Build system

Description

The OLPC XO software build system has the requirement of combining software from various sources:

• A specific set of packages from Fedora Linux
• Some OLPC-specific packages which are not available in Fedora
• Some OLPC-forked packages where the versions in Fedora do not suit our needs exactly
• Sugar activities
• OLPC-specific configuration

The build system outputs software images which can be flashed to XOs for testing and deployment.

While OLPC produces generic software images, almost all deployments will want to add some level of customization (specific Sugar activities and software applications, default settings, etc). To allow for this, the build system can be easily installed and used by deployments and developers, allowing for easy local customisation.

Current build system

OS Builder is used for current and upcoming OLPC software releases. Compared to its predecessors, it makes extensive use of Fedora's build tools under a higher layer which allows for organisation of components and easy customization. It is also easier to install and use.

Files produced by the build system

The build system produces sets of files for each targeted OLPC model, some starting with the build's number such as os883. It also produces a representation of the resulting filesystem for the OLPC model as one or more large files, that the OLPC's firmware knows how to copy to its built-in flash memory. The Release notes for a build document this update procedure. The filename extensions include:

activities.txt, libraries.txt

the Activities and Collections incorporated into the build. It is used for build to build regression testing.

.files.txt.gz

a list of the entries in the filesystem. Click to view. Most web browsers can view this compressed file directly. Used for build to build regression testing.

.img and .crc

a non-partitioned JFFS2 file system image for an XO-1. The XO-1's firmware knows how to copy this to NAND Flash memory.

file.md5

a cryptographic hash of the contents of the file file, so that a download can be verified.

.onu

a file of checksums for the .uim UBIFS file system images for the XO-1, used by its firmware.

packages.txt

the Fedora or OLPC RPM packages that went into the build. Used for build to build regression testing.

.toc and .usb

Information for performing a system update using olpc-update without requiring network access, see also .usb

.tree.tar.lzma

the filesystem, in LZMA compressed tar format. If you carefully unpack this onto a Linux partition on a USB drive or SD card and make some changes, you may be able to boot an XO from it.

.uim

a representation of the blocks of a UBIFS file system images for the XO-1. Its firmware's knows how to copy this to its built-in NAND flash memory, see also .onu.

.zd2 , .zd4, .zd8

zhashfs compressed disk images containing a boot and root filesystem, for XOs with eMMC, microSD, or SD card internal storage, such as XO-1.5 and XO-1.75. The firmware knows how to copy this to internal storage. The number indicates the size of the image in GB.

Earlier files

.ext3.img

raw disk image including partition table, suitable for copying onto a USB drive, see OS images for USB disks.

Historical build systems and their evolution

Pilgrim was the first build system, developed by OLPC and Red Hat, and used for OLPC's early software releases.

Puritan was developed after pilgrim started to show signs of outgrowing its design, calling for a cleaner and leaner system. However, it was never adopted officially by OLPC.

Image builder was developed as a post-processing tool to complement Pilgrim when OLPC decided to hand off part of the image customization process to deployments; it takes Pilgrim images and applies various customizations to them to produce a new output image. This started to outgrow its design when various parts of pilgrim needed to be copied into Image builder in order to be able to make more invasive customizations.

For initial software development for the XO-1.5 laptop, a desire to move to standard Fedora build tools emerged. fedora-xo was used to produce the first XO-1.5 software release, but the resultant build system was messy and left no systematic process for customizations by deployments. This lead to design goals for future build systems to balance use of Fedora build tools, organisation of OLPC's special requirements, and the ability for deployments to easily obtain and use the tool while making customizations to the image.

School Server Build Tools

See XS Building Software for details.