[Testing] Dextrose Install Snags

[Mitch Bradley]

On 9/12/2010 4:12 PM, Caryl Bigenho wrote:
>
> Hi...
>
>
> 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?

>
> 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 different.
>

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.
>
>
> Thanks,
>
>
> Caryl
>
>
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