs_subvolume_sort}" /); do # Parse btrfs snapshots
        IFS=$oldIFS
        snap=(${snap})
        local path_snapshot=${snap[@]:13:${#snap[@]}}
        if [ "$path_snapshot" = "DELETED" ]; then continue; fi # Discard deleted snapshots
        [[ ${path_snapshot%%"/"*} == "<FS_TREE>" ]] && path_snapshot=${path_snapshot#*"/"} # Remove the "<FS_TREE>" string at the beginning of the path

        # ignore specific path during run "grub-mkconfig"
        if [ -n "${GRUB_BTRFS_IGNORE_SPECIFIC_PATH}" ] ; then
            for isp in "${GRUB_BTRFS_IGNORE_SPECIFIC_PATH[@]}" ; do
                [[ "${path_snapshot}" == "${isp}" ]] && continue 2;
            done
        fi
        if [ -n "${GRUB_BTRFS_IGNORE_PREFIX_PATH}" ] ; then
            for isp in "${GRUB_BTRFS_IGNORE_PREFIX_PATH[@]}" ; do
                [[ "${path_snapshot}" == "${isp}"/* ]] && continue 2;
            done
        fi
        [[ ! -d "$grub_btrfs_mount_point/$path_snapshot/boot" ]] && continue; # Discard snapshots without /boot folder

        # Parse Snapper & timeshift informations
        local type_snapshot="N/A"
        local description_snapshot="N/A"
        if [[ -s "$grub_btrfs_mount_point/${path_snapshot%"/"*}/$snapper_info" ]] ; then
            type_snapshot=$(awk -F"<|>" 'match($2, /^type/) {print $3}' "$grub_btrfs_mount_point/${path_snapshot%"/"*}/$snapper_info") # search matching string beginning "type"
            description_snapshot=$(awk -F"<|>" 'match($2, /^description/) {print $3}' "$grub_btrfs_mount_point/${path_snapshot%"/"*}/$snapper_info") # search matching string beginning "description"
        elif [[ -s "$grub_btrfs_mount_point/${path_snapshot%"/"*}/$timeshift_info" ]] ; then
            type_snapshot=$(awk -F" : " 'match($1, /^[ \t]+"tags"/) {gsub(/"|,/,"");print $2}' "$grub_btrfs_mount_point/${path_snapshot%"/"*}/$timeshift_info") # search matching string beginning "tags"
            description_snapshot=$(awk -F" : " 'match($1, /^[ \t]+"comments"/) {gsub(/"|,/,"");print $2}' "$grub_btrfs_mount_point/${path_snapshot%"/"*}/$timeshift_info") # search matching string beginning "comments"
        fi
        [[ -z "$type_snapshot" ]] && type_snapshot=("N/A")
        [[ -z "$description_snapshot" ]] && description_snapshot=("N/A")

        # ignore specific {type,tag,description} of snapshot during run "grub-mkconfig"
        if [ -n "${GRUB_BTRFS_IGNORE_SNAPSHOT_TYPE}" ] ; then
            for ist in "${GRUB_BTRFS_IGNORE_SNAPSHOT_TYPE[@]}" ; do
                [[ "${type_snapshot}" == "${ist}" ]] && continue 2;
            done
        fi
        if [ -n "${GRUB_BTRFS_IGNORE_SNAPSHOT_DESCRIPTION}" ] ; then
            for isd in "${GRUB_BTRFS_IGNORE_SNAPSHOT_DESCRIPTION[@]}" ; do
                [[ "${description_snapshot}" == "${isd}" ]] && continue 2;
            done
        fi

        local date_snapshot="${snap[@]:10:2}"
        date_snapshots+=("$date_snapshot")
        path_snapshots+=("$path_snapshot")
        type_snapshots+=("$type_snapshot")
        description_snapshots+=("$description_snapshot")
    done

    # Find max length of a snapshot date, needed for pretty formatting
    local max_date_length=0
    for i in "${date_snapshots[@]}"; do
        local length="${#i}"
        [[ "$length" -gt "$max_date_length" ]] && max_date_length=$length
    done

    # Find max length of a snapshot name, needed for pretty formatting
    local max_path_length=0
    for i in "${path_snapshots[@]}"; do
        local length="${#i}"
        [[ "$length" -gt "$max_path_length" ]] && max_path_length=$length
    done

    # Find max length of a snapshot type, needed for pretty formatting
    local max_type_length=0
    for i in "${type_snapshots[@]}"; do
        local length="${#i}"
        [[ "$length" -gt "$max_type_length" ]] && max_type_length=$length
    done

    # Find max length of a snapshot description, needed for pretty formatting
    local max_description_length=0
    for i in "${description_snapshots[@]}"; do
        local length="${#i}"
        [[ "$length" -gt "$max_description_length" ]] && max_description_length=$length
    done

    for i in "${!path_snapshots[@]}"; do
        printf -v entry "%-${max_date_length}s | %-${max_path_length}s | %-${max_type_length}s | %-${max_description_length}s |" "${date_snapshots[$i]}" "${path_snapshots[$i]}" "${type_snapshots[$i]}" "${description_snapshots[$i]}"
        echo "$entry"
    done

    IFS=$oldIFS
}

## Parse snapshots in snapshot_list
parse_snapshot_list()
{
    snap_date=" $(echo "$item" | cut -d'|' -f1)" # column_1, first space is necessary for pretty formatting
    snap_date_trim="$(trim "$snap_date")"

    snap_dir_name="$(echo "$item" | cut -d'|' -f2)" # column_2
    snap_dir_name_trim="$(trim "$snap_dir_name")"
    snap_snapshot="$snap_dir_name" # Used by "title_format" function

    snap_type="$(echo "$item" | cut -d'|' -f3)" # column_3

    snap_description="$(echo "$item" | cut -d'|' -f4)" # column_4
}

## Detect kernels in "boot_directory"
detect_kernel()
{
    list_kernel=()
    # Original kernel (auto-detect)
    for okernel in  "${boot_dir}"/vmlinuz-* \
                    "${boot_dir}"/vmlinux-* \
                    "${boot_dir}"/kernel-* ; do
        [[ ! -f "${okernel}" ]] && continue;
        list_kernel+=("$okernel")
    done

    # Custom name kernel in "GRUB_BTRFS_NKERNEL"
    if [ -n "${GRUB_BTRFS_NKERNEL}" ] ; then
        for ckernel in "${boot_dir}/${GRUB_BTRFS_NKERNEL[@]}" ; do
            [[ ! -f "${ckernel}" ]] && continue;
            list_kernel+=("$ckernel")
        done
    fi
}

## Detect initramfs in "boot_directory"
detect_initramfs()
{
    list_initramfs=()
    # Original initramfs (auto-detect)
    for oinitramfs in   "${boot_dir}"/initrd.img-* \
                        "${boot_dir}"/initramfs-* \
                        "${boot_dir}"/initrd-* ; do
        [[ ! -f "${oinitramfs}" ]] && continue;
        list_initramfs+=("$oinitramfs")
    done

    # Custom name initramfs in "GRUB_BTRFS_NINIT"
    if [ -n "${GRUB_BTRFS_NINIT}" ] ; then
        for cinitramfs in "${boot_dir}/${GRUB_BTRFS_NINIT[@]}" ; do
            [[ ! -f "${cinitramfs}" ]] && continue;
            list_initramfs+=("$cinitramfs")
        done
    fi
    if [ -z "${list_initramfs}" ]; then list_initramfs=(x); fi
}

## Detect microcode in "boot_directory"
detect_microcode()
{
    list_ucode=()
    # Original intel/amd microcode (auto-detect)
    # See "https://www.gnu.org/software/grub/manual/grub/html_node/Simple-configuration.html"
    for oiucode in  "${boot_dir}"/intel-uc.img \
                    "${boot_dir}"/intel-ucode.img \
                    "${boot_dir}"/amd-uc.img \
                    "${boot_dir}"/amd-ucode.img \
                    "${boot_dir}"/early_ucode.cpio \
                    "${boot_dir}"/microcode.cpio; do
        [[ ! -f "${oiucode}" ]] && continue;
        list_ucode+=("$oiucode")
    done

    # Custom name microcode in "GRUB_BTRFS_CUSTOM_MICROCODE"
    if [ -n "${GRUB_BTRFS_CUSTOM_MICROCODE}" ] ; then
        for cucode in "${boot_dir}/${GRUB_BTRFS_CUSTOM_MICROCODE[@]}" ; do
            [[ ! -f "${cucode}" ]] && continue
            list_ucode+=("$cucode")
        done
    fi
    if [ -z "${list_ucode}" ]; then list_ucode=(x); fi
}

## Title format in Grub-menu
declare -A title_column=( [date]=Date [snapshot]=Snapshot [type]=Type [description]=Description ) # Column title that appears in the header
title_format()
{
    title_menu="|" # "|" is for visuals only
    title_submenu="|" # "|" is for visuals only
    [[ -z "${GRUB_BTRFS_TITLE_FORMAT}" ]] && GRUB_BTRFS_TITLE_FORMAT=("date" "snapshot" "type" "description"); # Default parameters
    for key in "${!GRUB_BTRFS_TITLE_FORMAT[@]}"; do
            [[ ${GRUB_BTRFS_TITLE_FORMAT[$key],,} != "${title_column[${GRUB_BTRFS_TITLE_FORMAT[$key]}],,}" ]] && continue; # User used wrong parameter
            declare -n var="snap_${GRUB_BTRFS_TITLE_FORMAT[$key],,}" # $var is a indirect variable
            if [[ "${#var}" -lt "${#title_column[${GRUB_BTRFS_TITLE_FORMAT[$key],,}]}" ]]; then # Add extra spaces if length of $var is smaller than the length of column, needed for pretty formatting
                printf -v var "%-$(((${#title_column[${GRUB_BTRFS_TITLE_FORMAT[$key],,}]}-${#var})+${#var}))s" "${var}";
            fi
		    var="$(sed  "s/'//g"  <(echo "${var}"))"
            title_menu+="${var}|"
            title_submenu+=" $(trim "${var}") |"
    done
}
# Adds a header to the grub-btrfs.cfg file
header_menu()
{
    local header_entry=""
    [[ -z "${GRUB_BTRFS_TITLE_FORMAT}" ]] && GRUB_BTRFS_TITLE_FORMAT=("date" "snapshot" "type" "description"); # Default parameters
        for key in "${!GRUB_BTRFS_TITLE_FORMAT[@]}"; do
            [[ ${GRUB_BTRFS_TITLE_FORMAT[$key],,} != "${title_column[${GRUB_BTRFS_TITLE_FORMAT[$key]}],,}" ]] && continue; # User used wrong parameter
            declare -n var="snap_${GRUB_BTRFS_TITLE_FORMAT[$key],,}" # $var is a indirect variable
            # Center alignment, needed for pretty formatting
            local lenght_title_column_left=$((${#var}-${#title_column[${GRUB_BTRFS_TITLE_FORMAT[$key],,}]}))
            ((lenght_title_column_left%2)) && lenght_title_column_left=$((lenght_title_column_left+1));  # If the difference is an odd number, add an extra space
            lenght_title_column_left=$((((lenght_title_column_left/2)+${#title_column[${GRUB_BTRFS_TITLE_FORMAT[$key],,}]})));
            local lenght_title_column_right=$(((${#var}-lenght_title_column_left)+1)) #+1 is necessary for extra "|" character
            header_entry+=$(printf "%${lenght_title_column_left}s%${lenght_title_column_right}s" "${title_column[${GRUB_BTRFS_TITLE_FORMAT[$key],,}]}" "|") # Final "|" is for visuals only
        done
    sed -i "1imenuentry '|${header_entry}' { echo }" "$grub_btrfs_directory/grub-btrfs.new" # First "|" is for visuals only
}

## List of kernels, initramfs and microcode in snapshots
boot_bounded()
{
    # Initialize menu entries
    IFS=$'\n'
    for item in $(snapshot_list); do
        [[ ${limit_snap_show} -le 0 ]] && break; # fix: limit_snap_show=0
        IFS=$oldIFS
        parse_snapshot_list
        boot_dir="$grub_btrfs_mount_point/$snap_dir_name_trim$boot_directory"
        detect_kernel
        if [ -z "${list_kernel}" ]; then continue; fi
        name_kernel=("${list_kernel[@]##*"/"}")
        detect_initramfs
        name_initramfs=("${list_initramfs[@]##*"/"}")
        detect_microcode
        name_microcode=("${list_ucode[@]##*"/"}")
        detect_rootflags
        title_format
        boot_dir_root_grub="$(make_system_path_relative_to_its_root "${boot_dir}")" # convert "boot_directory" to root of GRUB (e.g /boot become /)
        make_menu_entries
        # show snapshot found during run "grub-mkconfig"
        if [[ "${GRUB_BTRFS_SHOW_SNAPSHOTS_FOUND:-"true"}" = "true" ]]; then
            printf "Found snapshot: %s\n" "$item" >&2 ;
        fi
        # Limit snapshots found during run "grub-mkconfig"
        count_limit_snap=$((1+count_limit_snap))
        [[ $count_limit_snap -ge $limit_snap_show ]] && break;
    done
    IFS=$oldIFS
}

boot_separate()
{
    boot_dir="${boot_directory}"
    boot_dir_root_grub="$(make_system_path_relative_to_its_root "${boot_dir}")" # convert "boot_directory" to root of GRUB (e.g /boot become /)
    detect_kernel
    if [ -z "${list_kernel}" ]; then print_error "Kernels not found."; fi
    name_kernel=("${list_kernel[@]##*"/"}")
    detect_initramfs
    name_initramfs=("${list_initramfs[@]##*"/"}")
    detect_microcode
    name_microcode=("${list_ucode[@]##*"/"}")

    # Initialize menu entries
    IFS=$'\n'
    for item in $(snapshot_list); do
        [[ ${limit_snap_show} -le 0 ]] && break; # fix: limit_snap_show=0
        IFS=$oldIFS
        parse_snapshot_list
        detect_rootflags
        title_format
        make_menu_entries
        # show snapshot found during run "grub-mkconfig"
        if [[ "${GRUB_BTRFS_SHOW_SNAPSHOTS_FOUND:-"true"}" = "true" ]]; then
            printf "Found snapshot: %s\n" "$item" >&2 ;
        fi
        # Limit snapshots found during run "grub-mkconfig"
        count_limit_snap=$((1+count_limit_snap))
        [[ $count_limit_snap -ge $limit_snap_show ]] && break;
    done
    IFS=$oldIFS
}

rm -f "$grub_btrfs_directory/grub-btrfs.new"
true > "$grub_btrfs_directory/grub-btrfs.new" # Create a "grub-btrfs.new" file in "grub_btrfs_directory"
# Create a backup of the "$grub_btrfs_directory/grub-btrfs.cfg" file if exist
if [ -e "$grub_btrfs_directory/grub-btrfs.cfg" ]; then
	mv -f "$grub_btrfs_directory/grub-btrfs.cfg" "$grub_btrfs_directory/grub-btrfs.cfg.bkp"
fi
# Create mount point then mounting
[[ ! -d $grub_btrfs_mount_point ]] && mkdir -p "$grub_btrfs_mount_point"
mount -o ro,subvolid=5 /dev/disk/by-uuid/"$root_uuid" "$grub_btrfs_mount_point/" > /dev/null
trap "unmount_grub_btrfs_mount_point" EXIT # unmounting mount point on EXIT signal
count_warning_menuentries=0 # Count menuentries
count_limit_snap=0 # Count snapshots
check_uuid_required
# Detects if /boot is a separate partition
[[ "${GRUB_BTRFS_OVERRIDE_BOOT_PARTITION_DETECTION,,}" == "true" ]] && printf "Override boot partition detection : enable \n" >&2 && boot_separate;
if [[ "$root_uuid" != "$boot_uuid" ]] || [[ "$root_uuid_subvolume" != "$boot_uuid_subvolume" ]]; then boot_separate ; else boot_bounded ; fi
# Make a submenu in GRUB (grub.cfg)
cat << EOF
if [ ! -e "${grub_btrfs_search_directory}/grub-btrfs.cfg" ]; then
echo ""
else
submenu '${submenuname}' ${protection_authorized_users}${unrestricted_access_submenu}{
    configfile "${grub_btrfs_search_directory}/grub-btrfs.cfg"
}
fi
EOF
# Show warn, menuentries exceeds 250 entries
[[ $count_warning_menuentries -ge 250 ]] && printf "Generated %s total GRUB entries. You might experience issues loading snapshots menu in GRUB.\n" "${count_warning_menuentries}" >&2 ;
# Show total found snapshots
if [[ "${GRUB_BTRFS_SHOW_TOTAL_SNAPSHOTS_FOUND:-"true"}" = "true" && -n "${count_limit_snap}" && "${count_limit_snap}" != "0" ]]; then
    printf "Found %s snapshot(s)\n" "${count_limit_snap}" >&2 ;
fi
# if no snapshot found, delete the "$grub_btrfs_directory/grub-btrfs.new" file and the "$grub_btrfs_directory/grub-btrfs.cfg.bkp" file and exit
if [[ "${count_limit_snap}" = "0" || -z "${count_limit_snap}" ]]; then
    rm -f "$grub_btrfs_directory/grub-btrfs.new" "$grub_btrfs_directory/grub-btrfs.cfg.bkp"
    print_error "No snapshots found."
fi
# Move "grub-btrfs.new" to "grub-btrfs.cfg"
header_menu
if "${bindir}/${GRUB_BTRFS_SCRIPT_CHECK:-grub-script-check}" "$grub_btrfs_directory/grub-btrfs.new"; then
    cat "$grub_btrfs_directory/grub-btrfs.new" > "$grub_btrfs_directory/grub-btrfs.cfg"
    rm -f "$grub_btrfs_directory/grub-btrfs.new" "$grub_btrfs_directory/grub-btrfs.cfg.bkp"
else
if [ -e "$grub_btrfs_directory/grub-btrfs.cfg.bkp" ]; then
        mv -f "$grub_btrfs_directory/grub-btrfs.cfg.bkp" "$grub_btrfs_directory/grub-btrfs.cfg"
fi
	print_error "Syntax errors were detected in generated ${grub_btrfs_directory}/grub-btrfs.new file. The old grub-btrfs.cfg file (if present) have been restored."
fi

# warn when this script is run but there is no entry in grub.cfg
grep "snapshots-btrfs" "${grub_directory}/grub.cfg" >/dev/null 2>&1 || printf "\nWARNING: '%s' needs to run at least once to generate the snapshots (sub)menu entry in grub the main menu. \
After that this script can run alone to generate the snapshot entries.\n\n" "${GRUB_BTRFS_MKCONFIG:-grub-mkconfig}" >&2 ;