diff --git a/fpga/NOTES.md b/fpga/NOTES.md
index 12f96a4..a3dc55e 100644
--- a/fpga/NOTES.md
+++ b/fpga/NOTES.md
@@ -3,3 +3,11 @@ Wed, 06 Mar 2024 11:38:08 +0100
 Only /dev/console seems to output anything. We need to patch stage1 so it
 doesn't use the console from bootcmd. Or specify boot.debug1 before the
 console=hvc0 argument.
+
+Thu, 07 Mar 2024 16:53:28 +0100
+
+To patch the initrd disk (typically a cpio file compressed with gzip) use the
+following commands:
+
+$ cpio -idv < ../initrd.cpio
+$ find . | cpio -o -H newc > ../initrd2.cpio