install-header:changed dd extraction block size

Previously, we extracted block=1B * sizeof(chunk). This was extremely
slow. Changing block size to sizeof(chunk) and count to 1, the process
is sped up by about 200x.

1 files changed, 3 insertions, 1 deletions

diff --git a/install-header.sh b/install-header.sh
index a7b9269..b54a0ec 100755
--- a/install-header.sh
+++ b/install-header.sh
@@ -8,6 +8,8 @@ export SELF       # Absolute path to the installer script (me!)
 export TMP        # Path to tmp install staging directory
 export PAYLOAD    # Path to the extracted payload directory
 export NOCLEANUP  # Do not clean up deploy resources. Useful for debugging
+export COMPRESS   # Command to compress data
+export DECOMPRESS # Command to decompress data
 
 # Header:    0
 # runscript: 1
@@ -25,7 +27,7 @@ extract_chunk_index() {
 
   [ "${dest}" != '-' ] && of="of=${dest}"
   # Extract the requested chunk index
-  dd bs=1 count=${LENS[$index]} iflag=skip_bytes skip=${skip} \
+  dd bs=${LENS[$index]} count=1 iflag=skip_bytes skip=${skip} \
     if=${src} ${of} 2>/dev/null
 }