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Re: Introduction to a new SIG for creation of Live DVD



On 09/14/2009 03:48 PM, Andre Robatino wrote:
> On 09/14/2009 12:05 PM, John Reiser wrote:
>>> Deltaisos are capable of saving roughly half the download size in
>>> going from Fedora N to Fedora (N+1), but only work for installation
>>> images, not live images.  Is there any form of delta compression for
>>> live images which is competitive with this?
>>
>> It hasn't been productized, but approximately:
>>    unsquashfs  old-Live.img  old-Live.tree   # local  ("slave")
>>    unsquashfs  new-Live.img  new-Live.tree   # remote ("master")
>>    rsync  remote:new-Live.tree  local:old-Live.tree   # "delta
>> compression" happens here
>>    mksquashfs  old-Live.tree new-Live.img   # local
> 
> Has anyone tried this on existing live images to see how much is saved
> (say going from a Fedora N to Fedora (N+1) Live CD)?  I'm skeptical that
> rsync, which is completely general, would be as efficient as something
> specialized such as {make,apply}deltaiso.  It may be necessary for
> someone to create a specialized tool for delta compression between live
> images, in order to be able to compress as well as deltaisos currently
> do for the install images.

I tried doing this with the Live CDs for F10 and F11.  Almost the entire
content is in a single file LiveOS/squashfs.img.  Attempting to use
unsquashfs on this file gives

Parallel unsquashfs: Using 1 processor
FATAL ERROR aborting: failed to read fragment table

What am I doing wrong?  (I'm using the i686 live CDs.  I originally
tried it on an x86_64 host, then on an i686 host after reading somewhere
that might be the problem, but it made no difference.)


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