2 files changed, 22 insertions, 4 deletions

diff --git a/initrd.sh b/initrd.sh
index 5e7ed90..675dcc8 100755
--- a/initrd.sh
+++ b/initrd.sh
@@ -1,4 +1,18 @@
 #!/bin/sh
-set -ex
-cp -f /boot/vmlinuz-$(uname -r) isolinux/live/vmlinuz
-/usr/sbin/mkinitramfs -d initramfs-tools -o isolinux/live/initrd.img $(uname -r)
+
+initrd=isolinux/live/initrd.img
+vmlinuz=isolinux/live/vmlinuz
+
+conf_dir=initramfs-tools
+
+if [ ! -e "$initrd" -o ! -e "$vmlinuz" ]; then
+    need_update=1
+elif [ "$(find "$conf_dir" -newer "$initrd" -print -quit)" ]; then
+    need_update=1
+fi
+
+if [ "$need_update" ]; then
+    set -ex
+    cp -f /boot/vmlinuz-$(uname -r) "$vmlinuz"
+    /usr/sbin/mkinitramfs -d "$conf_dir" -o "$initrd" $(uname -r)
+fi
diff --git a/qemu.sh b/qemu.sh
index 2955c20..5c0abd2 100755
--- a/qemu.sh
+++ b/qemu.sh
@@ -1,7 +1,11 @@
 #!/bin/sh
 
 # img=debian-live-8.4.0-amd64-gnome-desktop.iso
-img=debian-live-8.4.0-amd64-standard.iso
+# img=debian-live-8.4.0-amd64-standard.iso
+img=debian-live-8.4.0-amd64-standard.btrfs.iso
+
+./initrd.sh
+
 sudo qemu-system-x86_64 -enable-kvm -smp 2 -m 640 -k en-us \
      -vga qxl \
      -net nic,vlan=0,model=virtio \