User:Hirotaka/Rasberry Pi

The Raspberry Pi is an ARM device (BCM2835, ARMv6) with 512 MB RAM (earlier models had 256 MB RAM) and uses an SD(HC) card for storage. This document describes how to install Gentoo on the Raspberry Pi.

Partitioning
Check that your SD card is compatible:

Create at least two partitions on the card. One FAT32 for the boot partition, and one (with your preferred filesystem) for the root partition:

For optimal compatibility, it is recommended to use 255H/63S geometry:

boot
The partition needs the following proprietary firmware files, provided by the Raspberry Pi foundation. If you want to be able to boot the board with the setting gpu_mem=16 in, you will also need these files: Create a file called containing the necessary kernel parameters. Example:

These are available as

Stage 3
Download the appropriate Stage 3:

Extract to the root filesystem on the SD card:

Don't forget to adjust fstab (the SD card is recognized as ) and add to the root password hash generated by:

Stage 4
If you'd prefer a self-booting Gentoo tarball (Stage 4), it can be downloaded from here. Please note this image is outdated and unmaintained however

NOOBS image. The NOOBS image will be created on a daily basis. I'd be pleased to get feedback... You can install NOOBS from here: https://github.com/raspberrypi/noobs and untar the NOOBS image from above in the OS folder (/os/Gentoo).

Portage tree
Download the latest portage tree:

Ensure you have enough inode blocks free on the root partition. Portage takes up approximately 154K.

Untar portage on the SD card:

crossdev
Install :

Create a cross toolchain for ARM: (drop -S if you plan to run an unstable system) (make sure you have defined PORTDIR_OVERLAY in your make.conf first):

If you get any errors or portage warnings here, please fix them. It takes a while until the cross toolchain is successfully set up, so go grab a coffee. :-)

Kernel and modules
Download kernel sources for Raspberry Pi from github

or

then configure, compile and install:

Raspberry Pi A, B, B+ (Not 2 B)
Create a file by

or using the Raspberry Pi mkimage tool from github:

That's it! You should all be set now.

Raspberry Pi 2 B
Just copy arch/arm/boot/zImage to /boot/kernel7.img

That's it!

Tips and Tricks

 * Storage is rather slow, even with the couple of compatible SDHC class 10 cards. If you want to run emerge on the Raspberry Pi, putting on squashfs will speed up things dramatically.
 * There is no hardware RTC on the Raspberry Pi. Use the ntp-client init script to set correct system time on boot. A fallback incremental clock can be archived by swclock (replaces hwclock).
 * If you require more RAM for Linux, set the option gpu_mem in config.txt. The smallest amount you can set is 16 MB, default is 64 MB
 * More recent, unofficial kernel releases for the Raspberry Pi might be found at Chris Boot's repository:
 * Be sure to test the performance - if your numbers don't match up (for instance in the LINPACK benchmark), something is very wrong.
 * For instructions on how to build binary packages for the Raspberry Pi on an Android phone see this blog post:
 * If you cannot create a working ARM cross-toolchain, a precompiled kernel image is available from the firmware repository. You need to place in your boot partition and copy the contents of the modules directory to  on the SD card.
 * Put the root-fs on a NFS-share and put only the kernel image on SD card (PXE boot client).

Troubleshooting

 * Problem: dmesg is full of smsc95xx 1-1.1:1.0: eth0: kevent 2 may have been dropped and/or page allocation failure messages
 * Solution: Try to update all firmware files in /boot, especially fixup.dat.
 * Solution if the former fails: Add smsc95xx.turbo_mode=N to kernel parameters, or vm.min_free_kbytes = 4096 to


 * Problem: the follwing error shows up when running the command
 * Solution: Try the following command instead:
 * Reference: https://forums.gentoo.org/viewtopic-t-946836-start-0.html

External resources

 * Gentoo Embedded Handbook with more information about embedded hardware, cross compiling and other related topics.
 * Raspberry Pi Hub at eLinux wiki, with more advanced tutorials to get the most out of your Raspberry Pi

Books

 * Heitz, Ryan. Hello! Raspberry Pi. Manning Publications (2015). pp. 225. ISBN 9781617292453