torch-pi-gen/README.md

# pi-gen

_Tool used to create the raspberrypi.org Raspbian images_


### TODO
1. Documentation


## Dependencies

On Debian-based systems:

```bash
apt-get install quilt parted realpath qemu-user-static debootstrap zerofree pxz zip \
dosfstools bsdtar libcap2-bin grep rsync
```

The file `depends` contains a list of tools needed.  The format of this
package is `<tool>[:<debian-package>]`.


## Config

Upon execution, `build.sh` will source the file `config` in the current
working directory.  This bash shell fragment is intended to set needed
environment variables.

The following environment variables are supported:

 * `IMG_NAME` **required** (Default: unset)

   The name of the image to build with the current stage directories.  Setting
   `IMG_NAME=Raspbian` is logical for an unmodified RPi-Distro/pi-gen build,
   but you should use something else for a customized version.  Export files
   in stages may add suffixes to `IMG_NAME`.

 * `APT_PROXY` (Default: unset)

   If you require the use of an apt proxy, set it here.  This proxy setting
   will not be included in the image, making it safe to use an `apt-cacher` or
   similar package for development.

   If you have Docker installed, you can set up a local apt caching proxy to
   like speed up subsequent builds like this:

       docker-compose up -d
       echo 'APT_PROXY=http://172.17.0.1:3142' >> config

 * `BASE_DIR`  (Default: location of `build.sh`)

   **CAUTION**: Currently, changing this value will probably break build.sh

   Top-level directory for `pi-gen`.  Contains stage directories, build
   scripts, and by default both work and deployment directories.

 * `WORK_DIR`  (Default: `"$BASE_DIR/work"`)

   Directory in which `pi-gen` builds the target system.  This value can be
   changed if you have a suitably large, fast storage location for stages to
   be built and cached.  Note, `WORK_DIR` stores a complete copy of the target
   system for each build stage, amounting to tens of gigabytes in the case of
   Raspbian.

 * `DEPLOY_DIR`  (Default: `"$BASE_DIR/deploy"`)

   Output directory for target system images and NOOBS bundles.


A simple example for building Raspbian:

```bash
IMG_NAME='Raspbian'
```


## Docker Build

```bash
vi config         # Edit your config file. See above.
./build-docker.sh
```

If everything goes well, your finished image will be in the `deploy/` folder.
You can then remove the build container with `docker rm -v pigen_work`

If something breaks along the line, you can edit the corresponding scripts, and
continue:

```bash
CONTINUE=1 ./build-docker.sh
```

There is a possibility that even when running from a docker container, the
installation of `qemu-user-static` will silently fail when building the image
because `binfmt-support` _must be enabled on the underlying kernel_. An easy
fix is to ensure `binfmt-support` is installed on the host machine before
starting the `./build-docker.sh` script (or using your own docker build
solution).


## Stage Anatomy

### Raspbian Stage Overview

The build of Raspbian is divided up into several stages for logical clarity
and modularity.  This causes some initial complexity, but it simplifies
maintenance and allows for more easy customization.

 - **Stage 0** - bootstrap.  The primary purpose of this stage is to create a
   usable filesystem.  This is accomplished largely through the use of
   `debootstrap`, which creates a minimal filesystem suitable for use as a
   base.tgz on Debian systems.  This stage also configures apt settings and
   installs `raspberrypi-bootloader` which is missed by debootstrap.  The
   minimal core is installed but not configured, and the system will not quite
   boot yet.

 - **Stage 1** - truly minimal system.  This stage makes the system bootable by
   installing system files like `/etc/fstab`, configures the bootloader, makes
   the network operable, and installs packages like raspi-config.  At this
   stage the system should boot to a local console from which you have the
   means to perform basic tasks needed to configure and install the system.
   This is as minimal as a system can possibly get, and its arguably not
   really usable yet in a traditional sense yet.  Still, if you want minimal,
   this is minimal and the rest you could reasonably do yourself as sysadmin.

 - **Stage 2** - lite system.  This stage produces the Raspbian-Lite image.  It
   installs some optimized memory functions, sets timezone and charmap
   defaults, installs fake-hwclock and ntp, wifi and bluetooth support,
   dphys-swapfile, and other basics for managing the hardware.  It also
   creates necessary groups and gives the pi user access to sudo and the
   standard console hardware permission groups.

   There are a few tools that may not make a whole lot of sense here for
   development purposes on a minimal system such as basic Python and Lua
   packages as well as the `build-essential` package.  They are lumped right
   in with more essential packages presently, though they need not be with
   pi-gen.  These are understandable for Raspbian's target audience, but if
   you were looking for something between truly minimal and Raspbian-Lite,
   here's where you start trimming.

 - **Stage 3** - desktop system.  Here's where you get the full desktop system
   with X11 and LXDE, web browsers, git for development, Raspbian custom UI
   enhancements, etc.  This is a base desktop system, with some development
   tools installed.

 - **Stage 4** - Raspbian system meant to fit on a 4GB card.  More development
   tools, an email client, learning tools like Scratch, specialized packages
   like sonic-pi, system documentation, office productivity, etc.  This is the
   stage that installs all of the things that make Raspbian friendly to new
   users.

 - **Stage 5** - The official Raspbian Desktop image. Right now only adds
   Mathematica.

### Stage specification

If you wish to build up to a specified stage (such as building up to stage 2
for a lite system), place an empty file named `SKIP` in each of the `./stage`
directories you wish not to include.

Then remove the `EXPORT*` files from `./stage4` (if building up to stage 2) or
from `./stage2` (if building a minimal system).

```bash
# Example for building a lite system
echo "IMG_NAME='Raspbian'" > config
touch ./stage3/SKIP ./stage4/SKIP ./stage5/SKIP
rm stage4/EXPORT*
sudo ./build.sh  # or ./build-docker.sh
```

If you wish to build further configurations upon (for example) the lite
system, you can also delete the contents of `./stage3` and `./stage4` and
replace with your own contents in the same format.