add docs for writing media

README.md

@@ -66,6 +66,18 @@ make attest
 make sign
 ```
 
+## Provisioning ##
+
+1. Write airgap.iso to CD-ROM or SD Card
+  a. `dd if=out/airgap.iso of=/dev/sda bs=1M conv=sync status=progress`
+  b. `cdrecord out/airgap.iso`
+
+2. Verify media still produces expected hash
+  ```
+  sha256sum out/airgap.iso
+  head -c $(stat -c '%s' airgap.iso) /dev/sda | sha256sum
+  ```
+
 ## Setup ##
 
 Assumes target is running Pureboot or Coreboot/heads