RaspberryPi - Install Gentoo (headless)

After buying a Raspberry Pi for home automation and a building a little home server, I decided to install again Gentoo as my favorite OS. There a lot of Tutorials out there which handles this topic. Also there are some of them that describe the steps to do for a working installation without monitor and keyboard. So, I want to thank all the contributors, blog an howto writers that have inspired me to write this one. Even if I try to comment every step in detail, this is more like a Todo list for myself.

Like my predecessors, I had to this time neither a HDMI enabled monitor, or keyboard or mouse available. Only my laptop which is running on Gentoo-amd64 and I was thus forced to cross compiling. But because the Raspi was indeed designed to preserve resources and thus not exactly shine with performance during the compile, it is generally a good idea to pre-compile packages on a more powerful computer and then copy.

Attention: Using the following steps to create a Gentoo based Raspberry Pi box assumes to have some advanced Linux, Gentoo and Portage experience. Also some basic operating system knowledge is needed. Be careful if you are no expert and you do not know what a single step matters, do not just copy, paste and execute it!

Prepare SD card

As first step "fdisk" is needed for partitioning. I also used the recommendation for heads, sectors and cylinders @eLinux - RPi Advanced Setup. Afterwards my SD card partition table looks like this: 
    
        Device          Boot     Start      Ende  Blocks  Id    System
        /dev/mmcblk0p1  *        2048    104447   51200   c     W95 FAT32 (LBA)
        /dev/mmcblk0p2         104448   1128447  512000  82     Linux swap / Solaris
        /dev/mmcblk0p3        1128448  15546367 7208960  83     Linux
Because this was my first "Raspi" try, I used the SD Card as swap device too. But concerning the write limitation of NAND flash based drives, it should be moved to another device later.

Format SD card

In my next step, the SD card partitions had to be formatted:
    
        mkfs.vfat -F 16 /dev/mmcblk0p1
        mkfs.ext4 /dev/mmcblk0p3 # IF USING 4GB SD Card: -N 803200
        mkswap /dev/mmcblk0p2
As already said, this was my first setup, so I decided to ext4 as root file system. F2FS or another NAND flash optimized system should be recommended for a longer lifetime. It might also be a good idea to move the some directories to other devices, like /tmp, /var, /home to reduce writing access.

Download

So far so good, now I had to download and install the stage3 arm release, as also the latest portage tree.
        
        cd /home/myuser/Downloads/raspberrypi
        wget -c http://ftp.uni-erlangen.de/mirrors/gentoo/releases/arm/autobuilds/current-stage3-armv6j_hardfp/stage3-armv6j_hardfp-20140818.tar.bz2
        wget -c http://distfiles.gentoo.org/snapshots/portage-latest.tar.bz2

Mount, copy, extract & (cross)-compile

I used two separate directories to mount my SD card partitions and extracted the archives into them:
    
        mount /dev/mmcblk0p3 /mnt/gentoo
        mount /dev/mmcblk0p1 /mnt/gentooboot
        cp portage-latest.tar.bz2 portage-latest.tar.bz2.backup
        cp stage3-armv6j_hardfp-20140818.tar.bz2 stage3-armv6j_hardfp-20140818.tar.bz2.backup
        tar xfpj stage3-armv6j_hardfp-*.tar.bz2 -C /mnt/gentoo
        tar xjf portage-latest.tar.bz2 -C /mnt/gentoo/usr
To compile the kernel by a "foreign" architecture, cross compile tool chain is needed, see references for links and additional information. After the challenge to get the tool chain running correctly, it was quite easy to compile the kernel on my amd64 based laptop:
    
        cd /usr/src/linux-3.16.9999-raspberrypi
        make ARCH=arm bcmrpi_defconfig 
        make ARCH=arm CROSS_COMPILE=/usr/bin/armv6j-hardfloat-linux-gnueabi- oldconfig
        make ARCH=arm CROSS_COMPILE=/usr/bin/armv6j-hardfloat-linux-gnueabi- -j2
        make ARCH=arm CROSS_COMPILE=/usr/bin/armv6j-hardfloat-linux-gnueabi- modules_install INSTALL_MOD_PATH=/mnt/gentooimagetool-uncompressed.py /usr/src/linux-3.16.9999-raspberrypi/arch/arm/boot/Image /mnt/gentooboot/kernel.img

Config preparations

The next steps should be self-explanatory and may be adjusted according the current context.
Portage - Compiler settings - /mnt/gentoo/etc/portage/make.conf
        
        CFLAGS="-O2 -pipe -march=armv6j -mfpu=vfp -mfloat-abi=hard"
        CXXFLAGS="${CFLAGS}"
        LINGUAS="de"
        CHOST="armv6j-hardfloat-linux-gnueabi"
        USE="bindist"
        PORTDIR="/usr/portage"
        DISTDIR="${PORTDIR}/distfiles"
        PKGDIR="${PORTDIR}/packages"
        GENTOO_MIRRORS="http://ftp.halifax.rwth-aachen.de/gentoo/"
        SYNC="rsync://rsync16.de.gentoo.org/gentoo-portage"
        FEATURES="${FEATURES} parallel-fetch"
        EMERGE_DEFAULT_OPTS="--with-bdeps=y"
Timezone
        
        cp /mnt/gentoo/usr/share/zoneinfo/Europe/Berlin /mnt/gentoo/etc/localtime
        echo "Europe/Berlin" > /mnt/gentoo/etc/timezone
SD card setup - /mnt/gentoo/etc/fstab
        
        # /dev/mmcblk0p1
        UUID=1F3C-0E60                                  /boot        auto        noauto,noatime    1 2
        # /dev/mmcblk0p3
        UUID=00db1598-09ed-49a0-bd5d-0a3f92142dcf       /            ext4        noatime           0 1
        # /dev/mmcblk0p2
        UUID=3314c1f0-a9a2-4368-9dc6-abd604cef99c       none         swap        sw                0 0
Kernel Parameters
        touch /mnt/gentooboot/cmdline.txt
        echo "dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p3 rootfstype=ext4 elevator=deadline rootwait" > /mnt/gentooboot/cmdline.txt
Copy needed firmware
        
        git clone --depth 1 git://github.com/raspberrypi/firmware/
        cp firmware/boot/* /mnt/gentooboot
        cp -r firmware/modules /mnt/gentoo/lib/

Enter via chroot

        
        cp /usr/bin/qemu-arm /mnt/gentoo/usr/bin
        mount -o bind /dev /mnt/gentoo/dev && mount -t sysfs none /mnt/gentoo/sys && mount -t proc none /mnt/gentoo/proc
        chroot /mnt/gentoo /usr/bin/qemu-arm /bin/bash
        uname -ra # to check new environment
        source /etc/profile
        update-env
        passwd
General config
        
        ln -s /etc/init.d/net.lo /etc/init.d/net.eth0
        rc-update add net.eth0 boot
        # rc-update del hwclock boot && rc-update add swclock boot -> was not needed for me as already set
        rc-update add sshd default
        eselect profile list # if change needed, my setting was already correct
Exit chroot
        
        exit
        umount /mnt/gentoo/dev && umount /mnt/gentoo/proc && umount /mnt/gentoo/sys && umount /mnt/gentoo/
        umount /mnt/gentooboot
After moving the SD card to the Raspi it it easy to connect via SSH.

SSH Connect

My LAN adapter is configured to 192.168.3.1 so I had to search the Raspi there:
    
        nmap 192.168.3.0/24 # to find IP of the raspi
        ssh root@192.168.3.13

Post-Config

Configure clock
The Raspi has no hardware clock to NTP seams to be the choice for synchronisation:
    
        emerge ntp && rc-update add ntp-client default
Force GPU to minimun RAM
        
        mount /boot/
        nano /boot/config.txt
    ->
        gpu_mem=16
        arm_freq=900
        core_freq=333    
        sdram_freq=450
        over_voltage=2
        force_turbo=1
Hostnanme
By default the hostname is "localhost", but it should be set to unique name in /etc/conf.d/hostname
Locales
I switched my locale to have German based keyboards and behaviour:
/etc/env.d/02locale
        
        LANG="de_DE.UTF-8"
        LC_COLLATE="C"
        LC_CTYPE="de_DE.UTF-8"
        LC_NUMERIC="de_DE.UTF-8"
        LC_TIME="de_DE.UTF-8"
        LC_MONETARY="de_DE.UTF-8"
        LC_MESSAGES="en_US.UTF-8"
        LC_PAPER="de_DE.UTF-8"
        LC_NAME="de_DE.UTF-8"
        LC_ADDRESS="de_DE.UTF-8"
        LC_TELEPHONE="de_DE.UTF-8"
        LC_MEASUREMENT="de_DE.UTF-8"
        LC_IDENTIFICATION="de_DE.UTF-8"
        LANGUAGE="de_DE:de:en_US:en"
        COUNTRY=DE
        GDM_LANG="de_DE.utf8"
        LC_ALL="de_DE.utf8"
/etc/locale.gen
        
        en_US.UTF-8 UTF-8
        de_DE.UTF-8 UTF-8
        env-update && source /etc/profile
Common Tools
To have a nice known environment I installed common used tools and also used the opportunity to clean the system a bit:
    
        emerge eix
        eix-remote update && eix-sync && emerge -uDNa @world && emerge --depclean -a && revdep-rebuild -p
        emerge links htop portpeek usbutils pciutils gentoolkit genlop perl-cleaner raspberrypi-userland wireless-tools wpa_supplicant
        portpeek -arq
        eix-test-obsolete
        eclean -pd distfiles && perl-cleaner --reallyall -p

WIFI

For flexibility I connected a little tiny wireless LAN device, Edimax EW-7811Un (7392:7811). To find the correct driver and module I used "dmesg":
    dmesg | grep -C 3 WLAN
        [3.189968] usb 1-1.2: new high-speed USB device number 4 using dwc_otg
        [3.311697] usb 1-1.2: New USB device found, idVendor=7392, idProduct=7811
        [3.329911] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
        [3.338946] usb 1-1.2: Product: 802.11n WLAN Adapter
        [3.359819] usb 1-1.2: Manufacturer: Realtek
        [3.365804] usb 1-1.2: SerialNumber: 00e04c000001
        [5.095714] usb 1-1.2: USB disconnect, device number 4
After some googling I found the needed module, named RTL8192cu. So I added the "8192cu" to "/etc/conf.d/modules" for autoloading it. By some testing with wpa_supplicant with the nl80211 driver (as I expected to be compatible with my 8192 device). After: 
    
        wpa_supplicant -Dnl80211 -iwlan0 -C/var/run/wpa_supplicant/ -c/etc/wpa_supplicant/wpa_supplicant.conf -dd
I received: 
    
        rtl8192 Could not open file /sys/class/net/wlan0/phy80211/name
Then I tried the default driver, which worked nicely: 
    
        wpa_supplicant -iwlan0 -C/var/run/wpa_supplicant/ -c/etc/wpa_supplicant/wpa_supplicant.conf -dd
At the end I was able to symlink in init.d to have autostart:
    
        ln -s /etc/init.d/net.lo /etc/init.d/net.wlan0
        rc-update add net.wlan0 boot

References

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