Add systemd.path as option to monitor for new Snapshots (#53)

* Use systemd.path to regenerate grub-btrfs.cfg

* Added option GRUB_BTRFS_DIRNAME

* Updated README

41_snapshots-btrfs

@@ -5,7 +5,7 @@
 # Written by: Antynea
 # BTC donation address: 1Lbvz244WA8xbpHek9W2Y12cakM6rDe5Rt
 # Github: https://github.com/Antynea/grub-btrfs
-#                                                                                                                                                                       #
+#                                                                                                                                                                       
 # Purpose: Include btrfs snapshots at boot options (grub-menu).
 #
 # What this script does:
@@ -20,7 +20,7 @@
 # - Refer 41_snapshots-btrfs_config for the list of available options and their default values.
 # - Place your configurations to either /etc/grub.d/41_snapshots-btrfs_config or /etc/default/grub.
 #
-# - Generate grub.cfg (on Arch Linux use grub-mkconfig -o /boot/grub/grub.cfg)
+# - Generate grub.cfg (on Arch Linux use grub-mkconfig -o /boot/$grub_directory/grub.cfg)
 #
 # - grub-btrfs automatically generates snapshots entries.
 # - You will see it appear different entries (e.g : Snapshot: [2014-02-12 11:24:37] my snapshot name overkill)
@@ -86,6 +86,8 @@ ignore_specific_path=("${GRUB_BTRFS_IGNORE_SPECIFIC_PATH[@]}")
 ## snapper's config name
 snapper_config=${GRUB_BTRFS_SNAPPER_CONFIG:-"root"}
 
+grub_directory=${GRUB_BTRFS_DIRNAME:-"grub"}
+
 ########################
 ### variables script ###
 ########################
@@ -108,6 +110,16 @@ gbgmp=$(mktemp -d)
 CLASS="--class snapshots --class gnu-linux --class gnu --class os"
 ## save IFS
 oldIFS=$IFS
+## Detect uuid requirement (lvm,btrfs...)
+check_uuid_required() {
+if [ "x${GRUB_DEVICE_UUID}" = "x" ] || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
+    || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
+    || ( test -e "${GRUB_DEVICE}" && uses_abstraction "${GRUB_DEVICE}" lvm ); then
+  LINUX_ROOT_DEVICE=${GRUB_DEVICE}
+else
+  LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}
+fi
+}
 
 
 ######################
@@ -137,10 +149,10 @@ test_btrfs()
 
 ## Create entry
 entry()	{
-echo "$@" >> "/boot/grub/grub-btrfs.cfg"
+echo "$@" >> "/boot/$grub_directory/grub-btrfs.cfg"
 # local arg="$@"
-# echo "${arg}" >> "/boot/grub/grub-btrfs.cfg"
+# echo "${arg}" >> "/boot/$grub_directory/grub-btrfs.cfg"
-# cat << EOF >> "/boot/grub/grub-btrfs.cfg"
+# cat << EOF >> "/boot/$grub_directory/grub-btrfs.cfg"
 # ${arg}
 # EOF
 }
@@ -185,7 +197,7 @@ make_menu_entries()
 		fi
 		echo 'Loading Snapshot: "${snap_date_time}" "${snap_dir_name}"'
 		echo 'Loading Kernel: "${k}" ...'
-		linux \"${boot_dir_root_grub}/"${k}"\" root=UUID=${root_uuid} rw rootflags=subvol=\""${snap_dir_name}"\" ${kernel_parameters}"
+		linux \"${boot_dir_root_grub}/"${k}"\" root="${LINUX_ROOT_DEVICE}" rw rootflags=subvol=\""${snap_dir_name}"\" ${kernel_parameters}"
 				if [[ -f "${boot_dir}"/"${u}" && "${i}" != "${prefix_i}-${kversion}-${alt_suffix_i}" ]] ; then
 					entry "\
 		echo 'Loading Microcode & Initramfs: "${u}" "${i}" ...'
@@ -482,8 +494,8 @@ printf "###### - Grub-btrfs: Snapshot detection started - ######\n" >&2 ;
 # if btrfs prog isn't installed, exit
 test_btrfs
 # Delete existing config
-#rm -f --preserve-root "/boot/grub/grub-btrfs.cfg"
+#rm -f --preserve-root "/boot/$grub_directory/grub-btrfs.cfg"
-> "/boot/grub/grub-btrfs.cfg"
+> "/boot/$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 $gbgmp/
@@ -491,6 +503,8 @@ mount -o subvolid=5 /dev/disk/by-uuid/$root_uuid $gbgmp/
 count_warning_menuentries=0
 # Count snapshots
 count_limit_snap=0
+# detect uuid requirement
+check_uuid_required
 # Detects if /boot is a separate partition
 if [[ "$root_uuid" != "$boot_uuid" ]]; then
 	printf "# Info: Separate boot partition detected \n" >&2 ;
@@ -512,7 +526,7 @@ fi
 if [[ "${count_limit_snap}" = "0" || -z "${count_limit_snap}" ]]; then
 	print_error "No snapshots found."
 fi
-root_grub="$(make_system_path_relative_to_its_root /boot/grub)"
+root_grub="$(make_system_path_relative_to_its_root /boot/$grub_directory)"
 # Make a submenu in GRUB (grub.cfg)
 cat << EOF
 submenu '${submenuname}' {

41_snapshots-btrfs_config

@@ -14,3 +14,4 @@
 # GRUB_BTRFS_IGNORE_SPECIFIC_PATH=("var/lib/docker")                         # Ignore specific path during run "grub-mkconfig"
 # GRUB_BTRFS_SNAPPER_CONFIG="root"                                           # Snapper's config name to use
 # GRUB_BTRFS_DISABLE="false"                                                 # Disable Grub-btrfs
+# GRUB_BTRFS_DIRNAME=grub							     # Might be grub2 on some systems ex. /boot/grub2/...

README.md

@@ -86,6 +86,10 @@ Add this lines to /etc/default/grub:
 
 	(Disable grub-btrfs)
 
+* GRUB_BTRFS_DIRNAME="grub"
+
+	(Name of the grub folder on /boot/)
+
 
 Generate grub.cfg (on Arch linux use grub-mkconfig -o /boot/grub/grub.cfg )
 
@@ -100,6 +104,8 @@ If you would like grub to automatically update when Snapper timeline snapshots a
 - `/etc/systemd/system/snapper-timeline.service.d/`
 - `/etc/systemd/system/snapper-cleanup.service.d/`
 
+Or copy `grub-btrfs.path` and `grub-btrfs.service` to `/etc/systemd/system/`
+
 Once the configuration files are in place, `systemctl daemon-reload` should be run to reload the units and make the changes active.
 
 ##

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 +1,10 @@
+[Unit]
+Description=Regenerate grub-btrfs.cfg
+
+[Service]
+Type=oneshot
+#Inital setup
+EnvironmentFile=/etc/grub.d/41_snapshots-btrfs_config
+ExecStartPre=-/bin/bash -c '[ ! -f "/boot/${GRUB_BTRFS_DIRNAME:-grub}/grub-btrfs.cfg" ] && grub2-mkconfig -o /boot/${GRUB_BTRFS_DIRNAME:-grub}/grub.cfg'
+#Regenerate grub-btrfs.cfg instead of the whole grub menu
+ExecStart=/etc/grub.d/41_snapshots-btrfs