Raspberry Pi/Quick Install Guide

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Installing Gentoo onto a Raspberry Pi is relatively straight forward and in some ways easier than installing Gentoo on another system because a kernel image is provided by the Raspberry Pi Foundation. This means Gentoo can be quickly installed quickly onto a Raspberry Pi.

This quick install guide presumes the reader will be installing from a Linux based operating system.

Preparing the SD card

The Raspberry Pi boots off a FAT32 /boot partition. It will also require root and swap partitions.

Create the partitions

Use the fdisk utility to create the partitions:

root # fdisk /dev/mmcblk0
Example partitioning scheme

Disk /dev/mmcblk0: 7948 MB, 7948206080 bytes
4 heads, 16 sectors/track, 242560 cylinders
Units = cylinders of 64 * 512 = 32768 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000635b7

        Device Boot      Start         End      Blocks   Id  System
/dev/mmcblk0p1               1        3201      102424    c  W95 FAT32 (LBA)
/dev/mmcblk0p2            3202        7298      131104   82  Linux swap / Solaris
/dev/mmcblk0p3            7299      242560     7528384   83  Linux

Create the file systems

root # mkfs.vfat -F 16 /dev/mmcblk0p1
root # mkswap /dev/mmcblk0p2
root # mkfs.ext4 /dev/mmcblk0p3

When using a 4GB SD card:

root #mkfs.ext4 -N 803200 /dev/mmcblk0p3


The installation will be preformed onto the SD card.

Mounting the partitions

root # mkdir /mnt/gentoo
root # mount /dev/mmcblk0p3 /mnt/gentoo
root # mkdir /mnt/gentoo/boot/
root # mount /dev/mmcblk0p1 /mnt/gentoo/boot

Extract stage 3 image

root # cd /tmp/
root # wget http://gentoo.osuosl.org/releases/arm/autobuilds/current-stage3-armv6j_hardfp/stage3-armv6j_hardfp-20130816.tar.bz2 (Change the date for the latest or required stage.)
root # tar xfpj stage3-armv6j_hardfp-*.tar.bz2 -C /mnt/gentoo/

Install Portage

root # tar xjf portage-latest.tar.bz2 -C /mnt/gentoo/usr

Install kernel and modules

The Raspberry Pi Foundation maintains a branch of the Linux kernel that will run on the Raspberry Pi, including a compiled version which we use here:

root # cd /tmp/
root # git clone --depth 1 git://github.com/raspberrypi/firmware/
root # cd firmware/boot
root # cp * /mnt/gentoo/boot/
root # cp -r ../modules /mnt/gentoo/lib/


Edit fstab

Edit the /etc/fstab file to match the previously created partition scheme:

root # nano /mnt/gentoo/etc/fstab
FILE /etc/fstabExample
/dev/mmcblk0p1		/boot		auto		noauto,noatime	1 2
/dev/mmcblk0p3		/		ext4		noatime		0 1
/dev/mmcblk0p2		none		swap		sw		0 0

Set boot options

Create a file called cmdline.txt in /boot to pass options to the kernel:

root # nano /mnt/gentoo/boot/cmdline.txt
FILE /boot/cmdline.txt
dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p3 rootfstype=ext4 elevator=deadline rootwait

Edit make.conf

The default make.conf includes basic CFLAGS. To change the settings to something more 'optimal' for the Pi look at the details on the relevant wiki page.

Configure time zone

View a list of time zones using this command:

root # ls /mnt/gentoo/usr/share/zoneinfo

Choose the appropriate time zone. Note that some of the listings in the zoneinfo directory are folders that contain more specific time zones. For example, supposing Europe/London is the local time zone:

root # cp /mnt/gentoo/usr/share/zoneinfo/Europe/London /mnt/gentoo/etc/localtime

Next set the timezone:

root # echo "Europe/London" > /mnt/gentoo/etc/timezone

Clear root password

As chroot was not performed before booting, the root password needs to be unset. Allowing login with a blank password for the root user.

root # nano /mnt/gentoo/etc/shadow

Edit the line for root so it looks like the example below.

FILE /etc/shadow

Unmount the SD card and boot the Raspberry Pi

Unmount the SD card:

root # umount /mnt/gentoo/boot
root # umount /mnt/gentoo

Plugin the SD card to the Raspberry Pi, make sure there is a keyboard and monitor plugged in, then connect the power supply. Hopefully Gentoo will boot displaying a login prompt, login as root and no password. During the first boot there could be a few warnings and errors which can be fixed in the next section.

Post boot configuration

Set root password

Immediately set a root password:

root # passwd

Enabling networking on boot

Assuming the use of DHCP on the eth0 network interface.

NOTICE: Now copy net.lo, a symlink doesn´t work!

root # cd /etc/init.d/
root # cp net.lo net.eth0
root # rc-config start net.eth0
root # rc-update add net.eth0 boot

Please also note that rc-update may need to be run, as follows

root # rc-update --update

to force an update of the dependency tree. This may be needed in the event of clock skew (in this specific case the eth0 device will not start up after reboot).

Select profile

List the available profiles.

root # eselect profile list

Select the desired profile, for example [25] default/linux/arm/13.0/armv6j:

root # eselect profile set 25

Configuring inittab and rc.conf

Uncomment the linux specific rc.conf rc_sys value, to stop warning in boot up.

root # nano /etc/rc.conf
FILE /etc/rc.conf

Comment out the s0 Serial console to stop "INIT: Id "s0" respawning too fast" messages on the console.

root # nano /etc/inittab
FILE /etc/inittab
#s0:12345:respawn:/sbin/agetty 9600 ttyS0 vt100
#s1:12345:respawn:/sbin/agetty 9600 ttyS1 vt100

Enable software clock

The Raspberry Pi does not have a hardware clock, so the hwclock daemon needs to disabled, then swclock can be enabled to mitigate the issue.

root # rc-update add swclock boot
root # rc-update del hwclock boot

The date still needs to be set beforehand to install any package, or in the compiling phase there could be warnings about clock skew. Check system time using date command.

root # date
Thu May 02 04:21:18 UTC 2013

If the date/time displayed is wrong, update it using the date MMDDhhmmYYYY syntax (Month, Day, hour, minute and Year). At this stage, the timezone that was set before in the Configure time zone section should be used. For instance, to set the date to May 02th, 04:21 in the year 2013:

root # date 050204212013

Now it is possble to set the system time using NTP software to setup the system clock on boot.

root #emerge --ask ntp
root # rc-update add ntp-client default

Enable SSH Daemon

root # rc-update add sshd default
root # /etc/init.d/sshd start


It is very easy to overclock a Raspberry Pi up to 1000MHz without affecting the warranty [1]

Suggested overclocking values

#“None” “700MHz ARM, 250MHz core, 400MHz SDRAM, 0 overvolt”
#“Modest” “800MHz ARM, 300MHz core, 400MHz SDRAM, 0 overvolt”
#"Medium” “900MHz ARM, 333MHz core, 450MHz SDRAM, 2 overvolt”
#“High” “950MHz ARM, 450MHz core, 450MHz SDRAM, 6 overvolt”
#“Turbo” “1000MHz ARM, 500MHz core, 500MHz SDRAM, 6 overvolt”

Enabling Overclocking

To enable overclocking select one of the suggest modes from the list above, "Medium" is generally a good starting point. Edit the /boot/config.txt, add the appropriate values and reboot the Raspberry Pi for changes to take effect.

root # mount /boot/
root # nano /boot/config.txt
FILE /boot/config.txtExample with Medium overclocking

Optional cpupower

To manage the CPU frequency scaling, use the sys-power/cpupower.

root #emerge --ask sys-power/cpupower
root #rc-update add cpupower default

The default scaling governor can be changed in the /etc/conf.d/cpupower file

FILE /etc/conf.d/cpupowerExample config with on demand scaling
START_OPTS="--governor ondemand"
STOP_OPTS="--governor performance"

Confirm the current scaling and CPU using the cpupower command

root # cpupower frequency-info

Force Turbo Option

The force turbo option turns off the dynamic clocks and runs the Raspberry Pi constantly at the highest arm_freq. [2] Edit the /boot/config.txt, add force_turbo=1 then reboot the Raspberry Pi for changes to take effect.

root #nano /boot/config.txt
FILE /boot/config.txtExample with Medium overclocking and force turbo

Changing memory split

Not strictly speaking overclocking, but the memory used by the GPU can be changed. To change the memory used by the GPU down to a minimum of 16MB add the gpu_mem value to /boot/config.txt, then reboot the Raspberry Pi for changes to take effect.

FILE /boot/config.txtExample with the minimum 16MB of memory for GPU

Cross building (Optional)

This is not strictly required, but it is extremely practical given the source driven nature of Gentoo. Building almost anything on the Raspberry Pi takes a very, very long time - especially when there are a lot of dependencies involved.

Fortunately, much of the heavy lifting work can be offloaded to a more powerful system (such as a another gentoo desktop/server) using crossdev and distcc (though this will only work for packages must compile c/c++).

Full details of using distcc and crossdev on the Raspberry Pi are described in Raspberry Pi Cross building.

Hardware Random Number Generator

The Arch Wiki tells us that the Raspberry Pi has a hardware random number generator.[1]

Hooking it up to /dev/random is done via the following steps.

Install rng-tools

root #emerge -av sys-apps/rng-tools

Load bcm2708-rng

root #modprobe bcm2708-rng

Apply settings in /etc/conf.d/rngd

Add the following to /etc/conf.d/rngd

FILE /etc/conf.d/rngd
RNGD_OPTS="-o /dev/random -r /dev/hwrng"

Check that /dev/random is slow

To verify that we have done everything correctly, open a new terminal and do:
user $cat /dev/random
It will start displaying gibberish (random) but will stop at some point or at least slow down. Now issue CTRL+C to stop it.

Restart rngd

root #/etc/init.d/rngd restart

Test if it works

Again, issue:
user $cat /dev/random
in another terminal. Now the random information should be flowing faster than the first time around. Now issue CTRL+C to stop it.

On an idling Pi (networked via a Wi-Fi USB dongle, a USB keyboard attached, display connected) /dev/random spews 4-5 "chars" of random information before it blocks. After loading the module and starting rng-tools, it began printing out many lines without blocking.

Add rng-tools to boot

If all is good, add rngd to boot.

root #rc-update add rngd boot

Add loading of bcm2708-rng to boot

Add the following to /etc/conf.d/modules so that the module gets loaded at boot

FILE /etc/conf.d/modules

Install Video Core Userland tools and libraries

The ARM side libraries for interfacing to Raspberry Pi GPU are included in a package raspberrypi-userland. Which includes the Video Core tools, GLES2, EGL, openmax and openVG libs that support the Raspberry Pi GPU.

root #emerge --ask raspberrypi-userland

Then optionally add the following to the shellrc (.bashrc/.zshrc) file to be able to call things like vcgencmd directly.

FILE ~/.bashrc
export PATH=$PATH:/opt/vc/bin

Notes and references

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 the Raspberry Pi