[make help] mention INITCPIO switch (#137)

This commit is an expansion to :
87b816345b

Since a new `make` parameter has been introduced, it should be mentioned
in the output of the `help` target.

Also, the table is being expanded by a new column describing the type of
data that each parameter may be assigned, like paths or boolean values.

41_snapshots-btrfs

@@ -1,136 +1,553 @@
-#! /bin/sh
+#! /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 start your system on a "snapshot" from the Grub menu.
+#   Supports manual snapshots, snapper ...
+#   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 microcode in "/boot" directory on snapshots.
+# - Automatically Create corresponding "menuentry" in grub.cfg
+# - Automatically detect snapper and use snapper's snapshot description if available.
+# - Automatically generate grub.cfg if you use the provided systemd service.
+#
+# Installation:
+# - Run `make install` or look into Makefile for instructions on where to put each file.
+#
+# Customization:
+#  Refer to config for the list of available options and their default values.
+#  Place your configurations to /etc/default/grub-btrfs/config.
+#
+# Automatically update Grub
+#  If you would like Grub to automatically update when a snapshots is made or deleted:
+#  - Use systemctl start/enable grub-btrfs.path
+#  - grub-btrfs.path automatically (re)generates grub.cfg when a modification appears in /.snapshots folder (by default).
+#  - If your snapshots aren't mounted in /.snapshots, you must modify the watch folder using systemctl edit grub-btrfs.path
+#  - See https://github.com/Antynea/grub-btrfs#automatically-update-grub
+#
+# Special thanks for assistance and contributions:
+# - My friends
+# - All contributors on Github
+#
+
 set -e
 
-. /usr/share/grub/grub-mkconfig_lib
-. /etc/default/grub
+prefix="/usr"
+exec_prefix="/usr"
+datarootdir="/usr/share"
+sysconfdir="/etc"
+grub_btrfs_config="${sysconfdir}/default/grub-btrfs/config"
 
-### variables modifiable ###
-## fr: nom du sous-menu 
-## en: Name of the submenu
-submenuname="ArchLinux Snapshots"
-## fr: préfixe de l'entrée 
-## en: Prefix entry
-prefixentry="Snapshot"
-## fr: nom(s) du ou des kernel(s)
-## en: Name(s) of the kernel(s)
-nkernel=("vmlinuz-linux")
-## fr: nom(s) de(s) l'init
-## en: Name(s) of the init(s)
-ninit=("initramfs-linux.img")
-## fr: nom du microcode intel
-## en: Name intel-ucode
-intel_ucode=("intel-ucode.img")
+[[ -f "$grub_btrfs_config" ]] && . "$grub_btrfs_config"
+. "$datarootdir/grub/grub-mkconfig_lib"
+. "${sysconfdir}/default/grub"
 
+### Variables in /etc/default/grub-btrfs/config
+## Disable Grub-btrfs (default=active)
+[[ "${GRUB_BTRFS_DISABLE:-"false"}" == "true" ]] && exit 0
+## Submenu name
+distro=$(awk -F "=" '/^NAME=/ {gsub(/"/, "", $2); print $2}' /etc/os-release)
+submenuname=${GRUB_BTRFS_SUBMENUNAME:-"${distro:-Linux} snapshots"}
+## Prefix entry
+prefixentry=${GRUB_BTRFS_PREFIXENTRY:-"Snapshot:"}
+## Limit snapshots to show in the Grub menu
+limit_snap_show="${GRUB_BTRFS_LIMIT:-50}"
+## How to sort snapshots list
+btrfssubvolsort=(--sort="${GRUB_BTRFS_SUBVOLUME_SORT:-"-rootid"}")
+## Snapper's config name
+snapper_config=${GRUB_BTRFS_SNAPPER_CONFIG:-"root"}
+## Customize GRUB directory, where "grub.cfg" file is saved
+grub_directory=${GRUB_BTRFS_GRUB_DIRNAME:-"/boot/grub"}
+## Customize BOOT directory, where kernels/initrams/microcode is saved.
+boot_directory=${GRUB_BTRFS_BOOT_DIRNAME:-"/boot"}
+## Password protection management for submenu
+# Protection support for submenu (--unrestricted)
+case "${GRUB_BTRFS_DISABLE_PROTECTION_SUBMENU:-"false"}" in
+    true)   unrestricted_access_submenu="--unrestricted ";;
+    *)      unrestricted_access_submenu=""
+esac
+# Authorized users (--users foo,bar)
+if [ ! -z "${GRUB_BTRFS_PROTECTION_AUTHORIZED_USERS}" ] ; then
+    protection_authorized_users="--users ${GRUB_BTRFS_PROTECTION_AUTHORIZED_USERS} "
+fi
 
-###########################
-### fr: DÉBUT DU SCRIPT ###
-### en: NAME OF SCRIPT  ###
-### fr: NE PAS TOUCHER  ###
-### en: DO NOT TOUCH    ###
-###########################
-## fr: internationalisation
-## en: Internationalization
-export TEXTDOMAIN=grub-btrfs-git
-export TEXTDOMAINDIR="/usr/share/locale"
-## fr: paramêtre des chaînes --hint
-## en: Parameter of the chains --hint (Translation unclear)
-pboot=$(${grub_probe} --target="hints_string" "/boot" 2>/dev/null)
-## fr: uuid de la partition root
-## en: UUID of the root partition
-uuid=$(${grub_probe} "/" --target="fs_uuid" 2>/dev/null)
-## fr: uuid de la partition boot
-## en: UUID of the boot partition
-buuid=$(${grub_probe} --target="fs_uuid" "/boot" 2>/dev/null)
-## fr: paramêtre passé au kernel
-## en: Parameters passed to the kernel
-params="$GRUB_CMDLINE_LINUX $GRUB_CMDLINE_LINUX_DEFAULT"
+### variables script
+## Probe info "Boot partition"
+# Boot device
+boot_device=$(${grub_probe} --target=device ${boot_directory})
+# hints string
+boot_hs=$(${grub_probe} --device ${boot_device} --target="hints_string" 2>/dev/null)
+# UUID of the boot partition
+boot_uuid=$(${grub_probe} --device ${boot_device} --target="fs_uuid" 2>/dev/null)
+# Type filesystem of boot partition
+boot_fs=$(${grub_probe} --device ${boot_device} --target="fs" 2>/dev/null)
+## Probe info "Root partition"
+# Type filesystem of root partition
+root_fs=$(${grub_probe} --target="fs" / 2>/dev/null)
+# Root device
+root_device=$(${grub_probe} --target=device /)
+# UUID of the root partition
+root_uuid=$(${grub_probe} --device ${root_device} --target="fs_uuid" 2>/dev/null)
+## Parameters passed to the kernel
+kernel_parameters="$GRUB_CMDLINE_LINUX $GRUB_CMDLINE_LINUX_DEFAULT"
+## Mount point location
+gbgmp=$(mktemp -d)
+## Class for theme
+CLASS="--class snapshots --class gnu-linux --class gnu --class os"
+## save IFS
+oldIFS=$IFS
+## Detect uuid requirement (lvm,btrfs...)
+check_uuid_required() {
+if [ "x${root_uuid}" = "x" ] || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
+    || ! test -e "/dev/disk/by-uuid/${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=$(grep -oE '^\s*[^#][[:graph:]]+\s+/\s+btrfs\s+[[:graph:]]+' "${gbgmp}/${snap_dir_name}/etc/fstab" \
+                        | sed -E 's/^.*[[:space:]]([[:graph:]]+)$/\1/;s/,?subvol(id)?=[^,$]+//g;s/^,//')
+    rootflags="rootflags=${fstabflags:+$fstabflags,}${GRUB_BTRFS_ROOTFLAGS:+$GRUB_BTRFS_ROOTFLAGS,}"
+}
 
+### Error Handling
+print_error()
+{
+    local arg="$@"
+    local nothing_to_do="If you think an error has occurred , please file a bug report at \" https://github.com/Antynea/grub-btrfs \"\nNothing to do. Abort.\n"
+    printf "${arg}\n${nothing_to_do}" >&2 ;
+    exit 0
+}
 
-# fr: on affiche le menu
-# en: Display the menu
-echo "submenu '$submenuname' {"
+test_btrfs()
+{
+    [[ "$root_fs" != "btrfs" ]] && print_error "Root partition isn't a btrfs filesystem.\nThis script only supports snapshots of the btrfs filesystem."
+    set +e
+    type btrfs >/dev/null 2>&1
+    if [[ $? -ne 0 ]]; then
+        print_error "Unable to retrieve info from btrfs filesystem, make sure you have btrfs-progs on your system."
+    fi
+    set -e
+}
 
-# fr: on traite la variable kernel
-# en: Treat the kernel variables (Translation unclear)
-for kernel in ${nkernel[@]}; do
-	# fr: on test si le(s) nom(s) du(des) kernel existe(nt), autrement on affiche une erreur et on sort
-	# en: Check the specified kernel(s) exist, if it/they don't, display an error and exit
-	if [ ! -f /boot/$kernel ]; then gettext_printf $"Error: /boot/$kernel, kernel does not exist" >&2; exit 1; fi
-	# fr: on vérifie le nombre de kernel présent, si >1 on crée un menu
-	# en: If there are >1 kernels, create a menu
-	if [ ${#nkernel[*]} != 1 ]; then echo "	submenu '$kernel' {
-		submenu '---> Kernel: $kernel <---' { echo }"; fi
-	
-	# fr: On liste les snapshots présent sur le système de fichier
-	# en: List filesystem snapshots
-	for item in $($bindir/btrfs subvolume list -s / --sort=-ogen | $bindir/awk '{print $NF}'); do
-		# fr: On écarte les snapshots avec un statut de suppression
-		# en: Discard deleted snapshots
-		if [ $item = "DELETED" ]; then continue; fi
-		# fr: affiche la liste des snapshots trouvés
-		# en: Output name of snapshot
-		gettext_printf $"Found Snapshot: %s\n" "$item" >&2
-		# fr: on crée un menu pour chaque snapshot présent (nom + date de création)
-		# en: Create a menu for remaining snapshots (name + creation date)
-		date_time=$($bindir/btrfs subvolume list -s / | $bindir/grep $item | $bindir/cut -d" " -f 11-12)
-		echo "		submenu '$prefixentry $item [$date_time]' {"
-		# fr: si plusieurs kernel on été trouvé, on affiche un titre indicatif
-		# en: if more than one kernel is found, create a menu
-		if [ ${#nkernel[*]} != 1 ]; then echo "			submenu '---> Kernel: $kernel <---' { echo }"; fi
-		# fr: on traite la variable de l'initramfs
-		# en: Treat the initramfs variables (Translation unclear)
-		for init in ${ninit[@]}; do
-			# fr: on test si le(s) nom(s) du(des) initramfs existe(nt), autrement on affiche une erreur et on sort
-			# en: Check the specified initramfs(es) exist, if it/they don't, display an error and exit
-			if [ ! -f /boot/$init ]; then gettext_printf $"Error: /boot/$init, initramfs does not exist" >&2; exit 1; fi
-			# fr: on traite chaque entrée des snapshots avec leurs kernel et initramfs respectifs
-			# en: Specify a kernel and initramfs for every snapshot
-			echo "\
-			menuentry '$item $init' --class arch --class gnu-linux --class gnu --class os "\$menuentry_id_option" 'gnulinux-snapshots-$uuid'{
-				load_video
-				set gfxpayload=$GRUB_GFXPAYLOAD_LINUX
-				if [ x"\$feature_platform_search_hint" = xy ]; then
-					search --no-floppy --fs-uuid --set=root $pboot $buuid
-				else
-					search --no-floppy --fs-uuid --set=root $buuid
-				fi
-				echo	'Loading Linux snapshot ...'"
-				# fr: on vérifie l'emplacement de la partition /boot
-				# en: Check the location of the /boot partition
-				if [ $uuid = $buuid ]; then
-					echo "\
-				linux	/$item/boot/$kernel root=UUID=$uuid rw rootflags=subvol=$item $params
-				echo    'Loading initial ramdisk ...'"
-				# fr: on vérifie la présence du microcode intel
-				# en: Check intel microcode exist
-					if [ -f /boot/$intel_ucode ]; then
-						echo "\
-				initrd	/$item/boot/$intel_ucode /$item/boot/$init"
-					else
-						echo "\
-				initrd	/$item/boot/$init"
-					fi
-				else
-					echo "\
-				linux	/$kernel root=UUID=$uuid rw rootflags=subvol=$item $params
-				echo    'Loading initial ramdisk ...'"
-				# fr: on vérifie la présence du microcode intel
-				# en: Check intel microcode exist
-				if [ -f /boot/$intel_ucode ]; then
-						echo "\
-				initrd	/$intel_ucode /$init"
-					else
-						echo "\
-				initrd  /$init"
-					fi
-				fi
-				echo "\
-			}"
-		done
-		echo "		}"
-	done
-	# fr: on oubli pas de fermer le menu si plusieurs kernels ont été trouvé
-	# en: Don't forget to close menus if more than one kernel is found
-	if [ ${#nkernel[*]} != 1 ]; then echo "	}"; fi
-done
-echo "}"
+### Script
+## Create entry
+entry()
+{
+echo "$@" >> "$grub_directory/grub-btrfs.cfg"
+}
+
+## menu entries
+make_menu_entries()
+{
+## \" required for snap,kernels,init,microcode with space in their name
+    entry "submenu '$title_menu' {
+    submenu '---> $title_menu <---' { echo }"
+    for k in "${name_kernel[@]}"; do
+        [[ ! -f "${boot_dir}"/"${k}" ]] && continue;
+        kversion=${k#*"-"}
+        for i in "${name_initramfs[@]}"; do
+            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_time}" "${snap_dir_name}"'
+        echo 'Loading Kernel: "${k}" ...'
+        linux \"${boot_dir_root_grub}/"${k}"\" root="${LINUX_ROOT_DEVICE}" ${kernel_parameters} ${rootflags}subvol=\""${snap_dir_name}"\""
+                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
+        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()
+{
+    # Query info from snapper if it is installed
+    type snapper >/dev/null 2>&1
+    if [ $? -eq 0 ]; then
+        if [ -s "/etc/snapper/configs/$snapper_config" ]; then
+            printf "Info: snapper detected, using config '$snapper_config'\n" >&2
+            local snapper_ids=($(snapper --no-dbus -t 0 -c "$snapper_config" list --disable-used-space | tail -n +3 | cut -d'|' -f 1))
+            local snapper_types=($(snapper --no-dbus -t 0 -c "$snapper_config" list --disable-used-space | tail -n +3 | cut -d'|' -f 2))
+
+            IFS=$'\n'
+            local snapper_descriptions=($(snapper --no-dbus -t 0 -c "$snapper_config" list --disable-used-space | tail -n +3 | rev | cut -d'|' -f 2 | rev))
+        else
+            printf "Warning: snapper detected but config '$snapper_config' does not exist\n" >&2
+        fi
+    fi
+
+    IFS=$'\n'
+
+    # Parse btrfs snapshots
+    local entries=()
+    local ids=()
+    local max_entry_length=0
+    for snap in $(btrfs subvolume list -sa "${btrfssubvolsort}" /); do
+        IFS=$oldIFS
+        snap=($snap)
+        local snap_path_name=${snap[@]:13:${#snap[@]}}
+
+        # Discard deleted snapshots
+        if [ "$snap_path_name" = "DELETED" ]; then continue; fi
+        [[ ${snap_path_name%%"/"*} == "<FS_TREE>" ]] && snap_path_name=${snap_path_name#*"/"}
+
+        # ignore specific path during run "grub-mkconfig"
+        if [ ! -z "${GRUB_BTRFS_IGNORE_SPECIFIC_PATH}" ] ; then
+            for isp in ${GRUB_BTRFS_IGNORE_SPECIFIC_PATH[@]} ; do
+                [[ "${snap_path_name}" == "${isp}" ]] && continue 2;
+            done
+        fi
+        if [ ! -z "${GRUB_BTRFS_IGNORE_PREFIX_PATH}" ] ; then
+            for isp in ${GRUB_BTRFS_IGNORE_PREFIX_PATH[@]} ; do
+                [[ "${snap_path_name}" == "${isp}"/* ]] && continue 2;
+            done
+        fi
+
+        # detect if /boot directory exists
+        [[ ! -d "$gbgmp/$snap_path_name/boot" ]] && continue;
+
+        local id="${snap_path_name//[!0-9]}" # brutal way to get id: remove everything non-numeric
+        ids+=("$id")
+
+        local entry="${snap[@]:10:2} | ${snap_path_name}"
+        entries+=("$entry")
+
+        # Find max length of a snapshot entry, needed for pretty formatting
+        local length="${#entry}"
+        [[ "$length" -gt "$max_entry_length" ]] && max_entry_length=$length
+    done
+
+    # Find max length of a snapshot type, needed for pretty formatting
+    local max_type_length=0
+    for id in "${ids[@]}"; do
+        for j in "${!snapper_ids[@]}"; do
+            local snapper_id="${snapper_ids[$j]//[[:space:]]/}"
+            if [[ "$snapper_id" == "$id" ]]; then
+                local snapper_type=$(trim "${snapper_types[$j]}")
+                local length="${#snapper_type}"
+                [[ "$length" -gt "$max_type_length" ]] && max_type_length=$length
+            fi
+        done
+    done
+
+    for i in "${!entries[@]}"; do
+        local id="${ids[$i]}"
+        local entry="${entries[$i]}"
+        for j in "${!snapper_ids[@]}"; do
+            local snapper_id="${snapper_ids[$j]//[[:space:]]/}"
+            # remove other non numeric characters
+            snapper_id="${snapper_id//\*/}"
+            snapper_id="${snapper_id//\+/}"
+            snapper_id="${snapper_id//-/}"
+            if [[ "$snapper_id" == "$id" ]]; then
+                local snapper_type=$(trim "${snapper_types[$j]}")
+                local snapper_description=$(trim "${snapper_descriptions[$j]}")
+                printf -v entry "%-${max_entry_length}s | %-${max_type_length}s | %s" "$entry" "$snapper_type" "$snapper_description"
+                break
+            fi
+        done
+        echo "$entry"
+    done
+
+    IFS=$oldIFS
+}
+
+## Detect kernels in "/boot"
+detect_kernel()
+{
+    list_kernel=()
+    # Original kernel (auto-detect)
+    for okernel in  "${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 [ ! -z "${GRUB_BTRFS_NKERNEL}" ] ; then
+        for ckernel in "${boot_dir}/${GRUB_BTRFS_NKERNEL[@]}" ; do
+            [[ ! -f "${ckernel}" ]] && continue;
+            list_kernel+=("$ckernel")
+        done
+    fi
+}
+
+## Detect initramfs in "/boot"
+detect_initramfs()
+{
+    list_initramfs=()
+    # Original initramfs (auto-detect)
+    for oinitramfs in   "${boot_dir}"/initrd.img-* \
+                        "${boot_dir}"/initrd-*.img \
+                        "${boot_dir}"/initrd-*.gz \
+                        "${boot_dir}"/initramfs-*.img \
+                        "${boot_dir}"/initramfs-*.gz ; do
+        [[ ! -f "${oinitramfs}" ]] && continue;
+        list_initramfs+=("$oinitramfs")
+    done
+
+    # Custom name initramfs in GRUB_BTRFS_NINIT
+    if [ ! -z "${GRUB_BTRFS_NINIT}" ] ; then
+        for cinitramfs in "${boot_dir}/${GRUB_BTRFS_NINIT[@]}" ; do
+            [[ ! -f "${cinitramfs}" ]] && continue;
+            list_initramfs+=("$cinitramfs")
+        done
+    fi
+}
+
+## Detect microcode in "/boot"
+detect_microcode()
+{
+    list_ucode=()
+    # Original intel/amd microcode (auto-detect)
+    # See "https://www.gnu.org/software/grub/manual/grub/html_node/Simple-configuration.html"
+    for oiucode in  "${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+=("$oiucode")
+    done
+
+    # Custom name microcode in GRUB_BTRFS_CUSTOM_MICROCODE
+    if [ ! -z "${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 "${list_ucode}" ]; then list_ucode=(x); fi
+}
+
+## Show full path snapshot or only name
+path_snapshot()
+{
+    case "${GRUB_BTRFS_DISPLAY_PATH_SNAPSHOT:-"true"}" in
+        true) name_snapshot=("${snap_full_name}");;
+        *)    name_snapshot=("${snap_full_name#*"/"}")
+    esac
+}
+
+## Title format in grub-menu
+title_format()
+{
+    case "${GRUB_BTRFS_TITLE_FORMAT:-"p/d/n"}" in
+        p/n/d)  title_menu="${prefixentry} ${name_snapshot} ${snap_date_time}";;
+        p/d)    title_menu="${prefixentry} ${snap_date_time}";;
+        p/n)    title_menu="${prefixentry} ${name_snapshot}";;
+        d/n)    title_menu="${snap_date_time} ${name_snapshot}";;
+        n/d)    title_menu="${name_snapshot} ${snap_date_time}";;
+        p)      title_menu="${prefixentry}";;
+        d)      title_menu="${snap_date_time}";;
+        n)      title_menu="${name_snapshot}";;
+        *)      title_menu="${prefixentry} ${snap_date_time} ${name_snapshot}"
+    esac
+}
+
+## List of kernels, initramfs and microcode in snapshots
+boot_bounded()
+{
+    # Initialize menu entries
+    IFS=$'\n'
+    for item in $(snapshot_list); do
+        [[ ${limit_snap_show} -le 0 ]] && break; # fix: limit_snap_show=0
+        IFS=$oldIFS
+        snap_full_name="$(echo "$item" | cut -d'|' -f2-)" # do not trim it to keep nice formatting
+        snap_dir_name="$(echo "$item" | cut -d'|' -f2)"
+        snap_dir_name="$(trim "$snap_dir_name")"
+        snap_date_time="$(echo "$item" | cut -d' ' -f1-2)"
+        snap_date_time="$(trim "$snap_date_time")"
+        
+        boot_dir="$gbgmp/$snap_dir_name$boot_directory"
+        # Kernel (Original + custom kernel)
+        detect_kernel
+        if [ -z "${list_kernel}" ]; then continue; fi
+        name_kernel=("${list_kernel[@]##*"/"}")
+        # Detect rootflags
+        detect_rootflags
+        # Initramfs (Original + custom initramfs)
+        detect_initramfs
+        if [ -z "${list_initramfs}" ]; then continue; fi
+        name_initramfs=("${list_initramfs[@]##*"/"}")
+        # microcode (auto-detect + custom microcode)
+        detect_microcode
+        name_microcode=("${list_ucode[@]##*"/"}")
+        # show snapshot found during run "grub-mkconfig"
+        if [[ "${GRUB_BTRFS_SHOW_SNAPSHOTS_FOUND:-"true"}" = "true" ]]; then
+            printf "Found snapshot: %s\n" "$item" >&2 ;
+        fi
+        # Show full path snapshot or only name
+        path_snapshot
+        # Title format in grub-menu
+        title_format
+        # convert /boot directory to root of GRUB (e.g /boot become /)
+        boot_dir_root_grub="$(make_system_path_relative_to_its_root "${boot_dir}")"
+        # Make menuentries
+        make_menu_entries
+        ### Limit snapshots found during run "grub-mkconfig"
+        count_limit_snap=$((1+$count_limit_snap))
+        [[ $count_limit_snap -ge $limit_snap_show ]] && break;
+        # Limit generation of menuentries if exceeds 250
+        # [[ $count_warning_menuentries -ge 250 ]] && break;
+    done
+    IFS=$oldIFS
+}
+boot_separate()
+{
+    boot_dir="${boot_directory}"
+    # convert /boot directory to root of GRUB (e.g /boot become /)
+    boot_dir_root_grub="$(make_system_path_relative_to_its_root "${boot_dir}")"
+
+    # Kernel (Original + custom kernel)
+    detect_kernel
+    if [ -z "${list_kernel}" ]; then print_error "Kernels not found."; fi
+    name_kernel=("${list_kernel[@]##*"/"}")
+    # Initramfs (Original + custom initramfs)
+    detect_initramfs
+    if [ -z "${list_initramfs}" ]; then print_error "Initramfs not found."; fi
+    name_initramfs=("${list_initramfs[@]##*"/"}")
+    # microcode (auto-detect + custom microcode)
+    detect_microcode
+    name_microcode=("${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
+        snap_full_name="$(echo "$item" | cut -d'|' -f2-)" # do not trim it to keep nice formatting
+        snap_dir_name="$(echo "$item" | cut -d'|' -f2)"
+        snap_dir_name="$(trim "$snap_dir_name")"
+        snap_date_time="$(echo "$item" | cut -d' ' -f1-2)"
+        snap_date_time="$(trim "$snap_date_time")"
+        # Detect rootflags
+        detect_rootflags
+        # show snapshot found during run "grub-mkconfig"
+        if [[ "${GRUB_BTRFS_SHOW_SNAPSHOTS_FOUND:-"true"}" = "true" ]]; then
+            printf "Found snapshot: %s\n" "$item" >&2 ;
+        fi
+        # Show full path snapshot or only name
+        path_snapshot
+        # Title format in grub-menu
+        title_format
+        # Make menuentries
+        make_menu_entries
+        # Limit snapshots found during run "grub-mkconfig"
+        count_limit_snap=$((1+$count_limit_snap))
+        [[ $count_limit_snap -ge $limit_snap_show ]] && break;
+        # Limit generation of menuentries if exceeds 250
+        # [[ $count_warning_menuentries -ge 250 ]] && break;
+    done
+    IFS=$oldIFS
+}
+
+### Start
+printf "Detecting snapshots ...\n" >&2 ;
+# Only support btrfs snapshots
+test_btrfs
+# Delete existing config
+#rm -f --preserve-root "$grub_directory/grub-btrfs.cfg"
+> "$grub_directory/grub-btrfs.cfg"
+# Create mount point then mounting
+[[ ! -d $gbgmp ]] && mkdir -p $gbgmp
+mount -o subvolid=5 /dev/disk/by-uuid/$root_uuid $gbgmp/
+# Count menuentries
+count_warning_menuentries=0
+# Count snapshots
+count_limit_snap=0
+# detect uuid requirement
+check_uuid_required
+# Detects if /boot is a separate partition
+if [[ "${GRUB_BTRFS_OVERRIDE_BOOT_PARTITION_DETECTION:-"false"}" == "true" ]]; then
+    printf "Info: Override boot partition detection : enable \n" >&2 ;
+    boot_separate
+else
+    if [[ "$root_uuid" != "$boot_uuid" ]]; then
+        printf "Info: Separate boot partition detected \n" >&2 ;
+        boot_separate
+    else
+        printf "Info: Separate boot partition not detected \n" >&2 ;
+        boot_bounded
+    fi
+fi
+# unmounting mount point
+umount $gbgmp
+# Show warn, menuentries exceeds 250 entries
+[[ $count_warning_menuentries -ge 250 ]] && printf "Generated ${count_warning_menuentries} total GRUB entries. You might experience issues loading snapshots menu in GRUB.\n" >&2 ;
+# printf "menuentries = $count_warning_menuentries \n" >&2 ;
+# Show total found snapshots
+if [[ "${GRUB_BTRFS_SHOW_TOTAL_SNAPSHOTS_FOUND:-"true"}" = "true" && ! -z "${count_limit_snap}" && "${count_limit_snap}" != "0" ]]; then
+    printf "Found ${count_limit_snap} snapshot(s)\n" >&2 ;
+fi
+# if no snapshot found, exit
+if [[ "${count_limit_snap}" = "0" || -z "${count_limit_snap}" ]]; then
+    print_error "No snapshots found."
+fi
+# Make a submenu in GRUB (grub.cfg)
+cat << EOF
+submenu '${submenuname}' ${protection_authorized_users}${unrestricted_access_submenu}{
+    configfile "\${prefix}/grub-btrfs.cfg"
+}
+EOF
+### End

Makefile

@@ -0,0 +1,63 @@
+PKGNAME ?= grub-btrfs
+PREFIX ?= /usr
+
+INITCPIO ?= false
+
+SHARE_DIR = $(DESTDIR)$(PREFIX)/share
+LIB_DIR = $(DESTDIR)$(PREFIX)/lib
+
+.PHONY: install uninstall help
+
+install:
+	@install -Dm755 -t "$(DESTDIR)/etc/grub.d/" 41_snapshots-btrfs
+	@install -Dm644 -t "$(DESTDIR)/etc/default/grub-btrfs/" config
+	@install -Dm644 -t "$(LIB_DIR)/systemd/system/" grub-btrfs.service
+	@install -Dm644 -t "$(LIB_DIR)/systemd/system/" grub-btrfs.path
+	@install -Dm644 -t "$(SHARE_DIR)/licenses/$(PKGNAME)/" LICENSE
+	@# Arch Linux like distros only :
+	@if test "$(INITCPIO)" = true; then \
+		install -Dm644 "initramfs/Arch Linux/overlay_snap_ro-install" "$(LIB_DIR)/initcpio/install/grub-btrfs-overlayfs"; \
+		install -Dm644 "initramfs/Arch Linux/overlay_snap_ro-hook" "$(LIB_DIR)/initcpio/hooks/grub-btrfs-overlayfs"; \
+	 fi
+	@install -Dm644 -t "$(SHARE_DIR)/doc/$(PKGNAME)/" README.md
+	@install -Dm644 "initramfs/readme.md" "$(SHARE_DIR)/doc/$(PKGNAME)/initramfs-overlayfs.md"
+
+uninstall:
+	@grub_dirname="$$(grep -oP '^[[:space:]]*GRUB_BTRFS_GRUB_DIRNAME=\K.*' "$(DESTDIR)/etc/default/grub-btrfs/config" | sed "s|\s*#.*||;s|(\s*\(.\+\)\s*)|\1|;s|['\"]||g")"; \
+	 rm -f "$${grub_dirname:-/boot/grub}/grub-btrfs.cfg"
+	@rm -f "$(DESTDIR)/etc/default/grub-btrfs/config"
+	@rm -f "$(DESTDIR)/etc/grub.d/41_snapshots-btrfs"
+	@rm -f "$(LIB_DIR)/systemd/system/grub-btrfs.service"
+	@rm -f "$(LIB_DIR)/systemd/system/grub-btrfs.path"
+	@rm -f "$(LIB_DIR)/initcpio/install/grub-btrfs-overlayfs"
+	@rm -f "$(LIB_DIR)/initcpio/hooks/grub-btrfs-overlayfs"
+	@# Arch Linux UNlike distros only :
+	@if test "$(INITCPIO)" != true && test -d "$(LIB_DIR)/initcpio"; then \
+		rmdir --ignore-fail-on-non-empty "$(LIB_DIR)/initcpio/install" || :; \
+		rmdir --ignore-fail-on-non-empty "$(LIB_DIR)/initcpio/hooks" || :; \
+		rmdir --ignore-fail-on-non-empty "$(LIB_DIR)/initcpio" || :; \
+	 fi
+	@rm -f "$(SHARE_DIR)/doc/$(PKGNAME)/README.md"
+	@rm -f "$(SHARE_DIR)/doc/$(PKGNAME)/initramfs-overlayfs.md"
+	@rm -f "$(SHARE_DIR)/licenses/$(PKGNAME)/LICENSE"
+	@rmdir --ignore-fail-on-non-empty "$(SHARE_DIR)/doc/$(PKGNAME)/" || :
+	@rmdir --ignore-fail-on-non-empty "$(SHARE_DIR)/licenses/$(PKGNAME)/" || :
+	@rmdir --ignore-fail-on-non-empty "$(DESTDIR)/etc/default/grub-btrfs" || :
+
+help:
+	@echo
+	@echo "Usage: $(MAKE) [ <parameter>=<value> ... ] [ <action> ]"
+	@echo
+	@echo "  actions: install"
+	@echo "           uninstall"
+	@echo "           help"
+	@echo
+	@echo "  parameter | type | description                    | defaults"
+	@echo "  ----------+------+--------------------------------+----------------------------"
+	@echo "  DESTDIR   | path | install destination            | <unset>"
+	@echo "  PREFIX    | path | system tree prefix             | '/usr'"
+	@echo "  SHARE_DIR | path | shared data location           | '\$$(DESTDIR)\$$(PREFIX)/share'"
+	@echo "  LIB_DIR   | path | system libraries location      | '\$$(DESTDIR)\$$(PREFIX)/lib'"
+	@echo "  PKGNAME   | name | name of the ditributed package | 'grub-btrfs'"
+	@echo "  INITCPIO  | bool | include mkinitcpio hook        | false"
+	@echo

README.md

@@ -1,4 +1,79 @@
-grub-btrfs
-==========
+[![GitHub release](https://img.shields.io/github/release/Antynea/grub-btrfs.svg)](https://github.com/Antynea/grub-btrfs/releases)
+![](https://img.shields.io/github/license/Antynea/grub-btrfs.svg)
 
-grub-btrfs, add support for btrfs snapshots into grub menu
+## grub-btrfs
+
+This is a version 4.xx of grub-btrfs
+##### BTC donation address: `1Lbvz244WA8xbpHek9W2Y12cakM6rDe5Rt`
+##
+### Description
+Improves Grub by adding "btrfs snapshots" to the Grub menu.
+
+You can start your system on a "snapshot" from the Grub menu.  
+Supports manual snapshots, snapper, timeshift ...
+
+##### Warning: booting on read-only snapshots can be tricky
+
+If you choose to do it, `/var/log` or even `/var` must be on a separate subvolume.  
+Otherwise, make sure your snapshots are writeable.  
+See [this ticket](https://github.com/Antynea/grub-btrfs/issues/92) for more info.
+
+This project includes its own solution.  
+Refer to the [documentation](https://github.com/Antynea/grub-btrfs/blob/master/initramfs/readme.md).
+
+##
+### What does grub-btrfs v4.xx do :
+* 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 snapper and use snapper's snapshot description if available.
+* Automatically generate `grub.cfg` if you use the provided systemd service.
+
+##
+### Installation :
+#### Arch Linux
+
+```
+pacman -S grub-btrfs
+```
+
+#### Manual
+
+* Run `make install` or look into Makefile for instructions on where to put each file.
+
+NOTE: Generate your Grub menu after installation for the changes to take effect.  
+On Arch Linux use `grub-mkconfig -o /boot/grub/grub.cfg`.
+
+##
+### Customization:
+
+You have the possibility to modify many parameters in `/etc/default/grub-btrfs/config`.  
+See [config file](https://github.com/Antynea/grub-btrfs/blob/master/config) for more information.
+
+##
+### Automatically update grub
+If you would like Grub to automatically update when a snapshot is made or deleted:
+* Use `systemctl start/enable grub-btrfs.path`.
+* `grub-btrfs.path` automatically (re)generates `grub.cfg` when a modification appears in `/.snapshots` folder (by default).
+* If your snapshots aren't mounted in `/.snapshots`, you must modify the watch folder using `systemctl edit grub-btrfs.path`.  
+	* For example: Timeshift mount its snapshots in `/run/timeshift/backup/timeshift-btrfs/snapshots` folder.
+
+		Use `systemctl edit grub-btrfs.path`.
+		Then wrote:
+		```
+		[Path]
+		PathModified=/run/timeshift/backup/timeshift-btrfs/snapshots
+		```
+		and finally save.
+	* You can view your change to `systemctl cat grub-btrfs.path`.
+	* To revert change use `systemctl revert grub-btrfs.path`.
+##### Warning:
+by default, `grub-mkconfig` command is used.  
+Might be `grub2-mkconfig` on some systems (Fedora ...).   
+Edit `GRUB_BTRFS_MKCONFIG` variable in `/etc/default/grub-btrfs/config` file to reflect this.
+##
+### Special thanks for assistance and contributions
+* [maximbaz](https://github.com/maximbaz)
+* [All contributors](https://github.com/Antynea/grub-btrfs/graphs/contributors)
+##

config

@@ -0,0 +1,122 @@
+#!/usr/bin/env bash
+
+# Disable grub-btrfs.
+# Default: "false"
+#GRUB_BTRFS_DISABLE="true"
+
+# Name appearing in the Grub menu.
+# Default: "Use distribution information from /etc/os-release."
+#GRUB_BTRFS_SUBMENUNAME="Arch Linux snapshots"
+
+# Add a name ahead your snapshots entries in the Grub menu.
+# Default: "Snapshot:"
+#GRUB_BTRFS_PREFIXENTRY="Snapshot:"
+
+# Show full path snapshot or only name in the Grub menu, weird reaction with snapper.
+# Default: "true"
+#GRUB_BTRFS_DISPLAY_PATH_SNAPSHOT="false"
+
+# Custom title.
+# shows/hides p"prefix" d"date" n"name" in the Grub menu, separator "/", custom order available.
+# Default: "p/d/n"
+#GRUB_BTRFS_TITLE_FORMAT="p/d/n"
+
+# Limit the number of snapshots populated in the GRUB menu.
+# Default: "50"
+#GRUB_BTRFS_LIMIT="50"
+
+# Sort the found subvolumes by "ogeneration" or "generation" or "path" or "rootid".
+# # See Sorting section to https://btrfs.wiki.kernel.org/index.php/Manpage/btrfs-subvolume#SUBCOMMAND
+# "-rootid" means list snapshot by new ones first.
+# Default: "-rootid"
+#GRUB_BTRFS_SUBVOLUME_SORT="+ogen,-gen,path,rootid"
+
+# Show snapshots found during run "grub-mkconfig"
+# Default: "true"
+#GRUB_BTRFS_SHOW_SNAPSHOTS_FOUND="false"
+
+# Show Total of snapshots found during run "grub-mkconfig"
+# Default: "true"
+#GRUB_BTRFS_SHOW_TOTAL_SNAPSHOTS_FOUND="true"
+
+# By default, "grub-btrfs" automatically detects most existing kernels.
+# If you have one or more custom kernels, you can add them here.
+# Default: ("")
+#GRUB_BTRFS_NKERNEL=("kernel-custom" "vmlinux-custom")
+
+# By default, "grub-btrfs" automatically detects most existing initramfs.
+# If you have one or more custom initramfs, you can add them here.
+# Default: ("")
+#GRUB_BTRFS_NINIT=("initramfs-custom.img" "initrd-custom.img" "otherinit-custom.gz")
+
+# By default, "grub-btrfs" automatically detects most existing microcodes.
+# If you have one or more custom microcodes, you can add them here.
+# Default: ("")
+#GRUB_BTRFS_CUSTOM_MICROCODE=("custom-ucode.img" "custom-uc.img "custom_ucode.cpio")
+
+# Comma seperated mount options to be used when booting a snapshot.
+# They can be defined here as well as in the "/" line inside the respective snapshots'
+# "/etc/fstab" files.  Mount options found in both places are combined, and this variable
+# takes priority over `fstab` entries.
+# NB: Do NOT include "subvol=..." or "subvolid=..." here.
+# Default: ""
+#GRUB_BTRFS_ROOTFLAGS="space_cache,commit=10,norecovery"
+
+# Ignore specific path during run "grub-mkconfig".
+# Only exact paths are ignored.
+# e.g : if `specific path` = @, only `@` snapshot will be ignored.
+# Default: ("@")
+GRUB_BTRFS_IGNORE_SPECIFIC_PATH=("@")
+
+# Ignore prefix path during run "grub-mkconfig".
+# Any path starting with the specified string will be ignored.
+# e.g : if `prefix path` = @, all snapshots beginning with "@/..." will be ignored.
+# Default: ("var/lib/docker" "@var/lib/docker" "@/var/lib/docker")
+GRUB_BTRFS_IGNORE_PREFIX_PATH=("var/lib/docker" "@var/lib/docker" "@/var/lib/docker")
+
+# By default "grub-btrfs" automatically detects your boot partition,
+# either located at the system root or on a separate partition,
+# but cannot detect if it is in a subvolume.
+# Change to "true" if you have a boot partition in a different subvolume.
+# Default: "false"
+#GRUB_BTRFS_OVERRIDE_BOOT_PARTITION_DETECTION="true"
+
+# Location of the folder containing the "grub.cfg" file.
+# Use by grub-btrfs to save the file "grub-btrfs.cfg".
+# Might be grub2 on some systems.
+# For example, on Fedora with EFI : "/boot/efi/EFI/fedora"
+# Default: "/boot/grub"
+#GRUB_BTRFS_GRUB_DIRNAME="/boot/grub2"
+
+# Location of kernels/initramfs/microcode.
+# Use by "grub-btrfs" to detect the boot partition and the location of kernels/initrafms/microcodes.
+# Default: "/boot"
+#GRUB_BTRFS_BOOT_DIRNAME="/boot"
+
+# Name/path of grub-mkconfig command, use by "grub-btrfs.service"
+# Might be 'grub2-mkconfig' on some systems (Fedora ...)
+# Default paths are /sbin:/bin:/usr/sbin:/usr/bin,
+# if your path is missing, report it on the upstream project.
+# For example, on Fedora : "/sbin/grub2-mkconfig"
+# You can use only name or full path.
+# Default: grub-mkconfig
+#GRUB_BTRFS_MKCONFIG=/usr/bin/grub2-mkconfig
+
+# Snapper
+# Snapper's config name to use
+# Default: "root"
+#GRUB_BTRFS_SNAPPER_CONFIG="root"
+
+# Password protection management for submenu,snapshots
+# Refer to the Grub documentation https://www.gnu.org/software/grub/manual/grub/grub.html#Authentication-and-authorisation
+# and this comment https://github.com/Antynea/grub-btrfs/issues/95#issuecomment-682295660
+#
+# Add authorized usernames separate by comma (foo,bar)
+# When Grub's password protection is enabled, the superuser is authorized by default, it isn't necessary to add it
+# Default: ""
+#GRUB_BTRFS_PROTECTION_AUTHORIZED_USERS="foo,bar"
+#
+# Disable authentication support for submenu of Grub-btrfs only (--unrestricted)
+# doesn't work if GRUB_BTRFS_PROTECTION_AUTHORIZED_USERS isn't empty
+# Default: "false"
+#GRUB_BTRFS_DISABLE_PROTECTION_SUBMENU="true"

grub-btrfs.path

@@ -0,0 +1,8 @@
+[Unit]
+Description=Monitors for new snapshots
+
+[Path]
+PathModified=/.snapshots
+
+[Install]
+WantedBy=multi-user.target

grub-btrfs.service

@@ -0,0 +1,11 @@
+[Unit]
+Description=Regenerate grub-btrfs.cfg
+
+[Service]
+Type=oneshot
+# Set the possible paths for `grub-mkconfig`
+Environment="PATH=/sbin:/bin:/usr/sbin:/usr/bin"
+# Load environment variables from the configuration
+EnvironmentFile=/etc/default/grub-btrfs/config
+# Regenerate just '/boot/grub/grub-btrfs.cfg' if it exists and is not empty, else regenerate the whole grub menu
+ExecStart=bash -c 'if [ -s "${GRUB_BTRFS_GRUB_DIRNAME:-/boot/grub}/grub-btrfs.cfg" ]; then /etc/grub.d/41_snapshots-btrfs; else ${GRUB_BTRFS_MKCONFIG:-grub-mkconfig} -o ${GRUB_BTRFS_GRUB_DIRNAME:-/boot/grub}/grub.cfg; fi' 

initramfs/Arch Linux/overlay_snap_ro-hook

@@ -0,0 +1,15 @@
+#!/usr/bin/ash
+
+run_latehook() {
+	local root_mnt="/new_root"
+	local current_dev=$(resolve_device "$root"); # resolve devices for blkid
+	if [[ $(blkid "${current_dev}" -s TYPE -o value) = "btrfs" ]] && [[ $(btrfs property get ${root_mnt} ro) != "ro=false" ]]; then # run only on a read only snapshot
+		local lower_dir=$(mktemp -d -p /)
+		local ram_dir=$(mktemp -d -p /)
+		mount --move ${root_mnt} ${lower_dir} # move new_root to lower_dir
+		mount -t tmpfs cowspace ${ram_dir}  #meuh!!! space, you can't test !
+		mkdir -p ${ram_dir}/upper
+		mkdir -p ${ram_dir}/work
+		mount -t overlay -o lowerdir=${lower_dir},upperdir=${ram_dir}/upper,workdir=${ram_dir}/work rootfs ${root_mnt}
+	fi
+}

initramfs/Arch Linux/overlay_snap_ro-install

@@ -0,0 +1,18 @@
+#!/bin/bash
+
+build() {
+    add_module btrfs
+    add_module overlay
+    add_binary btrfs
+    add_binary btrfsck
+    add_binary blkid
+    add_runscript
+}
+
+help() {
+    cat <<HELPEOF
+This hook uses overlayfs to boot on a read only snapshot.
+HELPEOF
+}
+
+# vim: set ft=sh ts=4 sw=4 et:

initramfs/readme.md

@@ -0,0 +1,45 @@
+### Description :
+
+Booting on a snapshot in read-only mode can be tricky.  
+An elegant way is to boot this snapshot using overlayfs (included in the kernel ≥ 3.18).
+
+Using overlayfs, the booted snapshot will behave like a live-cd in non-persistent mode.  
+The snapshot will not be modified, the system will be able to boot correctly, because a writeable folder will be included in the ram.  
+(no more problems due to `/var` not open for writing)
+
+Any changes in this system thus started will be lost when the system is rebooted/shutdown.
+
+To do this, it is necessary to modify the initramfs.  
+This means that any snapshot that does not include this modified initramfs will not be able to benefit from it.  
+(except for separate boot partitions)
+#
+### Installation :
+#### Arch Linux
+1.
+`Pacman -S grub-btrfs`  
+Or if you use git  
+copy the `overlay_snap_ro-install` file to `/etc/initcpio/install/grub-btrfs-overlayfs`  
+copy the `overlay_snap_ro-hook` file to `/etc/initcpio/hooks/grub-btrfs-overlayfs`  
+You must rename the files. (I did it above)
+
+For example :  
+`overlay_snap_ro-install` to `grub-btrfs-overlayfs`  
+`overlay_snap_ro-hook` to `grub-btrfs-overlayfs`  
+Keep in mind that the files must have exactly the same name to ensure a match.
+
+2.
+Edit the file `/etc/mkinitcpio.conf`  
+Added hook `grub-btrfs-overlayfs` at the end of the line `HOOKS`.
+
+For example :  
+`HOOKS=(base udev autodetect modconf block filesystems keyboard fsck grub-btrfs-overlayfs)`  
+You notice that the name of the `hook` must match the name of the 2 installed files. (don't forget it)
+
+3.
+Re-generate your initramfs  
+`mkinitcpio -P` (option -P means, all preset present in `/etc/mkinitcpio.d`)
+
+#### Other distribution
+Refer to your distribution's documentation  
+or contribute to this project to add a paragraph.
+#