Avoid unnecessary initramfs rebuilds

Fixes a bug, plus adds a line of output that explains why a rebuild
was needed.

2 files changed, 13 insertions, 6 deletions

diff --git a/Makefile b/Makefile
index 4f75fe9..5596f5d 100644
--- a/Makefile
+++ b/Makefile
@@ -105,6 +105,8 @@ install-submodules-stamp: install-submodules
 install-bin-programs: ${bin_programs}
         install -p ${bin_programs} ${instdir}${samizdat_bindir}
 
+CP=cp --preserve=timestamps -r
+
 install-stamp: install-bin-programs samizdat-paths.sh ${compiled_programs}
         mkdir -p ${instdir}${samizdat_initrd_files_dir}
         mkdir -p ${instdir}${samizdat_child_dir}
@@ -112,7 +114,7 @@ install-stamp: install-bin-programs samizdat-paths.sh ${compiled_programs}
         mkdir -p ${instdir}${samizdat_initramfs_conf_dir}
         mkdir -p ${instdir}${samizdat_isolinux_dir}
         mkdir -p ${instdir}${samizdat_linux_dir}
-        cp -r ${initrd_files} ${instdir}${samizdat_initrd_files_dir}
-        cp -r ${initramfs_conf_files} ${instdir}${samizdat_initramfs_conf_dir}
-        cp -r ${isolinux_files} ${instdir}${samizdat_isolinux_dir}
+        $(CP) ${initrd_files} ${instdir}${samizdat_initrd_files_dir}
+        $(CP) ${initramfs_conf_files} ${instdir}${samizdat_initramfs_conf_dir}
+        $(CP) ${isolinux_files} ${instdir}${samizdat_isolinux_dir}
         touch $@
diff --git a/src/initrd.sh b/src/initrd.sh
index b99aa4e..1414c89 100755
--- a/src/initrd.sh
+++ b/src/initrd.sh
@@ -19,7 +19,8 @@ force_rebuild()
 
 rebuild()
 {
-    [ ! -f "$apt_dependencies" ] || sudo apt-get install -q=10 --no-upgrade -y $(cat "$apt_dependencies")
+    [ ! -f "$apt_dependencies" ] ||
+        sudo apt-get install -q=10 --no-upgrade -y $(cat "$apt_dependencies")
 
     set -ex
     cp -f /boot/vmlinuz-"${kernel_version}" "$vmlinuz"
@@ -30,6 +31,10 @@ rebuild()
 
 if [ ! -e "$initrd" -o ! -e "$vmlinuz" ]; then
     rebuild
-elif [ "$(find_source_dirs -newer "$initrd" -print -quit)" ]; then
-    rebuild
+else
+    found=$(find_source_dirs -newer "$initrd" -print -quit)
+    if [ "$found" ]; then
+        echo "initrd.sh: rebuild forced: found modified source: $found"
+        rebuild
+    fi
 fi