short read of zdata file

James Cameron quozl at
Wed Jan 11 16:05:01 EST 2012

On Wed, Jan 11, 2012 at 12:51:48AM -0800, Sameer Verma wrote:
> I'm seeing a "short read of zdata file" on running fs-update on a 1.75
> using os23.zd4
> Any suggestions?

Reflash to the current firmware.  For an XO-1.75 B1, that is Q4C12.

Then try again.

If the problem persists, then consider this explanation.

The zdata file, the os23.zd4 file, contains block headers then block
data.  Each block header describes the length of data that follows.  If
the length is shorter than the remaining length of the file at that
point, you get "Short read of zdata file".

The most likely causes of this message are:

1.  the file is missing data from the end, usually caused by incomplete
download, so check the file size is 766009232 bytes, and if it is less
then resume the download from where it left off, see for methods,

2.  the file has a corrupted block header, usually caused by corruption
during download, so check the md5sum is
26c565b19c1b5465c421183cdd771546, and if it is incorrect then correct it
using one of the methods at

3.  the USB drive could not be read by OpenFirmware, resulting in a
premature close of the file ... if so there should be some preceeding
message, please report it.  Otherwise, try using OpenFirmware to read
the file and copy it, then check the copy with another computer, e.g.

	ok copy u:\os23.zd4 u:\copy.zd4

James Cameron

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