Raspberry 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.
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Preparing the SD card
Partitioning
Check that your SD card is compatible: [1]
Create at least two partitions on the card. One FAT32 for the boot partition, and one (with your preferred filesystem) for the root partition:
Disk /dev/sdb: 16.6 GB, 16574840832 bytes 255 heads, 63 sectors/track, 2015 cylinders, total 32372736 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x1db42224 Device Boot Start End Blocks Id System /dev/sdb1 * 2048 835379 416666 c W95 FAT32 (LBA) /dev/sdb2 835380 31889024 15526822+ 83 Linux /dev/sdb3 31889025 32372735 241855+ 5 Extended /dev/sdb5 31889088 32372735 241824 82 Linux swap / Solaris
For optimal compatibility, it is recommended to use 255H/63S geometry: [2]
boot
The /boot partition needs the following proprietary firmware files, provided by the Raspberry Pi foundation.
- bootcode.bin
- fixup.dat
- start.elf
If you want to be able to boot the board with the setting gpu_mem=16 in config.txt, you will also need these files:
- fixup_cd.dat
- start_cd.elf
Create a file called cmdline.txt containing the necessary kernel parameters. Example:
root=/dev/mmcblk0p2 rootdelay=2
Stage 3
Download the appropriate Stage 3:
root # wget http://distfiles.gentoo.org/releases/arm/autobuilds/current-stage3-armv6j_hardfp/stage3-armv6j_hardfp-YYYYMMDD.tar.bz2Extract to the root filesystem on the SD card:
root # tar xfpj stage3-armv6j_hardfp-YYYYMMDD.tar.bz2 -C /mnt/raspberrypiroot/
CFLAGS="-O2 -march=armv6j -mfpu=vfp -mfloat-abi=hard"
CXXFLAGS="${CFLAGS}"
Don't forget to adjust fstab (the SD card is recognized as /dev/mmcblk0) and add to /etc/shadow the root password hash generated by:
root # openssl passwd -1Stage 4
If you'd prefer a self-booting Gentoo tarball (Stage 4), it can be downloaded from here with install instructions here
Alternative dd image (update 04/30/2013).
Portage tree
Download the latest portage tree:
Ensure you have enough inode blocks free on the root partition. Portage takes up approximately 154K.
root # df -ih | egrep 'Mounted|mmc'Untar portage on the SD card:
root # tar xjvpf portage-latest.tar.bz2 -C /mnt/raspberrypiroot/usrCompiling the kernel
crossdev
Install sys-devel/crossdev:
root # emerge --ask crossdevCreate a cross toolchain for ARM: (drop -S if you plan to run an unstable system):
root # crossdev -S -v -t armv6j-hardfloat-linux-gnueabiIf 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 [3]
root # git clone --depth 1 git://github.com/raspberrypi/linux.gitthen configure, compile and install:
root # ARCH=arm make bcmrpi_cutdown_defconfig
root # ARCH=arm CROSS_COMPILE=/usr/bin/armv6j-hardfloat-linux-gnueabi- make oldconfig
root # ARCH=arm CROSS_COMPILE=/usr/bin/armv6j-hardfloat-linux-gnueabi- make -j2
root # ARCH=arm CROSS_COMPILE=/usr/bin/armv6j-hardfloat-linux-gnueabi- make modules_install INSTALL_MOD_PATH=/mnt/raspberrypiroot/Create a kernel.img file using the Raspberry Pi mkimage tool from github:
root # chmod a+x imagetool-uncompressed.py
root # ./imagetool-uncompressed.py arch/arm/boot/Image
root # cp kernel.img /mnt/raspberrypiroot/boot/That's it! You should all be set now.
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 /usr/portage 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 [4]
- More recent, unofficial kernel releases for the Raspberry Pi might be found at Chris Boot's repository: [5]
- 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: [6]
- If you cannot create a working ARM cross-toolchain, a precompiled kernel image is available from the firmware repository. You need to place boot/kernel.img in your boot partition and copy the contents of the modules directory to /lib/modules/ 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 /etc/sysctl.conf
- Problem: the follwing error shows up when running the command
root #crossdev -S -v -t armv6j-hardfloat-linux-gnueabi(...) configure: error: cannot compute suffix of object files: cannot compile (...)
- Solution: Try the following command instead:
root #CFLAGS="-O2 -pipe -march=armv6j -mfpu=vfp -mfloat-abi=hard" crossdev --stage3 -S -v -t armv6j-hardfloat-linux-gnueabi
- Solution: Try the following command instead:
See also
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
