> I can also use it to construct a DVD image from my CDs.
So what am I missing here ? does jidgo really do a new buildinstall and
rerun hd-metadata in the distro ?
Lance just pointed out to me tht jidgo works using a rdiff like logic, which
makes sense I suppose.
To be precise it only actually cares about the files on a CD (ie. it
doesn't use the iso image - it uses the loopback-mounted iso image just
like if it was another directory on your hard disk).
Jigdo basically splits any (big) file into pieces which it can't find
anywhere (these it sticks in the template file), and the pieces which are
whole files taken from somewhere else (these then just get embedded as
ptrs in the jigdo/template combination with Base64 MD5 checksums to ensure
correctness). And the entire image is MD5 checksummed. So all the stuff
that is unique to the iso image (cd or dvd) ends up in the template (ie.
the iso directory structure, etc...).
For example based on the size of the jigdo template files you can guess
that while most of the centos/x.x/os/arch directories where copies of the
DVDs, the 4.4 i386 directory is a copy of the CDs. (you can tell this by
comparing the size of the template files for the CD DVD editions, smaller
means closer match). The CD and DVD editions are slightly different
because they differ in the locations of files on the media (ie. all on one
vs. all on many), so the file contents listing files are different.
Anyway - enough of this - I've been writing to much...
Maciej
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