Update README with some information on how the build works (#136)

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Ben Pirt 2017-12-15 11:31:40 +00:00 committed by XECDesign
parent add380ed55
commit c677ef8763

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@ -3,13 +3,13 @@
_Tool used to create the raspberrypi.org Raspbian images_
### TODO
1. Documentation
## Dependencies
On Debian-based systems:
pi-gen runs on Debian based operating systems. Currently it is only supported on
either Debian Stretch or Ubuntu Xenial and is known to have issues building on
earlier releases of these systems.
To install the required dependencies for pi-gen you should run:
```bash
apt-get install quilt parted realpath qemu-user-static debootstrap zerofree pxz zip \
@ -80,6 +80,48 @@ IMG_NAME='Raspbian'
```
## How the build process works
The following process is followed to build images:
* Loop through all of the stage directories in alphanumeric order
* Move on to the next directory if this stage directory contains a file called
"SKIP"
* Run the script ```prerun.sh``` which is generally just used to copy the build
directory between stages.
* In each stage directory loop through each subdirectory and then run each of the
install scripts it contains, again in alphanumeric order. These need to be named
with a two digit padded number at the beginning.
There are a number of different files and directories which can be used to
control different parts of the build process:
- **00-run.sh** - A unix shell script. Needs to be made executable for it to run
- **00-run-chroot.sh** - A unix shell script which will be run in the chroot
of the image build directory. Needs to be made executable for it to run.
- **00-debconf** - Contents of this file are passed to debconf-set-selections
to configure things like locale, etc.
- **00-packages** - A list of packages to install. Can have more than one, space
separated, per line.
- **00-packages-nr** - As 00-packages, except these will be installed using
the ```--no-install-recommends -y``` parameters to apt-get
- **00-patches** - A directory containing patch files to be applied
* If the stage directory contains files called "EXPORT_NOOBS" or "EXPORT_IMAGE" then
add this stage to a list of images to generate
* Generate the images for any stages that have specified them
It is recommended to examine build.sh for finer details.
## Docker Build
```bash
@ -179,3 +221,21 @@ 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.
## Skipping stages to speed up development
If you're working on a specific stage the recommended development process is as
follows:
* Remove the EXPORT_IMAGE and EXPORT_NOOBS files until you're ready to actually
generate an image
* Add SKIP files to the stages you don't want to build. For example, if you're
basing your image on the lite image you would add these to stages 3, 4 and 5.
* Run build.sh to build all stages
* Add SKIP files to the earlier successfully built stages
* Modify the last stage
* Rebuild just the last stage using ```sudo CLEAN=1 ./build.sh```
* Once you're happy with the image you can add the EXPORT files back in and
export your image to test