I’m currently setting up a server to migrate an older one to. In order to emerge all necessary ebuilds I basically took the worldfile of the older one, sorted, diffed and edited it to finally emerge `cat mergelist` it on the new system. Except for a few dependency problems (emerge --resume --skip-first and later reruns fixed those) everything went fine. Unfortunately, having emerged maildrop, it blocked the installation of courier-imap due to file collisions:
* This package will overwrite one or more files that may belong to other * packages (see list below). You can use a command such as `portageq * owners /` to identify the installed package that owns a * file. If portageq reports that only one package owns a file then do * NOT file a bug report. A bug report is only useful if it identifies at * least two or more packages that are known to install the same file(s). * If a collision occurs and you can not explain where the file came from * then you should simply ignore the collision since there is not enough * information to determine if a real problem exists. Please do NOT file * a bug report at http://bugs.gentoo.org unless you report exactly which * two packages install the same file(s). Once again, please do NOT file * a bug report unless you have completely understood the above message. * * Detected file collision(s): * * /usr/bin/maildirmake * /usr/share/man/man1/maildirmake.1.bz2 * /usr/share/man/man8/deliverquota.8.bz2 * * Searching all installed packages for file collisions... * * Press Ctrl-C to Stop * * mail-filter/maildrop-2.2.0 * /usr/bin/maildirmake * /usr/share/man/man1/maildirmake.1.bz2 * /usr/share/man/man8/deliverquota.8.bz2 * * Package 'net-mail/courier-imap-4.5.0' NOT merged due to file * collisions. If necessary, refer to your elog messages for the whole * content of the above message.
maildrop belongs to courier and although that collision isn’t great but won’t hurt being ignored, I added the following line to /etc/make.conf (wrapped to be readable on my blog):
COLLISION_IGNORE="/usr/bin/maildirmake \ /usr/share/man/man1/maildirmake.1.bz2 \ /usr/share/man/man8/deliverquota.8.bz2"
This will permanently ignore the collision for all 3 files.