ARMImageSelection
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| * '''Packages affected''': livecd-rootfs | * '''Packages affected''': livecd-rootfs, debian-cd |
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| This specification describes an informational discussion held at UDS Jaunty in Mountainview about the right selection for images for the armel architecture | This specification describes an informational discussion held at UDS Jaunty in Mountainview about the right selection on initial images for the armel architecture in ubuntu 9.04 == Release Note == Ubuntu supports the ARMv7 architecture with the following images ... |
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| As we develop new ideas for features in Ubuntu, it's important to be able to communicate them clearly. This serves the purpose of making it clear what the feature is about, and allowing people to evolve an implementation strategy for it. Publishing this content gives our community a chance to participate in the discussion and design of a feature, and increases the chance that community members will feel confident enough to start work on the implementation of the feature. A good specification also allows community members who were not physically present at meetings discussing a topic to participate in the implementation of the spec. Bottom line: the better your spec, the better the chances that your ideas will be clearly understood by the review team. |
With the armel architecture appearing in ubuntu it needs to be identified which selection of images should be built. ARM uses very specific boot methods for hardware that can vary from board to board, the currently vfat/syslinux or iso9660/isolinux image setup used for other architectures will not boot right away, ARM will need special treatment and we need to identify a bootloader process that works for the majority of the devices. It will also need to be identified if we want to use live images with ubiquity or go for a textbased install via debian-installer, which will also be influenced by the flavours to be built (ubuntu-desktop might suit better for live images, while ubuntu-server will require to be built with debian-installer support) |
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| * Bob is the maintainer for the boot process for Ubuntu. In the Dapper cycle, he would like to work on getting the boot time down to two seconds from boot manager to GDM screen. He creates an entry for the specification in Launchpad, proposes it for the UBZ sprint, and starts writing out a braindump of it in the Ubuntu wiki. Magnus, who is in charge of UBZ scheduling, thinks it sounds fishy but approves it to make sure that the change is discussed and documented properly. He marks it as priority Medium because he isn't sure Bob will have time free for implementing it during Dapper. | Jon bought a new freescale pegatron netbook that he got without OS for only $150, he wants to install ubuntu on it, downloads a live rootfs from cdimage.ubuntu.com, fires up the image-merger tool he installed on his ubuntu desktop at home in which he then selects the proper kernel for his netbook. The tool asks him to plug in a USB key to be used for installation and within minutes Jon has a bootable USB key to install ubuntu from a livesystem on his new netbook. |
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| * Pedro works on Malone, in Launchpad. Before UBZ, he remembers that the dependency handling in the bug tracker is really not optimal. He writes out a Summary and Rationale in a Launchpad wiki page, registers it as a specification in Launchpad, and suggests it for UBZ. Monica, Launchpad manageress, thinks that this is really not the time to be talking about it and rejects the application for UBZ. He then indicates it for the next conference, UBB, and marks its priority is Low. * Jason is an Ubuntu and Rosetta user. He has noticed that changes made to translations are making their way into language packs but not to the upstream versions, and adds a specification that describes a way for getting upstream to use language packs. Monica also has a plan for this but hadn't described it in a spec, so she adds it to the UBZ spec list, and adds Carlos, Rosetta maintainer, as drafter for it. == Scope == This specification covers feature specifications for Ubuntu and Launchpad. It is not meant as a more general specification format. |
Willy has a nokia n810. He wants to use an ubuntu installation on it. Willy downloads the ubuntu-alternate-arm.img from cdimage.ubuntu.com, writes this image to an SD card, boots his nokia device from it and installs ubuntu to the internal flash memory. During the installation Willy selects the n8x0 kernel flavour and after a reboot his tablet boots into ubuntu. |
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| A specification should be built with the following considerations: | The livefs.sh script from the livecd-rootfs package needs to grow a --skip-kernel option that suppresses the installation of kernel images in the squashed rootfs, so kernel-less rootfs images can be created. |
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| * The person implementing it may not be the person writing it. It should be clear enough for someone to be able to read it and have a clear path towards implementing it. If it doesn't, it needs more detail. | An offline tool will be created that merges a downloadable squashfs with a kernel package for a selectable target board and writes the merged image file to a target device. |
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| * That the use cases covered in the specification should be practical situations, not contrived issues. | The ubuntu build servers will create debian-installer based images for armel that include all binary kernels for the possible target boards. The necessary armel related bits and pieces apart from the kernels are already available from debian. |
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| * Limitations and issues discovered during the creation of a specification should be clearly pointed out so that they can be dealt with explicitly. | The following set of images was discussed at UDS to be built for jaunty: |
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| * If you don't know enough to be able to competently write a spec, you should either get help or research the problem further. Avoid spending time making up a solution: base yourself on your peers' opinions and prior work. | * live ubuntu-desktop (kernel-less) * d-i ubuntu-server |
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| * Specifications should be written in clear, concise and correct English. If you're not a native speaker, co-editing the spec with somebody who is might be a good idea. | Possible images, if we get community support and requests were discussed as well but are more likely to show up in a later cycle: |
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| Specific issues related to particular sections are described further below. | * live netbook-remix (needs GL support for the desktop launcher) * live kubuntu * live xubuntu |
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| === Summary === | Future possible images are: |
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| The summary should not attempt to say '''why''' the spec is being defined, just '''what''' is being specified. === Rationale === This should be the description of '''why''' this spec is being defined. === Scope and Use Cases === While not always required, but in many cases they bring much better clarity to the scope and scale of the specification than could be obtained by talking in abstract terms. ==== Use Cases ==== Use cases are positive statements which (loosely) conform to a pattern like * A person and their role * The objective they want to achieve * The steps they go through * The positive result Specifically, describing the current unsatisfactory state of affairs is not a use case; that belongs in the Rationale section. === Implementation Plan === This section is usually broken down into subsections, such as the packages being affected, data and system migration where necessary, user interface requirements and pictures (photographs of drawings on paper work well). |
* live MID * An extremely small image which would fit in flash and wouldn't require mass storage such as a SATA disk |
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| To implement a specification, the assignee should observe the use cases carefully, and follow the design specified. He should make note of places in which he has strayed from the design section, adding rationale describing why this happened. This is important so that next iterations of this specification (and new specifications that touch upon this subject) can use the specification as a reference. | Installation from disk or flash devices as well as netbooted installs will be supported by debian-installer, the -desktop flavour as a default will be made avilable through an alternate image, optionally the user can select other flavours than desktop in the expert mode of debian-installer in this image, where tasksel is available to install all other possible flavours of ubuntu. |
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| The implementation is very dependent on the type of feature to be implemented. Refer to the team leader for further suggestions and guidance on this topic. | With the livecd-rootfs changes in place the build servers will be able to roll kernel-less squashfs images that will be provided for download. An offline GTK based tool will be written to select a target kernel and create an actual livefs. The mentioned tool will write the image to a target device (USB or SD card) as a final step. |
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| The specification process requires experienced people to drive it. More documentation on the process should be produced. | There are different bootloaders that can be used on ARM based systems, most common are uboot and redboot (JTAG based devices are out of scope, these have to be installed vendor side), currently it is up to the user to configure the bootloader to boot from the installation device. A possible solution that doesnt yet go into the image build could be provided by ARMSoftbootLoader but this is beyond the scope of this spec and probably rather a task for the jaunty+1 development cycle. |
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| The drafting of a specification requires English skills and a very good understanding of the problem. It must also describe things to an extent that someone else could implement. This is a difficult set of conditions to ensure throughout all the specifications added. There is a lot of difficulty in gardening obsolete, unwanted and abandoned specifications in the Wiki. == BoF agenda and discussion == We'll have a first public session on this on the first Monday in UBZ. |
Launchpad Entry: selection-of-arm-images
Created: 2009-01-20
Contributors: OliverGrawert StevenKowalik
Packages affected: livecd-rootfs, debian-cd
Summary
This specification describes an informational discussion held at UDS Jaunty in Mountainview about the right selection on initial images for the armel architecture in ubuntu 9.04
Release Note
Ubuntu supports the ARMv7 architecture with the following images ...
Rationale
With the armel architecture appearing in ubuntu it needs to be identified which selection of images should be built. ARM uses very specific boot methods for hardware that can vary from board to board, the currently vfat/syslinux or iso9660/isolinux image setup used for other architectures will not boot right away, ARM will need special treatment and we need to identify a bootloader process that works for the majority of the devices. It will also need to be identified if we want to use live images with ubiquity or go for a textbased install via debian-installer, which will also be influenced by the flavours to be built (ubuntu-desktop might suit better for live images, while ubuntu-server will require to be built with debian-installer support)
Use Cases
Jon bought a new freescale pegatron netbook that he got without OS for only $150, he wants to install ubuntu on it, downloads a live rootfs from cdimage.ubuntu.com, fires up the image-merger tool he installed on his ubuntu desktop at home in which he then selects the proper kernel for his netbook. The tool asks him to plug in a USB key to be used for installation and within minutes Jon has a bootable USB key to install ubuntu from a livesystem on his new netbook.
Willy has a nokia n810. He wants to use an ubuntu installation on it. Willy downloads the ubuntu-alternate-arm.img from cdimage.ubuntu.com, writes this image to an SD card, boots his nokia device from it and installs ubuntu to the internal flash memory. During the installation Willy selects the n8x0 kernel flavour and after a reboot his tablet boots into ubuntu.
Design
The livefs.sh script from the livecd-rootfs package needs to grow a --skip-kernel option that suppresses the installation of kernel images in the squashed rootfs, so kernel-less rootfs images can be created.
An offline tool will be created that merges a downloadable squashfs with a kernel package for a selectable target board and writes the merged image file to a target device.
The ubuntu build servers will create debian-installer based images for armel that include all binary kernels for the possible target boards. The necessary armel related bits and pieces apart from the kernels are already available from debian.
The following set of images was discussed at UDS to be built for jaunty:
- live ubuntu-desktop (kernel-less)
- d-i ubuntu-server
Possible images, if we get community support and requests were discussed as well but are more likely to show up in a later cycle:
- live netbook-remix (needs GL support for the desktop launcher)
- live kubuntu
- live xubuntu
Future possible images are:
- live MID
- An extremely small image which would fit in flash and wouldn't require mass storage such as a SATA disk
Implementation
Installation from disk or flash devices as well as netbooted installs will be supported by debian-installer, the -desktop flavour as a default will be made avilable through an alternate image, optionally the user can select other flavours than desktop in the expert mode of debian-installer in this image, where tasksel is available to install all other possible flavours of ubuntu.
With the livecd-rootfs changes in place the build servers will be able to roll kernel-less squashfs images that will be provided for download. An offline GTK based tool will be written to select a target kernel and create an actual livefs. The mentioned tool will write the image to a target device (USB or SD card) as a final step.
Outstanding Issues
There are different bootloaders that can be used on ARM based systems, most common are uboot and redboot (JTAG based devices are out of scope, these have to be installed vendor side), currently it is up to the user to configure the bootloader to boot from the installation device. A possible solution that doesnt yet go into the image build could be provided by ARMSoftbootLoader but this is beyond the scope of this spec and probably rather a task for the jaunty+1 development cycle.
Specs/ARMImageSelection (last edited 2009-01-20 23:01:40 by p5098ed03)