I'm in the process of re-installing a pretty old machine with the latest Gentoo. I've got a shared NFS directory with portage and all my machines are using a packages directory. After one machine builds something, another machine can simply install the built package.
Here is a portion of the make.conf on each machine.
Well, this particular machine was installed with Glibc 2.3.x. I typed the following to do the upgrade:
emerge -auDvk system
About 1/3 of the way through the upgrade, tar suddenly stopped working:
tar: /lib/libc.so.6: version `GLIBC_2.4' not found (required by tar)
I realized that tar had been upgraded but the glibc was not yet upgraded. To fix the problem, I created a new version of tar on a different system:
USE="static" emerge -av tar # on another machine
Off I go, things are working.