Einführung in die Portierung¶
Dieser erste Abschnitt wird Sie in die Besonderheiten der Portierung von Ubuntu Touch auf ein Android-Gerät einführen. Beachten Sie, dass er für die allgemeine Öffentlichkeit geschrieben ist, nicht primär für den erfahrenen Portierungsentwickler. In den folgenden Abschnitten haben wir uns um eine Differenzierung bemüht, indem wir den Haupttext knapper gehalten haben, um den Bedürfnissen des erfahreneren Lesers gerecht zu werden, während wir Links zu ergänzender Lektüre für den weniger erfahrenen Leser bereitstellen.
Der Leitfaden als Ganzes ist als eine Abfolge von Schritten geschrieben, die beschreiben, wie eine ideale Portierung ablaufen könnte. Eine Portierung ist jedoch unvorhersehbar und chaotisch. Jedes Gerät ist anders und in der Realität werden Sie wahrscheinlich einige Schritte wiederholen und überarbeiten, andere Schritte überspringen und neue und undokumentierte Herausforderungen entdecken.
Was ist Ubuntu Touch?¶
Ubuntu Touch ist ein Open-Source-Betriebssystem für mobile Geräte. Es kann auf Geräte portiert werden, die ursprünglich mit Android OS ausgeliefert wurden. Leider sind die meisten dieser Geräte bis zu einem gewissen Grad auf proprietäre Software angewiesen.
To be specific, device vendors tend to keep the code that speaks directly to the device hardware (the low level device drivers) proprietary. These components are commonly called the vendor ‚blobs‘ (Binary Large OBjects). The vendor blobs need to be incorporated into an Ubuntu Touch port. Note that these components are specific not only to each device, but also to each Android version. It is therefore necessary to secure the correct version of these components when building a port.
Aus diesem Grund kann Ubuntu Touch für die meisten kommerziellen Geräte nicht komplett aus dem Quellcode gebaut werden. Stattdessen beinhaltet die Portierung des Systems auf diese Geräte die Integration der zuvor erwähnten Vendor Blobs in den Rest des Systems, der aus dem Quellcode gebaut werden kann.
The next component of Ubuntu Touch is a pre-compiled root filesystem which needs to be installed on the device. This component does not communicate directly with the device hardware. Instead, this communication is mediated by a Hardware Abstraction Layer (HAL) which needs to be built for each specific device, because each device has its specific hardware architecture. This component is called Halium and is available in different versions corresponding to different Android versions.
The Halium project enables Linux systems to run on Android hardware. It is a joint effort by multiple mobile operating systems, notably Lune OS, Droidian and Ubuntu Touch.
Ubuntu Touch porting builds on top of the Halium GSI. The Halium GSI is discussed further below. At times it may also be helpful to test with one of the other operating systems to debug a problem from different angles.
Halium is an indispensible part of an Ubuntu Touch port and is available in the form of open source software. Developing a new version of Halium is a very considerable task which is why only a few versions of Halium are available. Each port of Ubuntu Touch has to be based on one of the available Halium versions and vendor blobs from the corresponding Android version. See the first two columns of the table below for details.
- Ein Ubuntu Touch-Port setzt sich also aus diesen Komponenten zusammen:
Das Ubuntu Touch (UT) Root-Dateisystem (rootfs)
Halium (enthalten in den Boot- und System-Images)
Die Vendor Blobs
You, the porter, need to build a Halium kernel, which is installed together with the Ubuntu Touch rootfs and the Halium GSI, to create a functioning Ubuntu Touch port.
Android and Halium versions¶
Halium is built using source code for a modified version of the Android operating system called LineageOS (see the LineageOS website and wiki). The required source code is available online and needs to be downloaded and configured to build the correct Halium version for each individual device port. The table below shows which versions are required for the different Halium versions.
Android-Version |
Halium-Version |
Lineage OS (LOS) |
|---|---|---|
7.1 |
7.1 |
14.1 |
9.0 |
9.0 |
16.0 |
10.0 |
10.0 |
17.1 |
11.0 |
11.0 |
18.1 |
12.0 |
12.0 |
19.1 |
13.0 |
13.0 |
20.0 |
Since 20.04, Ubuntu Touch ports are normally based on Halium 9.0 or later. Older versions of Halium are considered deprecated and are no longer supported for new ports.
Generic System Image¶
Starting with Android version 9.0, a significant change of architecture was introduced. The device-specific vendor blobs now reside on a separate partition instead of sharing a partition with the rest of the system image. This separation of device-specific code from generic code made possible what is known as the Generic System Image (GSI).
A GSI is a system image that is built to be able to function with a wide range of devices. Android devices, as of version 9.0, use a GSI. For more information, see the Android Developer pages
The development of the Android GSI architecture also cleared the way for the now available generic Halium 9.0 arm64 system image (hereafter referred to as the Halium GSI, or simply the GSI) which is used for Ubuntu Touch. This, however, is somewhat different from the Android GSI. For a more detailed explanation of the Halium GSI, please refer to the wiki page on Gitlab CI builds of the generic Halium system image.
What does this mean for the porting process?¶
Since the GSI is a prebuilt, device-independent component, it effectively simplifies the task of building a viable port by removing much of the meticulous and time consuming task of getting the hardware-specific vendor blobs compiled into the system image and configured to function properly.
Die Herausforderungen des Portierungsprozesses¶
Building the necessary components and getting them to work together properly always involves an amount of code modifications, configuring and testing.
Luckily, there is a community of porters out there who are eager to see Ubuntu Touch ported to new devices. When you run into trouble, you should search the sources below (Hilfe der Community erhalten) to see if others before you have solved the issue. There are online Telegram chat groups you can join to ask for help, but please bear in mind that those participating are doing so in their spare time.
Bemerkung
In the past there used to be different methods for porting. Find the historic details linked in the deprecated porting section.
Vorkenntnisse und Fähigkeiten¶
Porters come in all sizes and shapes, so to speak. Therefore, this guide does not presuppose extensive knowledge or skills in any particular field. You should, however, as a bare minimum be familiar with some common shell commands and be comfortable working from the terminal on you host PC. Furthermore, the guide is based on a host PC running Linux. If you have some knowledge of programming, this will come in handy at some point, especially if you are familiar with C / C++. Also, you should familiarize yourself with git and set up a Github or Gitlab account to keep track of your code changes. It is wise to start documenting your steps from the very beginning.
We have attempted to give a certain amount of explanation along the way. However, this guide is not an in-depth reference into the architecture and inner workings of Ubuntu Touch, and gaining a deeper understanding will consequently require an amount of research on your part.
Hilfe der Community erhalten¶
Wenn Sie auf Schwierigkeiten stoßen, und das werden Sie, beziehen Sie sich auf eine oder mehrere der unten aufgeführten Quellen:
Allgemeiner Hinweis¶
The more rigorous you are at making notes and documenting your steps, the less time you will spend backtracking your steps and guessing your way along. When dealing with issues that arise along the way, it is wise to work on them one at a time. If you try to correct several things at once, you risk ending up trying to guess which changes solved a given issue, which easily leads to breaking the functionality in question once more at some later stage.
If you are not discouraged after reading this, we welcome your efforts and wish you the best of luck!
The next section presents a key to the rest of this guide.