This method uses a NOOBS install of Raspbian as the host to install Gentoo onto a USB Hardrive. It is quick, simple providing a working Gentoo install with the least pain in the shortest time possible.
Most important of all, this method is pretty safe (In theory). Should anything go wrong, you can simply reboot with Raspbian to do repairs or maintence. Because this is a dual boot setup. If things go really badly wrong, NOOBS can rescue the bootloader and re-install Raspbian. While I have taken every precaution I could think of, please be aware that installing any operating system is not with out risk.
It is easier and faster than you might think. One of the reasons it is quick and easy, is that it uses the Raspberry Pi Foundation Kernel by simply pulling it from GIT. No Kernel Compile required.
You'll also end up with a machine theoretically fractionaly faster because it everything will be compiled for ARMv7a_hardFP unlike other distros which are all compiled for ARMv6. So this install is only for a Raspberry 2 with NOOBS and Raspbian. Most important, you will get a customized install of exactly how you think it Linux should be installed.
What follows is How I Did It .... Every instruction has been copy pasted directly from my install. I then re-installed a couple of times following and these instructions to check they are "correct". That said, it probably contains some minor errors. I am not a Gentoo Developer nor do I claim to be a Linux Guru. I did this because I wanted Gentoo on a Raspberry without burning holes on an SD Card or being left with an un-bootable brick. I post this with no Warranty, because I want to help other people. If you spot mistakes or can suggest improvements, please contact evadinggrid AT yandex.
The install falls roughly into 3 catagories or stages.
That is the basic out line of the install. At no point does it make large demands on the compiler, nor does it take very long to complete.
It is trivial to purchase a suitable SD Card with NOOBS pre-installed. It is also wise, as not all SD Cards are created equal. This method demands NOOBS, as we will use at as an effective replacement for Grub/LILO.
This might look intimidating, but many of these steps only require you copy paste one or two lines. Some steps are just double checking, or informational.
Instead of copy pasting, those people who followed the default partioning and formating scheme and know what they are doing can use this very simple script instead. Read it before using it, and do not use it if you do not understand it. It starts at step 5 mounting the USB drive and stops at step 11 after preparing the chroot enviroment. Because of the possible danger of script mounting and formatting drives, the first part is commented out....
Configure Gentoo from inside a Gentoo chroot jail
Have you backed up all your data yet ?
This install relies upon NOOBS, more comprehensive documentation, including more advanced configuration of NOOBS, is available on GitHub.
I am not, nor ever will be, an elite gentoo hacker or developer. I will never make it as a Technical Author either, being dsylexic with tendencies to aspergers and the social skills of a Ferengi does not help either. So for definative correct information about all things Gentoo vist the website https://gentoo.org/ and take time to read the documentation (RTFM).
For more information, Gentoo has handbooks on Working with Gentoo, Working with Portage and Network configuration. You really should take at least a 5 minute look at the documentation before even considering an install.
Gentoo is nothing like Linux Mint, it is a source based meta linux. It is important to realise, that things like a Working Desktop are not provided by this install. This install will only provide a minimal, raw, tiny, crude, gentoo environment - from which YOU can config and build what ever you want.
Now go away, sleep on it, and then if you still want to have a go, re-read the instructions, back up everything, and follow the instructions with the Offical Gentoo Handbook to hand - so that you can see the steps I skipped in an effort to simplify the install.
Spot the oxymoron....
The Mac is harmless, everything just works. Windows mostly harmless because they think config means clicking in control panel. Mint is deadly because of package dependency hell, and a flawed release system. Gentoo is down right dangerous, because it is not a toy. Only Linux From Scratch is Elite, and thats the truth of it... LOL :-)