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Bakery

Use a Pi to make a Pi

Objective

Use the Raspberry Pi to write images to other SD cards. The primary objective is to be able create new Raspberry Pi OS cards but it can obviously be used for copying any images.

WARNING 1

This software is designed to wipe and write to any SD card that you connect via the USB connectors on a Raspberry Pi. There is obviously a real danger of data loss if used without care.

WARNING 2

Did you read WARNING 1? If not, go back and read it again.

Requirements

Hardware

  • PiFace Control and Display
  • USB to SD adapter

Software

  • python3-pifacecad
  • python3-pyudev

The pifacecommon library from python3-pifacecad must be version 4.1.1 or later. At time of writing, the version that is in the Raspbian respositories is 4.0 so the 'testing' branch from Github should be used. Alternatively, the interrupts.py file may be replaced, as described below.

Set up

A Debian Squeeze based distribution must be used as the PiFace libraries are not currently available for others. Raspbian may be used but Moebius is recommended to maximise the available disk space for images. Moebius may be downloaded from here:

Upgrade:

apt-get update
apt-get upgrade
apt-get clean all

The last line cleans up the apt cache because there is not a lot of free space in the root partition.

Install the required packages:

apt-get install python3-pifacecad python3-pyudev
apt-get clean all

Enable SPI by removing this line from /etc/modprobe.d/raspi-blacklist.conf:

blacklist spi-bcm2708

It is recommended that you do not expand the root filesystem but instead create a separate partition for the storage of images.

Reboot to enable the SPI module and PiFace CAD.

Extract Bakery into:

/home/pi/Bakery

Important: Until a version of the PiFace libraries newer than 4.0.0 becomes available you must patch the PiFace interrupts.py file:

cp /home/pi/Bakery/pifacecommon/interrupts.py /usr/lib/python3/dist-packages/pifacecommon/interrupts.py

Either start Bakery manually, as shown in the 'Operation' section below, or set it to start on boot by copying the file:

/home/pi/Bakery/init.d/bakery

to /etc/init.d, making sure that it is executable, and running:

sudo update-rc.d bakery defaults

Configuration

Bakery looks for a configuration file called bakery.cfg either in the current directory or in /etc. This should contain:

[images]
source=/path/to/images/directory

The images inside this directory should be contained inside a subdirectory together with any script to be executed after writing, for example:

Raspbian/rbian-140107.img.gz
Bakery/bakery.img.gz
Bakery/bakery.vars
Bakery/bakery.post.1
  • bakery.img.gz is a minimal image configured to run Bakery
  • bakery.vars is a list of options to collect, which are then passed as environment variables to the post install scripts
  • bakery.post.1 is a script that copies some images into the correct location for it to use

The opts file comprises line in the format:

VARIABLE=<default value>

and these will be passed to all post install scripts.

Operation

Run with:

sudo python3 bakery.py

Images are found in /home/pi/images and should be gzipped.

Controls

Button Main view Load image view Delete image view System status view
1 Switch between lines No action
2 Next view
3 No action
4 Scroll display
5 Write image (hold for 5 seconds) Scan selected device Delete image (hold for 5 seconds) Execute displayed action (hold for 5 seconds)
Rocker press Display further information No action
Rocker Select image or device Select device to scan Select image to delete Show next data or option

On the 'Load image view', after a device has been scanned, any images found can be selectively copied into the Bakery image store with buttons 2 (yes) and 3 (no).

System information

The system information view will display:

  • IP address
  • CPU temperature
  • Total image storage space
  • Used image storage space
  • Free image storage space

There are options to reboot or shutdown.

Images

Images should be stored in subdirectories of the source directory defined in the configuration file (see above) and they should be zipped up using:

gzip image.img

so that the file has a .img.gz extension.

Note that images provided by distributions may be packaged up in various forms, such as tar, tar.gz and zip. None of these will work so you will need to unpack them and gzip the image.

Configuration scripts

The configuration scripts for an image must be in the same directory as the image and named consistently. For image.img the scripts must be called:

image.post.1
image.post.2
image.post.3
(etc)

The number indicates the order in which they are executed.

The scripts are passed environment variable defined in the image.var plus:

Variable Description
$DEVICE Device path. Eg, /dev/sda
$PARTITION1 Device path of the first partition. Eg, /dev/sda1
$PARTITION2 Device path of the second partition. Eg, /dev/sda2
(etc)
$IMGDIR The directory containing the image and other related files

The title of the script is the first comment in the format:

#TITLE# Config script

The text 'Config script' will be displayed during its execution.

Example script

#!/bin/bash
#TITLE# Set the hostname
# The root partition is the second partition on the disk

mount $PARTITION2 /mnt
echo new-hostname > /mnt/etc/hostname
umount $PARTITION2

Longer term plans

The SD card writer (and duplicator) is just the first step towards a 'control centre' device that can be used for managing a network of Raspberry Pis in a classroom environment. Future features could include:

  • Install a very small 'seed' image that then completes installation over the network. For a large number of installs this may be quicker.
  • Store known configurations for a quick refresh for a particular user
  • DHCP server
  • Network router/gateway
  • FTP, NFS, Samba
  • Git - Gitlab and proxy to Github
  • Update services - eg, apt and yum server
  • Copy files to and from Pis on the network. In particular, copy files onto all Pis.