#Version 0, written by Nick Fortino 
#March 23, 2009
#This has been tested only in chroot, bringing 2006.1-amd64-stage3 upto
#a stable amd64 system

#This is an experimental guide on how to upgrade an old system to get to
#portage 2.1.6.7. Once this state is achieved, portage can do the rest, with
#decent dependency resolution. 

###########################################################################
#Between the first tar command and the success of 'emerge -uDN system', the
#true state of the system, and the state according to portage are different.
#This is rather unsafe, so be sure you understand what you are doing.
#Consider this your big red warning to backup important files before attempting
#an update, and consider a re-install if possible.
###########################################################################

#It may be wise to use the default make.conf, as we would like to rebuild
#as few packages as possible before the toolchain has been updated, and use
#flags will bring in a bunch of dependencies

#Update the symlink to an existing profile
unlink /etc/make.profile
ln -s ../usr/portage/profiles/default/linux/amd64/2008.0 /etc/make.profile

#Fetch and forcefully upgrade python, bash, and portage with prebuilt sources
wget http://tinderbox.dev.gentoo.org/default-linux/amd64/dev-lang/python-2.5.2-r7.tbz2
wget http://tinderbox.dev.gentoo.org/default-linux/amd64/app-shells/bash-3.2_p39.tbz2
wget http://tinderbox.dev.gentoo.org/default-linux/amd64/sys-apps/portage-2.1.6.7.tbz2
cd /
tar xfpj root/python-2.5.2-r7.tbz2
tar xfpj root/bash-3.2_p39.tbz2
tar xfpj root/portage-2.1.6.7.tbz2

#remove the obsolete block from bash for portage; we got around it with a binary
#update (adding to /etc/portage/profile/package.provided would seem more 
#elegant, but doesn't work?)
cd /usr/portage/app-shells/bash
nano /usr/portage/app-shells/bash/bash-3.2_p39.ebuild
repoman manifest
cd /

#See what will be upgraded, there should be no unresolved blockers
emerge -puDNv system
#Perform the update, this command will likely make good progress, and then fail
emerge -uDN system

############
#Known failures and solutions
############

#Cracklib wants -unmerge-orphans
FEATURES='-unmerge-orphans' emerge -1 cracklib
#continue the upgrade
emerge -uDN system

#Python updater and python split, creating a confilct, resolve by removing
#the old file
rm /usr/sbin/python-updater
emerge -1 python-updater
#continue the upgrade
emerge -uDN system

############
#Cleanup
############

#Update the current terminal
env-update
source /etc/profile
#Deal with the many /etc files which need updating
emerge gentoolkit
dispatch-conf

#At this point, the toolchain has been rebuilt, which likely involved an upgrade
#of gcc. Follow http://www.gentoo.org/doc/en/gcc-upgrading.xml to finish the 
#upgrade. A lot of what is requested there has likely been done automatically,
#so in summary:

#Check that gcc-config is using the correct compiler, if not, follow the above
#guide
gcc-config -l

#Replace your make.conf/update to whatever profile you choose/etc.
#Rebuild the system with the new toolchain, and custom settings
emerge -eav system
#Rebuild and update world with new toolchain and settings
emerge -eav world

#Finally, remove any old packages which still survived the process
emerge --depclean -a