effect of xz compression change on deltaiso users

[Andre Robatino]

As of Fedora 15, xz compression has changed - see

http://lists.fedoraproject.org/pipermail/devel/2010-October/144651.html


Versions of Fedora <= 14 continue to use the old compression, but
everything after that (including Rawhide and the current Branched 15)
will use the new compression. To use applydeltaiso successfully on a
diso which goes from oldiso to newiso, the system must be using the
compression corresponding to newiso. For example, a diso for 13->14
requires the old compression, but a diso for 14->15 will require the new
compression. This means that it won't be possible to just use a 14->15
diso, or any of the disos for F15 development, on a standard F14 system.
It can be done on a F15 or Rawhide system, of course, but this is a
Catch-22 for people who want to install F15 from the DVD. It's possible
to temporarily modify a F14 system to use the new compression. First,

1) Run "rpm -q xz xz-devel xz-libs xz-lzma-compat xz-debuginfo" to find
which xz binary packages are currently installed. Then go to
http://koji.fedoraproject.org/koji/buildinfo?buildID=219464
(xz-5.0.1-2.fc15) and download the corresponding RPMs for the correct
arch (either i686 or x86_64). In addition, download the xz-compat-libs
RPM for the same arch.

2) Run "rpm -q deltaiso deltarpm drpmsync python-deltarpm
python3-deltarpm deltarpm-debuginfo" to find which deltarpm binary
packages are currently installed. (If you do not already have the
deltaiso package installed, install it from the F14 repo.) Then go to
http://koji.fedoraproject.org/koji/buildinfo?buildID=202380
(deltarpm-3.6-0.4.20100708git.fc15) and download the corresponding RPMs
for the correct arch.

In the following example modification, I'm assuming a x86_64 F14 system
with xz, xz-libs, deltaiso, deltarpm, and python-deltarpm installed.

---

1) First use yum shell (man yum-shell) to install/update the xz
packages, using the following sequence of commands (adjust the "update"
command depending on the currently installed packages):

config gpgcheck 0
install xz-compat-libs-5.0.1-2.fc15.x86_64.rpm
update xz-5.0.1-2.fc15.x86_64.rpm xz-libs-5.0.1-2.fc15.x86_64.rpm
run
exit

2) Update the deltarpm packages (again, adjust depending on currently
installed packages):

yum --nogpgcheck update deltaiso-3.6-0.4.20100708git.fc15.x86_64.rpm
deltarpm-3.6-0.4.20100708git.fc15.x86_64.rpm
python-deltarpm-3.6-0.4.20100708git.fc15.x86_64.rpm

---

At this point, your system will be using the new compression, so
applydeltaiso will work on disos for F15 and later. HOWEVER, yum-presto
in F14 needs the old compression for deltarpms to rebuild properly
(otherwise it falls back to downloading full RPMs), so when done
rebuilding the diso, reverse the modification as follows:

---

1) First downgrade the deltarpm packages to the original F14 versions
with the following command (adjust depending on currently installed
packages):

yum downgrade deltaiso deltarpm python-deltarpm

2) Use yum shell to remove/downgrade the xz packages to the original F14
versions, with the following sequence of commands (adjust the
"downgrade" command as needed):

remove xz-compat-libs
downgrade xz xz-libs
run
exit

---

Note that in the special case of DVD->netinst disos, which compression
is being used doesn't matter (since these particular disos don't
actually contain any deltarpms), so this modification isn't necessary.
But for the much larger DVD->DVD disos, it is (when the newer ISO is F15
or later).

If this modification is attempted with F13 or below, there may be
trouble - I tried it on F13 and would have had to remove python-deltarpm
and a few packages depending on it on order to be able to do the
deltarpm update (there was a python dependency preventing it from
working otherwise). This is not too big a deal, since the packages can
be reinstalled afterwards. In any case, most people interested in F15 or
above are probably already running at least F14.

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