Adds a new config variable "GRUB_BTRFS_ROOTFLAGS" (#133)

Script:

Improves the rootflags option in the kernel command line:
- Remove "rw" flag.
- Parse fstab mountoptions and add them to rootflags:
Adds functionality to read in  snapshot specific mount flags
from the respective fstab and uses them in combination with the new 
config option, while the latter is prioritized.
Both places can, but don't need to define mount flags. If either of them
doesn't, it will simply not be taken into account.

Config file:

Adds a new config variable "GRUB_BTRFS_ROOTFLAGS":
- The new variable is used to include user-defined rootflags in the 
kernel command line of generated snapshot bootmenu entries.
See config file for more infos.

41_snapshots-btrfs

@@ -115,6 +115,13 @@ 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()
@@ -183,7 +190,7 @@ make_menu_entries()
         fi
         echo 'Loading Snapshot: "${snap_date_time}" "${snap_dir_name}"'
         echo 'Loading Kernel: "${k}" ...'
-        linux \"${boot_dir_root_grub}/"${k}"\" root="${LINUX_ROOT_DEVICE}" rw ${kernel_parameters} rootflags=subvol=\""${snap_dir_name}"\""
+        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}" "${i}" ...'
@@ -417,6 +424,8 @@ boot_bounded()
         detect_kernel
         if [ -z "${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
@@ -472,6 +481,8 @@ boot_separate()
         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 ;

Makefile

@@ -4,7 +4,7 @@ PREFIX ?= /usr
 SHARE_DIR = $(DESTDIR)$(PREFIX)/share
 LIB_DIR = $(DESTDIR)$(PREFIX)/lib
 
-.PHONY: install
+.PHONY: install uninstall help
 
 install:
 	@install -Dm755 -t "$(DESTDIR)/etc/grub.d/" 41_snapshots-btrfs
@@ -12,20 +12,49 @@ install:
 	@install -Dm644 -t "$(LIB_DIR)/systemd/system/" grub-btrfs.service
 	@install -Dm644 -t "$(LIB_DIR)/systemd/system/" grub-btrfs.path
 	@install -Dm644 -t "$(SHARE_DIR)/licenses/$(PKGNAME)/" LICENSE
-	@install -Dm644 "initramfs/Arch Linux/overlay_snap_ro-install" "$(LIB_DIR)/initcpio/install/grub-btrfs-overlayfs"	# Arch Linux only
-	@install -Dm644 "initramfs/Arch Linux/overlay_snap_ro-hook" "$(LIB_DIR)/initcpio/hooks/grub-btrfs-overlayfs"		# Arch Linux only
+	@# Arch Linux like distros only :
+	@if command -V mkinitcpio >/dev/null 2>&1; then \
+		install -Dm644 "initramfs/Arch Linux/overlay_snap_ro-install" "$(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:
-	rm -f "$(DESTDIR)/etc/grub.d/41_snapshots-btrfs"
-	rm -f "$(DESTDIR)/etc/default/grub-btrfs/config"
-	rm -f "$(LIB_DIR)/systemd/system/grub-btrfs.service"
-	rm -f "$(LIB_DIR)/systemd/system/grub-btrfs.path"
-	rm -f "$(SHARE_DIR)/licenses/$(PKGNAME)/LICENSE"
-	rm -f "$(DESTDIR)/boot/grub/grub-btrfs.cfg"
-	rm -f "$(LIB_DIR)/initcpio/install/grub-btrfs-overlayfs" # Arch Linux only
-	rm -f "$(LIB_DIR)/initcpio/hooks/grub-btrfs-overlayfs" # Arch Linux only
-	rm -rf "$(SHARE_DIR)/doc/$(PKGNAME)/" README.md
-	rm -rf "$(SHARE_DIR)/doc/$(PKGNAME)/initramfs-overlayfs.md"
-	rmdir --ignore-fail-on-non-empty "$(DESTDIR)/etc/default/grub-btrfs"
+	@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 ! command -V mkinitcpio >/dev/null 2>&1; 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: $(MAKE) [ <parameter>=<value> ... ] [ <action> ]"
+	@echo
+	@echo "  actions: install"
+	@echo "           uninstall"
+	@echo "           help"
+	@echo
+	@echo "  parameters | description                    | defaults"
+	@echo "  -----------+--------------------------------+----------------------------"
+	@echo "  DESTDIR    | install destination            | <unset>"
+	@echo "  PREFIX     | system tree prefix             | '/usr'"
+	@echo "  SHARE_DIR  | shared data location           | '\$$(DESTDIR)\$$(PREFIX)/share'"
+	@echo "  LIB_DIR    | system libraries location      | '\$$(DESTDIR)\$$(PREFIX)/lib'"
+	@echo "  PKGNAME    | name of the ditributed package | 'grub-btrfs'"
+	@echo

README.md

@@ -68,6 +68,10 @@ If you would like Grub to automatically update when a snapshot is made or delete
 		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)

config

@@ -54,6 +54,14 @@
 # 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.
@@ -85,10 +93,13 @@ GRUB_BTRFS_IGNORE_PREFIX_PATH=("var/lib/docker" "@var/lib/docker" "@/var/lib/doc
 # Default: "/boot"
 #GRUB_BTRFS_BOOT_DIRNAME="/boot"
 
-# Name/path of grub-mkconfig, use by "grub-btrfs.service"
-# Might be 'grub2-mkconfig' on some systems
+# 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"
-# Default: /usr/bin/grub-mkconfig
+# You can use only name or full path.
+# Default: grub-mkconfig
 #GRUB_BTRFS_MKCONFIG=/usr/bin/grub2-mkconfig
 
 # Snapper

grub-btrfs.service

@@ -8,4 +8,4 @@ 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=/bin/bash -c 'if [ -s "${GRUB_BTRFS_GRUB_DIRNAME:-/boot/grub}/grub-btrfs.cfg" ]; then /etc/grub.d/41_snapshots-btrfs; else ${GRUB_BTRFS_MKCONFIG:-/usr/bin/grub-mkconfig} -o ${GRUB_BTRFS_GRUB_DIRNAME:-/boot/grub}/grub.cfg; fi' 
+ExecStart=bash -c 'if [ -s "${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'