[IAEP] [Testing] Dextrose Install Snags

Caryl Bigenho cbigenho at hotmail.com
Sun Sep 12 23:09:17 EDT 2010

Date: Sun, 12 Sep 2010 16:41:34 -1000
From: wmb at laptop.org
To: cbigenho at hotmail.com
CC: testing at lists.laptop.org; iaep at lists.sugarlabs.org; support-gang at laptop.org
Subject: Re: [Testing] Dextrose Install Snags




    On 9/12/2010 4:12 PM, Caryl Bigenho wrote:

      I was trying to
          install Dextrose on an XO-1.5 today.  I was following the
          instructions on:   http://wiki.sugarlabs.org/go/Dextrose
      There was only one
          file listed to download for the XO-1.5 : os373pyg.zd.  I
          followed the directions on the page and got an error message
          that the file was all in "one chunk"

    at which step in the directions did the error message appear?
The message appears after entering " fs-update u:\os373py.zd  at the "ok" prompt.
The machine is unsecured. All of the XO-1s I have have Developer Keys.  Am I correct that a Developer Key is not needed for the XO-1.5?


      So I am trying to do
          it for an XO-1 instead.  However, I notice that while there
          are two files for the XO-1, the .img file and the .crc file,
          there is only one for the XO-1.5, the .zd file.

      When I installed 852
          on both types of machines, there were 2 files for each.  Is
          there a file missing on the Dextrose page listed above?  Can I
          just use the fs.zip file from 852?

      While I am asking, is
          there a reason why the files for the XO-1 for 852 are .img and
          fs.zip while those for Dextrose are .img and .crc?  I am not a
          whiz on file types so I haven't a clue why these would be

    fs.zip is a security bundle, needed only for updating a system with
    security enabled.  fs.zip does not contain any actual filesystem
    data; instead, it contains a much-shorter list of hash values that
    represent the actual data, and a signature that authenticates that
    hash list.


    fs.img is for XO-1 only.  It contains raw data that goes verbatim
    into the internal NAND FLASH inside the XO-1.


    fs.crc, for XO-1 only, contains a list of check values that
    represent the data in fs.img.  Its purpose is to catch corrupted
    fs.img files, which sometimes happen due to download problems or USB
    stick errors.  The checksum algorithm in fs.crc (CRC-32) is much
    weaker than the hash algorithm used in fs.zip.  CRC-32 is good
    enough to catch accidental file corruption, but not strong enough to
    prevent a determined attack.


    fs.zd is a new format that was introduced for XO-1.5.  It combines
    checking (via the strong hash code) and the actual filesystem image
    data in one file, with explicit compression to shrink the file to a
    manageable size.  It was necessary to come up with a new format
    because XO-1 and XO-1.5 have very different internal storage.  XO-1
    uses raw NAND FLASH that is formatted with the JFFS2 filesystem
    layout, while XO-1.5 uses a micro-SD card that emulates a hard disk,
    formatted with the same ext2/ext4 filesystem layout.  JFFS2
    filesystem data is already internally compressed, so there is no
    need for explicit compression.  That is not the case for ext2
    filesystem data, so the compression had to be explicit in the .zd
    file format.


    The fs.zip files for XO-1 and XO-1.5 are similar, but not
    identical.  For XO-1, fs.zip contains hash values suitable for
    checking fs.img.  For XO-1.5, fs.zip contains hash values too, but
    their format is different, being suitable for checking fs.zd.



      I need to get this
          done in time for a "show and tell" at Montana State University
          on Thursday morning.


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