diff --git a/41_snapshots-btrfs b/41_snapshots-btrfs
index 9d16057..077be8a 100644
--- a/41_snapshots-btrfs
+++ b/41_snapshots-btrfs
@@ -7,19 +7,19 @@ set -e
 ### variables modifiable ###
 ## fr: nom du sous-menu 
 ## en: Name of the submenu
-submenuname="ArchLinux Snapshots"
+submenuname=${GRUB_BTRFS_SUBMENUNAME:-"ArchLinux Snapshots"}
 ## fr: préfixe de l'entrée 
 ## en: Prefix entry
-prefixentry="Snapshot"
+prefixentry=${GRUB_BTRFS_PREFIXENTRY:-"Snapshot"}
 ## fr: nom(s) du ou des kernel(s)
 ## en: Name(s) of the kernel(s)
-nkernel=("vmlinuz-linux")
+nkernel=("${GRUB_BTRFS_NKERNEL[@]:-vmlinuz-linux}")
 ## fr: nom(s) de(s) l'init
 ## en: Name(s) of the init(s)
-ninit=("initramfs-linux.img" "initramfs-linux-fallback.img")
+ninit=("${GRUB_BTRFS_NINIT[@]:-initramfs-linux.img initramfs-linux-fallback.img}")
 ## fr: nom du microcode intel
 ## en: Name intel-ucode
-intel_ucode=("intel-ucode.img")
+intel_ucode=("${GRUB_BTRFS_INTEL_UCODE[@]:-intel-ucode.img}")
 
 
 ###########################
diff --git a/README.md b/README.md
index 7e34417..699361a 100644
--- a/README.md
+++ b/README.md
@@ -15,17 +15,17 @@ Makes a list of all snapshots, kernels, initramfs present on the filesystem and
 
 #### How to use it :
 
-1. Edit 41_snapshots-btrfs file :
+1. Add lines to /etc/default/grub as needed, defaults listed as examples:
+2. 
+	* submenuname = name menu appear in grub ( e.g: GRUB_BTRFS_SUBMENUNAME="ArchLinux Snapshots" )
 
-	* submenuname = name menu appear in grub ( e.g: submenuname="ArchLinux Snapshots" )
+	* prefixentry = add a name ahead your snapshots entries ( e.g: GRUB_BTRFS_PREFIXENTRY="Snapshot" )
 
-	* prefixentry = add a name ahead your snapshots entries ( e.g: prefixentry="Snapshot" )
+	* nkernel= name kernel you use it ( e.g: GRUB_BTRFS_NKERNEL=("vmlinuz-linux") )
 
-	* nkernel= name kernel you use it ( e.g: nkernel=("vmlinuz-linux") )
+	* ninit= name initramfs (ramdisk) you use it ( e.g: GRUB_BTRFS_NINIT=("initramfs-linux.img" "initramfs-linux-fallback.img") )
 
-	* ninit= name initramfs (ramdisk) you use it ( e.g: ninit=("initramfs-linux.img" "initramfs-linux-fallback.img") )
-
-	* intel_ucode= name intel microcode you use it ( e.g: intel_ucode=("intel-ucode.img") )
+	* intel_ucode= name intel microcode you use it ( e.g: GRUB_BTRFS_INTEL_UCODE=("intel-ucode.img") )
 
 2. Generate grub.cfg (on Archlinux is grub-mkconfig -o /boot/grub/grub.cfg )
 
@@ -39,4 +39,3 @@ Version 0.xx detect kernels,initramfs,intel microcode only in boot partition, no
 If kernels,initramfs,intel microcode, are present in boot partition but not in snapshot, entry will be created but not fonctional, you don't boot it.
 
 Version 1.xx will do it, release soon.
-