7月 17, 2017

Raspberry Pi : Linux

System Architecture

The Raspberry Pi is an ARM-based device and therefore needs binaries compiled for this architecture.

ARMv6 (BCM2835): Raspberry Pi Model A, A+, B, B+, Zero, Zero W

Architecture: ARMv6
Processor: Broadcom BCM2835 700MHz
RAM: 512MB
SD:Full SD
USB:2
Ethernet:10/100

ARMv7 (BCM2836): Raspberry Pi 2 (based on Model B+)

Architecture: ARMv7 Cortex-A7
Processor: Broadcom BCM2836 900MHz
RAM: 1GB
SD: Micro SD
USB: 4
Ethernet: 10/100

ARMv8 (BCM2837): Raspberry Pi 3

Architecture: ARMv8 Cortex-A53
Processor: Broadcom BCM2837 1.2GHz
RAM: 1GB
SD: Micro SD
USB: 4
Ethernet: 10/100
Wireless: B/G/N, Bluetooth

Linux Kernel

The Raspberry Pi kernel is stored in GitHub and can be viewed at github.com/raspberrypi/linux

Updating your kernel

If you use the standard Raspbian update/upgrade process,


sudo apt update
sudo apt full-upgrade

this will automatically update the kernel to the latest stable version.

Building a new kernel

Local building

install Git and the build dependencies


sudo apt install git bc bison flex libssl-dev make
sudo apt install libssl-dev

get the sources


git clone --depth=1 https://github.com/raspberrypi/linux

--depth=1

Kernel configuration

Raspberry Pi 1, Pi Zero, Pi Zero W, and Compute Module


cd linux
KERNEL=kernel
make bcmrpi_defconfig

Raspberry Pi 2, Pi 3, Pi 3+, and Compute Module 3


cd linux
KERNEL=kernel7
make bcm2709_defconfig

Raspberry Pi 4


cd linux
KERNEL=kernel7l
make bcm2711_defconfig

Customising the Kernel version


CONFIG_LOCALVERSION="-v7l-MY_CUSTOM_KERNEL"

Building then installing


make -j4 zImage modules dtbs
sudo make modules_install
sudo cp arch/arm/boot/dts/*.dtb /boot/
sudo cp arch/arm/boot/dts/overlays/*.dtb* /boot/overlays/
sudo cp arch/arm/boot/dts/overlays/README /boot/overlays/
sudo cp arch/arm/boot/zImage /boot/$KERNEL.img

Cross-compiling

Install toolchain


git clone https://github.com/raspberrypi/tools ~/tools
echo PATH=\$PATH:~/tools/arm-bcm2708/arm-linux-gnueabihf/bin >> ~/.bashrc
source ~/.bashrc


sudo apt install zlib1g-dev:amd64

Get sources


git clone --depth=1 https://github.com/raspberrypi/linux

Install cross-compiling tools


sudo apt install git bc bison flex libssl-dev make libc6-dev libncurses5-dev

Build

Pi 1, Pi Zero, Pi Zero W, or Compute Module


cd linux
KERNEL=kernel
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- bcmrpi_defconfig

Pi 2, Pi 3, Pi 3+, or Compute Module 3


cd linux
KERNEL=kernel7
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- bcm2709_defconfig

Pi 4


cd linux
KERNEL=kernel7l
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- bcm2711_defconfig


make -j4 ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- zImage modules dtbs

Install directly onto the SD card

mount partitions


mkdir mnt
mkdir mnt/fat32
mkdir mnt/ext4

sudo mount /dev/sdb6 mnt/fat32
sudo mount /dev/sdb7 mnt/ext4

install the modules


sudo env PATH=$PATH make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- INSTALL_MOD_PATH=mnt/ext4 modules_install

copy the kernel and Device Tree blobs


sudo cp mnt/fat32/$KERNEL.img mnt/fat32/$KERNEL-backup.img
sudo cp arch/arm/boot/zImage mnt/fat32/$KERNEL.img
sudo cp arch/arm/boot/dts/*.dtb mnt/fat32/
sudo cp arch/arm/boot/dts/overlays/*.dtb* mnt/fat32/overlays/
sudo cp arch/arm/boot/dts/overlays/README mnt/fat32/overlays/
sudo umount mnt/fat32
sudo umount mnt/ext4

Another option is to copy the kernel into the same place, but with a different filename, you can then edit the config.txt file to select the kernel that the Pi will boot into:


kernel=kernel-myconfig.img

Getting the kernel headers

These provide the various function and structure definitions required when compiling code that interfaces with the kernel.


sudo apt install raspberrypi-kernel-headers

Installing Linux Distribution for Raspberry Pi

Installing Arch Linux ARM

Raspberry Pi 2

Start fdisk to partition the SD card:


  fdisk /dev/sdX

At the fdisk prompt, delete old partitions and create a new one:

Type o. This will clear out any partitions on the drive.
Type p to list partitions. There should be no partitions left.
Type n, then p for primary, 1 for the first partition on the drive, press ENTER to accept the default first sector, then type +100M for the last sector.
Type t, then c to set the first partition to type W95 FAT32 (LBA).
Type n, then p for primary, 2 for the second partition on the drive, and then press ENTER twice to accept the default first and last sector.
Write the partition table and exit by typing w.

Create and mount the FAT filesystem:


  mkfs.vfat /dev/sdX1 mkdir boot mount /dev/sdX1 boot

Create and mount the ext4 filesystem:


  mkfs.ext4 
  /dev/sdX2 
  mkdir root 
  mount /dev/sdX2 root

Download and extract the root filesystem (as root, not via sudo):


  wget http://os.archlinuxarm.org/os/ArchLinuxARM-rpi-2-latest.tar.gz 
  bsdtar -xpf ArchLinuxARM-rpi-2-latest.tar.gz -C root 
  sync

Move boot files to the first partition:


  mv root/boot/* boot

Unmount the two partitions:


  umount boot root

Insert the SD card into the Raspberry Pi, connect ethernet, and apply 5V power.
Use the serial console or SSH to the IP address given to the board by your router.

Login as the default user alarm with the password alarm.
The default root password is root.

DEBIAN + PIXEL: RASPBERRY PI OS FOR MAC AND PC

The Raspberry Pi Foundation announced a new operating system for Mac and PC computers. It’s called Debian + PIXEL.

The new software enables you to install a Raspberry Pi-like OS on your computer. It boots from a DVD, USB Thumb drive or inside a virtual environment.

With Debian + PIXEL you carry on using your regular operating system. But can boot into the coding environment when you want to experiment with coding, Linux or software development.

The OS has most of the software that comes with Raspbian. Like the Raspberry Pi, it’s ideal for makers and coders.

Only now, you don’t even need to buy Raspberry Pi hardware to discover the learning environment. It’s also going to make life easier for code clubs and teachers.

It’s a “live” distribution so can be run from a DVD or USB stick without needing to change your current OS. This is great for using the environment without the headache of dual booting or dedicating the device to PIXEL permanently.

Download Image

Click here to download a copy of Debian + PIXEL

The image is a standard ISO file so can be written to a DVD or USB drive using your favourite utility.

Burn Image

Etcher

To write SD/USB images I use Etcher using this guide : Write SD Card Images Using Etcher On Windows, Linux & Mac.

Etcher can be downloaded from http://www.etcher.io/ and is available for Windows, Linux and Mac.

You browse to the image file and select a drive. The list of drives provides a nice set of information so it should be clearer exactly what physical device you are selecting.

When selecting image files you can select IMG and ISO files as expected but also Zip files. This allows you to burn Raspberry Pi images without even extracting them from the source Zip files.

Depending on the state of the SD card you are using you may need to format it first. On Windows I always use the official SD Formatter application.

Rawrite32

The Rawrite32 application has a simple interface.
Make sure that you have inserted a blank USB drive into your computer.
Click the "open" button and navigate to the downloads folder and find the Fedora image that you downloaded earlier on.
Click on the target dropdown list and choose the drive letter for your USB drive.

Boot

The exact process to boot the image will depend on your hardware.
You need modify the Bios settings to allow the system to boot from a USB drive.
If your machine has a standard BIOS (i.e. not UEFI, although technically speaking UEFI is becoming more standard) then all you need to do to boot into a live version of Fedora is to reboot your computer with the USB drive still plugged in.

Virtual Machines

It is also possible to run this ISO image as a Virtual Machine.
I can load this iso image within Oracle’s VirtualBox on my MacbookAir .

Unfortunately any changes you make or save will be lost when you next reboot, so next we need to setup persistence to allow us to configure the operating system and save any files.

My workaround is to overlap possible changed folders:

Create disk partitions


Device     Boot    Start      End  Sectors  Size Id Type
/dev/sda1           2048    22527    20480   10M 83 Linux
/dev/sda2          22528   227327   204800  100M 83 Linux
/dev/sda3         227328   432127   204800  100M 83 Linux
/dev/sda4         432128 50331647 49899520 23.8G  5 Extended
/dev/sda5         434176 17211391 16777216    8G 83 Linux
/dev/sda6       17213440 48670719 31457280   15G 83 Linux
/dev/sda7       48672768 49287167   614400  300M 83 Linux
/dev/sda8       49289216 50331647  1042432  509M 83 Linux

Copy installed files to the following partitions


/dev/sda1           8887    3038      5133  38% /etc
/dev/sda2          95054   10571     77315  13% /sbin
/dev/sda3          95054   11821     76065  14% /bin
/dev/sda5        8125880 4666924   3023144  61% /usr
/dev/sda7         289293   99204    170633  37% /opt
/dev/sda8         496548   74144    392248  16% /home

Mount the copied partitions after "Debian + PIXEL" is booted

Adding Persistence

As the virtual machine boots from a DVD image it is unable to save any changes to the disk. To overcome this limitation we can use virtual hard disk drive that we created earlier which will be used to save any data or changes to the operating system. These files will then be made available when the virtual machine starts.

During the setup you will have created the virtual hard disk, but the disk will need preparing and formatting before it can be used. First create a disk partition using cfdisk. Start a terminal and after checking you are on the correct system (the prompt will say pi@raspberrypi) enter:


sudo cfdisk /dev/sda

Accept the first option of using the disk as a gpt disk. Now check the details are as expected - in particular that it does not show any partitions that are in use and that it matches the size of the disk created previously.

Choose "New" to create a new partition, accept the default of using the full disk drive as a single partition.

As you can see the file system type has defaulted to Linux, so use the right arrow to select "Write". Type yes to write the changes and then choose Quit.

The new partition is called sda1. It can now be formatted with the ext4 file system which is commonly used by Linux. This is done by running:


sudo mkfs.ext4 /dev/sda1

Now give the disk the name "persistence" using the elabel command.


sudo e2label /dev/sda1 persistence

You will now need to add a persistence.conf file to the disk. Enter the following commands to mount the disk on a temporary mount point:


sudo mkdir /mnt/temp

sudo mount /dev/sda1 /mnt/temp

Add the file using:


sudo leafpad /mnt/temp/persistence.conf

Add the following on the top line:


/ union

Also create a blank second line (as I found that it did not work without it). Save the file and quit from the editor.

Now reboot the virtual machine and persistence will be enabled.

Run Raspberry Pi Desktop on a virtual machine

Raspberry Pi Desktop

Debian with Raspberry Pi Desktop is the Foundation’s operating system for PC and Mac. You can create a live disc, run it in a virtual machine, or even install it on your computer.

Download "Debian Buster with Raspberry Pi Desktop"

Run Raspberry Pi on VirtualBox

Create the virtual machine

Install

This will help you to install the system on the created Virtual Box drive.

Run with persistent storage

After run with persistent storage, the storage and partitions are:

Unfortunately any changes you make or save will be lost when you next reboot, so we need to setup persistence to allow us to configure the operating system and save any files.

We need to create partitions to replace the folders which may be changed after the software installation or executions:


bin  /dev/sda1  100M
etc  /dev/sda2  100M
sbin /dev/sda5  1G
opt  /dev/sda6  1G
usr  /dev/sda7  8G
home /dev/sda9  5.6G

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