Most of the instructions are as described on the cern twiki

https://twiki.cern.ch/twiki/bin/view/Atlas/WorkBookInstallingAtlasSoftware

but some specifics (so I use bash):

export PATH=/usr/nevis/gcc-3.4.6/bin:${PATH}

pacman -pretend-platform SLC-4 (this needs to be done after creating the directory for the release, but before the pacman -get)

then

pacman -allow tar-overwrite trust-all-caches -get am-BNL:xx.xx.xx

-- GustaafBrooijmans - 04 Mar 2008