Update installation section

Adds make help

10-update_grub.conf

@@ -1,7 +0,0 @@
-[Service]
-# Set the possible paths for `grub-mkconfig`
-Environment="PATH=/sbin:/bin:/usr/sbin:/usr/bin"
-# Load environment variables from the configuration
-EnvironmentFile=/etc/grub.d/41_snapshots-btrfs_config
-# Regenerate just '/boot/grub/grub-btrfs.cfg' if it exists, else regenerate the whole grub menu
-ExecStartPost=/bin/bash -c 'if [ -s "/boot/${GRUB_BTRFS_DIRNAME:-grub}/grub-btrfs.cfg" ]; then /etc/grub.d/41_snapshots-btrfs; else ${GRUB_BTRFS_MKCONFIG:-/usr/bin/grub-mkconfig} -o /boot/${GRUB_BTRFS_DIRNAME:-grub}/grub.cfg; fi'

41_snapshots-btrfs_config

@@ -1,19 +0,0 @@
-#!/usr/bin/env bash
-
-# GRUB_BTRFS_SUBMENUNAME="Arch Linux snapshots"                              # Name appearing in the Grub menu
-# GRUB_BTRFS_PREFIXENTRY="Snapshot:"                                         # Add a name ahead your snapshots entries in the Grub menu
-# GRUB_BTRFS_DISPLAY_PATH_SNAPSHOT="true"                                    # Show full path snapshot or only name in the Grub menu
-# GRUB_BTRFS_TITLE_FORMAT="p/d/n"                                            # Custom title, shows/hides p"prefix" d"date" n"name" in the Grub menu, separator "/", custom order available
-# GRUB_BTRFS_LIMIT="50"                                                      # Limit the number of snapshots populated in the GRUB menu
-# GRUB_BTRFS_SUBVOLUME_SORT="descending"                                     # Sort the found subvolumes by newest first ("descending") or oldest first ("ascending") and show $GRUB_BTRFS_LIMIT first entries.
-# GRUB_BTRFS_SHOW_SNAPSHOTS_FOUND="true"                                     # Show snapshots found during run "grub-mkconfig"
-# GRUB_BTRFS_SHOW_TOTAL_SNAPSHOTS_FOUND="true"                               # Show Total of snapshots found during run "grub-mkconfig"
-# GRUB_BTRFS_NKERNEL=("vmlinuz-linux")                                       # Use only if you have custom kernel name
-# GRUB_BTRFS_NINIT=("initramfs-linux.img" "initramfs-linux-fallback.img")    # Use only if you have custom initramfs name
-# GRUB_BTRFS_INTEL_UCODE=("intel-ucode.img")                                 # Use only if you have custom intel-ucode
-# 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/...
-# GRUB_BTRFS_OVERRIDE_BOOT_PARTITION_DETECTION="false"                       # Change to "true" if you have a boot partition in a different subvolume
-# GRUB_BTRFS_MKCONFIG=grub-mkconfig                                          # Might be 'grub2-mkconfig' on some systems

Makefile

@@ -0,0 +1,86 @@
+PKGNAME ?= grub-btrfs
+PREFIX ?= /usr
+
+INITCPIO ?= false
+SYSTEMD ?= true
+OPENRC ?= false
+
+SHARE_DIR = $(DESTDIR)$(PREFIX)/share
+LIB_DIR = $(DESTDIR)$(PREFIX)/lib
+BIN_DIR = $(DESTDIR)$(PREFIX)/bin
+
+.PHONY: install uninstall help
+
+install:
+	@if test "$(shell id -u)" != 0; then \
+		echo "You are not root, run this target as root please."; \
+		exit 1; \
+	fi
+	@install -Dm755 -t "$(DESTDIR)/etc/grub.d/" 41_snapshots-btrfs
+	@install -Dm644 -t "$(DESTDIR)/etc/default/grub-btrfs/" config
+	@# Systemd init system
+	@if test "$(SYSTEMD)" = true; then \
+		install -Dm644 -t "$(LIB_DIR)/systemd/system/" grub-btrfs.path; \
+		install -Dm644 -t "$(LIB_DIR)/systemd/system/" grub-btrfs.service; \
+	 fi
+	@# OpenRC init system
+	@if test "$(OPENRC)" = true; then \
+		install -Dm744 -t "$(BIN_DIR)/" grub-btrfs-openrc; \
+		install -Dm744 -t "$(DESTDIR)/etc/init.d/" grub-btrfsd; \
+	 fi
+	@# Arch Linux like distros only :
+	@if test "$(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 "$(SHARE_DIR)/licenses/$(PKGNAME)/" LICENSE
+	@install -Dm644 -t "$(SHARE_DIR)/doc/$(PKGNAME)/" README.md
+	@install -Dm644 "initramfs/readme.md" "$(SHARE_DIR)/doc/$(PKGNAME)/initramfs-overlayfs.md"
+
+uninstall:
+	@if test "$(shell id -u)" != 0; then \
+		echo "You are not root, run this target as root please."; \
+		exit 1; \
+	fi
+	@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 "$(LIB_DIR)/systemd/system/grub-btrfs.path"
+	@rm -f "$(LIB_DIR)/systemd/system/grub-btrfs.service"
+	@rm -f "$(BIN_DIR)/grub-btrfs-openrc;"
+	@rm -f "$(DESTDIR)/etc/init.d/grub-btrfsd;"
+	@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 "  SYSTEMD   | bool | include unit files             | true"
+	@echo "  OPENRC    | bool | include OpenRc daemon          | false"
+	@echo

README.md

@@ -1,131 +1,155 @@
-[![GitHub release](https://img.shields.io/github/release/Antynea/grub-btrfs.svg)](https://github.com/Antynea/grub-btrfs)
-  
-## 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)
 
-This is a version 3.xx of grub-btrfs
-##### BTC donation address: 1Lbvz244WA8xbpHek9W2Y12cakM6rDe5Rt
-##
-### Description
+## grub-btrfs 
 
-grub-btrfs, Include btrfs snapshots at boot options. (grub menu)
-##
-### What does grub-btrfs v3.xx do :
+This is a version 4.xx of grub-btrfs
+##### BTC donation address: `1Lbvz244WA8xbpHek9W2Y12cakM6rDe5Rt`
+- - -
+### Description :
+Improves Grub by adding "btrfs snapshots" to the Grub menu.
 
-Simple rollback using snapshots you made previously.
+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
+
+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 the type/tags and descriptions/comments of snapper/timeshift snapshots.
+* Automatically generate `grub.cfg` if you use the provided systemd service.
 
-* Automatically Detect kernel, initramfs and intel microcode in "/boot" directory on snapshots.
+- - -
+### Installation :
+#### Arch Linux
+The package is available in the community repository [grub-btrfs](https://archlinux.org/packages/community/any/grub-btrfs/)
+```
+pacman -S grub-btrfs
+```
 
-* Automatically Create corresponding "menuentry" in grub.cfg , which ensures a very easy rollback.
+#### Gentoo
+grub-btrfs is only available in the Gentoo User Repository (GURU) and not in the official Gentoo repository.  
+If you have not activated the GURU yet, do so by running:
+```
+emerge -av app-eselect/eselect-repository 
+eselect repository enable guru 
+emerge --sync 
+```
 
-* Automatically detect snapper and use snapper's snapshot description if available.
+Now merge grub-btrfs via 
+`emerge app-backup/grub-btrfs`
+
+#### Manual
+* Run `make install` or look into Makefile for instructions on where to put each file.
+* Run `make help` to check what options are available. 
+* Dependencies:
+  * [btrfs-progs](https://archlinux.org/packages/core/x86_64/btrfs-progs/)
+  * [grub](https://archlinux.org/packages/core/x86_64/grub/)
+  * [bash >4](https://archlinux.org/packages/core/x86_64/bash/)
+  * [gawk ](https://archlinux.org/packages/core/x86_64/gawk/)
+
+#### NOTE: All distros
+Generate your Grub menu after installation for the changes to take effect.  
+For example:  
+On **Arch Linux** or **Gentoo** use `grub-mkconfig -o /boot/grub/grub.cfg`.  
+On **Fedora** use `grub2-mkconfig -o /boot/grub2/grub.cfg`  
+On **Debian-like** distribution `update-grub` is an alias to `grub-mkconfig ...`
+- - -
+### 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 :
+#### Systemd
+1. If you would like grub-btrfs menu to automatically update when a snapshot is created or deleted:
+* Use `systemctl enable grub-btrfs.path`.
+  * `grub-btrfs.path` automatically (re)generates `grub-btrfs.cfg` when a modification appears in `/.snapshots` mount point (by default).
+  * If the `/.snapshots` mount point is already mounted, then use `systemctl start grub-btrfs.path` to start monitoring.  
+    Otherwise, the unit will automatically start monitoring when the mount point will be available.
+* If your snapshots location aren't mounted in `/.snapshots`, you must modify `grub-btrfs.path` unit using  
+`systemctl edit --full grub-btrfs.path` and run `systemctl reenable grub-btrfs.path` for changes take effect.  
+To find out the name of the `.mount` unit  
+use `systemctl list-units -t mount`.  
+	* For example: Timeshift mounts its snapshot folder in `/run/timeshift/backup/timeshift-btrfs/snapshots`.
+
+		Use `systemctl edit --full grub-btrfs.path`.
+		Then replace the whole block by:
+		```
+		[Unit]
+		Description=Monitors for new snapshots
+		DefaultDependencies=no
+		Requires=run-timeshift-backup.mount
+		After=run-timeshift-backup.mount
+		BindsTo=run-timeshift-backup.mount
+
+		[Path]
+		PathModified=/run/timeshift/backup/timeshift-btrfs/snapshots
+
+		[Install]
+		WantedBy=run-timeshift-backup.mount
+		```
+		Then save and finally run `systemctl reenable grub-btrfs.path` for changes take effect.  
+		Optional:  
+		If the `/run/timeshift/backup/timeshift-btrfs/snapshots` mount point is already mounted,  
+		then use `systemctl start grub-btrfs.path` to start monitoring.  
+		Otherwise, the unit will automatically start monitoring when the mount point will be available.  
+	* You can view your change to `systemctl cat grub-btrfs.path`.
+	* To revert change use `systemctl revert grub-btrfs.path`.
+
+2. If you would like grub-btrfs menu to automatically update on system restart/ shutdown:  
+[Look at this comment](https://github.com/Antynea/grub-btrfs/issues/138#issuecomment-766918328)  
+Currently not implemented
 ##
-### How to customize it:
+#### OpenRC
+1. If you would like grub-btrfs menu to automatically update when a snapshot is created or deleted:
+* Use `rc-config add grub-btrfsd default`, to start the grub-btrfsd daemon the next time the system boots. 
+	* To start `grub-btrfsd` right now, run `rc-service grub-btrfsd start`
+	* `grub-btrfsd` automatically watches the snapshot directory of timeshift (/run/timeshift/backup/timeshift-btrfs/snapshots)
+	and updates the grub-menu when a change occurs.
+* Currently untested for snapper
 
-You have the possibility to modify many parameters.
-Add this lines to /etc/default/grub:
-
-* GRUB_BTRFS_SUBMENUNAME="Arch Linux Snapshots"
-
-	(Name menu appearing in grub.)
-
-* GRUB_BTRFS_PREFIXENTRY="Snapshot:"
-
-	(Add a name ahead your snapshots entries.)
+2. If you would like grub-btrfs menu to automatically update on system restart/ shutdown:
+Just add the following script as `/etc/local.d/grub-btrfs-update.stop`
+	```
+	#!/bin/bash
 	
-* GRUB_BTRFS_DISPLAY_PATH_SNAPSHOT="true"
+	description="Update the grub btrfs snapshots menu"
+	name="grub-btrfs-update"
 	
-	(Show full path snapshot or only name, weird reaction with snapper)
+	depend()
+	{
+	  use localmount
+	}
 	
-* GRUB_BTRFS_TITLE_FORMAT="p/d/n"
-
- 	(Custom title, shows/hides p"prefix" d"date" n"name" in grub-menu, separator "/", custom order available)
-
-* GRUB_BTRFS_NKERNEL=("kernel-custom")
-
-	(Use it only if you have a custom kernel name)
-
-* GRUB_BTRFS_NINIT=("initramfs-custom.img" "initrd.img-custom")
-
-	(Use it only if you have a custom initramfs name)
-
-* GRUB_BTRFS_INTEL_UCODE=("intel-ucode.img")
-
-	(Use it only if you have custom intel-ucode)
-
-* GRUB_BTRFS_LIMIT="50"
-
-	(Limit the number of snapshots populated in the GRUB menu.)
-
-* GRUB_BTRFS_SUBVOLUME_SORT="descending"
-
-	(Sort the found subvolumes by newest first ("descending") or oldest first ("ascending"). 
-	If "ascending" is chosen then the $GRUB_BTRFS_LIMIT oldest
-	subvolumes will populate the menu.)
-
-* GRUB_BTRFS_SHOW_SNAPSHOTS_FOUND="true"
+	bash -c 'if [ -s "${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' 
+	```
 	
-	(Show snapshots found during run "grub-mkconfig") 
-	
-* GRUB_BTRFS_SHOW_TOTAL_SNAPSHOTS_FOUND="true"
-	
-	(Show Total number of snapshots found during run "grub-mkconfig")
+	Make your script executeable with `chmod a+x /etc/local.d/grub-btrfs-update.stop`.
 
-* GRUB_BTRFS_IGNORE_SPECIFIC_PATH=("var/lib/docker")
+* The extension ".stop" at the end of the filename indicates to locald that this script should be run at shutdown. 
+ If you want to run the menu update on startup instead, rename the file to `grub-btrfs-update.start`
+* Works for snapper and timeshift
 
-	(Ignore specific path during run "grub-mkconfig")
-
-* GRUB_BTRFS_SNAPPER_CONFIG="root"													
-
-	(Snapper's config name to use)
-
-* GRUB_BTRFS_DISABLE="true"
-
-	(Disable grub-btrfs)
-
-* GRUB_BTRFS_DIRNAME="grub"
-
-	(Name of the grub folder on /boot/)
-
-* GRUB_BTRFS_OVERRIDE_BOOT_PARTITION_DETECTION="false"
-	(Change to "true" if you have a boot partition in a different subvolume)
-
-* GRUB_BTRFS_MKCONFIG=grub-mkconfig
-
-    (Name or path of the 'grub-mkconfig' executable; this is 'grub2-mkconfig' on some systems)
-
-Generate grub.cfg (on Arch linux use grub-mkconfig -o /boot/grub/grub.cfg )
-
-grub-btrfs automatically generates snapshots entries.
-
-You will see it appear differents entries (e.g : Snapshot: 2018-01-03 15:08:41  @test1 )
-##
-### Automatically update grub
-
-If you would like grub to automatically update when Snapper timeline snapshots and cleanups occur, simply install `10-update_grub.conf` in the following locations:
-
-- `/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.
-
-##
-### Discussion
-Pour les francophones : https://forums.archlinux.fr/viewtopic.php?f=18&t=17177
-##
+##### 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)
-* [crossroads1112](https://github.com/crossroads1112)
-* [penetal](https://github.com/penetal)
-* [wesbarnett](https://github.com/wesbarnett)
-* [Psykar](https://github.com/Psykar)
-* [anyc](https://github.com/anyc)
-* [daftaupe](https://github.com/daftaupe)
-* [N-Parsons](https://github.com/N-Parsons)
-##
+* [Maxim Baz](https://github.com/maximbaz)
+* [Schievel1](https://github.com/Antynea/grub-btrfs/discussions/173#discussioncomment-1438790)
+* [All contributors](https://github.com/Antynea/grub-btrfs/graphs/contributors)
+- - -

config

@@ -0,0 +1,132 @@
+#!/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"
+
+# Custom title.
+# Shows/Hides "date" "snapshot" "type" "description" in the Grub menu, custom order available.
+# Default: ("date" "snapshot" "type" "description")
+#GRUB_BTRFS_TITLE_FORMAT=("date" "snapshot" "type" "description")
+
+# 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")
+
+# Ignore specific type/tag of snapshot during run "grub-mkconfig".
+# For snapper:
+# Type = single, pre, post.
+# For Timeshift:
+# Tag = boot, ondemand, hourly, daily, weekly, monthly.
+# Default: ("")
+#GRUB_BTRFS_IGNORE_SNAPSHOT_TYPE=("")
+
+# Ignore specific description of snapshot during run "grub-mkconfig".
+# e.g: timeline
+# Default: ("")
+#GRUB_BTRFS_IGNORE_SNAPSHOT_DESCRIPTION=("")
+
+# By default "grub-btrfs" automatically detects your boot partition,
+# either located at the system root or on a separate partition or in a subvolume,
+# Change to "true" if your boot partition isn't detected as separate.
+# 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
+
+# Name of grub-script-check command, use by "grub-btrfs"
+# Might be 'grub2-script-check' on some systems (Fedora ...)
+# For example, on Fedora : "grub2-script-check"
+# Default: grub-script-check
+#GRUB_BTRFS_SCRIPT_CHECK=grub2-script-check
+
+# Path of grub-mkconfig_lib file, use by "grub-btrfs"
+# Might be '/usr/share/grub2/grub-mkconfig_lib' on some systems (Opensuse ...)
+# Default: /usr/share/grub/grub-mkconfig_lib
+#GRUB_BTRFS_MKCONFIG_LIB=/usr/share/grub2/grub-mkconfig_lib
+
+# 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-openrc

@@ -0,0 +1,6 @@
+#!/bin/sh
+echo $$ > /run/grub-btrfsd.pid
+
+while true; do sleep 1 && inotifywait -e create -e delete /run/timeshift/backup/timeshift-btrfs/snapshots && sleep 5 && 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  ; done
+
+

grub-btrfs.path

@@ -1,8 +1,12 @@
 [Unit]
 Description=Monitors for new snapshots
+DefaultDependencies=no
+Requires=\x2esnapshots.mount
+After=\x2esnapshots.mount
+BindsTo=\x2esnapshots.mount
 
 [Path]
 PathModified=/.snapshots
 
 [Install]
-WantedBy=multi-user.target
+WantedBy=\x2esnapshots.mount

grub-btrfs.service

@@ -6,6 +6,6 @@ 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/grub.d/41_snapshots-btrfs_config
+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 "/boot/${GRUB_BTRFS_DIRNAME:-grub}/grub-btrfs.cfg" ]; then /etc/grub.d/41_snapshots-btrfs; else ${GRUB_BTRFS_MKCONFIG:-/usr/bin/grub-mkconfig} -o /boot/${GRUB_BTRFS_DIRNAME:-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' 

grub-btrfsd

@@ -0,0 +1,14 @@
+#!/sbin/openrc-run
+# Copyright 1999-2021 Gentoo Foundation
+# Distributed under the terms of the GNU General Public License v2
+
+name="grub-btrfs daemon"
+command="/usr/bin/grub-btrfs-openrc"
+pidfile="/run/{RC_SVCNAME}.pid"
+command_background=true
+
+depend() {
+   use localmount
+}
+
+

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.
+#