OLPC bad hash for eblock problem when upgrading

Your OS image (e.g. os767.img) that you want to upgrade to is corrupted from either being downloaded improperly or copied to your usb drive improperly. For me it was the latter.

Use the md5sum command to compare the file you have copied to your usb drive to the one on the olpc website (md5 sum file is also on the olpc website so you can compare).

If, like me, your file was getting corrupted moving from your desktop where you downloaded the file to your usb drive, try both of the following in sequence.

1) mount the usb drive with the sync option (under gnome 2.24 or newer you can get to this in the drive properties dialog under mount options -- type sync there and remount the device). Note that this option produces more wear on flash drives, and should be turned off after you successfully flash your olpc. On the other hand, if you are regularly getting large files with bits corrupted, especially on a cheap flash drive that you are not worried about, might not be that bad to leave it on.

2) use the cp command from the commandline rather than dragging the file to the usb drive from gnome, it doesn't cheat to make the copying seem faster.