When using Open Firmware to copy a new OS from a USB drive to the NAND FLASH or SD card, the process might stop and display the message:
Bad hash for eblock# <some number>
There are two likely causes:
- bad USB drive,
- corruption of download.
 Bad USB Drive
The usual cause is a bad USB drive that reads back different data from what you tried to write to it.
The solution is to use a different USB drive. Be sure to copy the files onto the new drive from a known good source - don't copy them from the bad drive to the new one, because that will just move the bad data to the new drive.
You can check the data on the USB drive before using it to update a laptop. Here is one way:
- Insert the USB drive in a laptop and start the Terminal activity, then type
$ md5sum /media/*/per703-4.img f8dcd6b011c6d54f8d09fac3fe155104 /media/7013/per703-4.img
- Compare the result with the contents of the corresponding ".md5" file (for example per703-4.img.md5) in the download directory.
 Corruption of Download
It is possible for the download to have been corrupted in some other way. Check the md5sum of the file, and if it does not match, download it again.