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Please check the status of this specification in Launchpad before editing it. If it is Approved, contact the Assignee or another knowledgeable person before making changes.

• Launchpad entry: https://features.launchpad.net/distros/ubuntu/+spec/software-channels

• Packages affected: apt, aptitude, apt-setup, gnome-app-install, gdebi, adept, synaptic and all programs that handle apt sources and packages

Summary

In the beginning sources.list was a good idea. Right now, it is a point of pain for end users and maintainers. This spec will propose a flexible and versatile replacement, addressing many needs that I have seen as a person who gives support to users, as a third party source for Ubuntu packages and as someone who sees the bugs in apt and pain for mirror admins that this can resolve.

Rationale

Editing sources.list is cumbersome and error-prone. sources.list.d already makes this a bit easier, but still fails to recognize that a software channel is so much more than a sources.list entry.

• A software channel contains packages, maybe it has mirrors and there are many types of software channels.
• A software channel can be PGP signed
• A software channel contains software that should be easy to install via gnome-app-install
• Third party channels should be easy to create
• Distribution upgrades should be as easy as upgrading a channel entry via apt
• Sources.list can be commented, but comments aren't easily translatable

Use cases

• Steven is an Ubuntu user. He wants an easy way to add new software sources without editing configuration files
• Mark is an entrepreneur offering closed-source packages for Ubuntu. He wants to make it easy for users to install them
• Simon is a QA person. He wants to make sure that users are warned when using unofficial packages
• Colin is a distribution maintainer. He wants to make it easy to enable only a few components of his distribution by default but make it just as easy for end users to add other components
• Karl is a mirror admin, he wants to make sure users can use close mirrors of the things that are mirrored by his mirror network

Design

A 'software channel' should be easy to enable, also for third parties. Therefor it must be a single file, on which a user can double-click to install it. Fortunately we already have such files: .deb packages. A software channel can simply be a .deb package. No new software needs to be written for them: gdebi is already there for third party channels and Ubuntu channels can be easily upgraded.

Contents of the package

First and foremost, a channel contains software sources. While we're redesigning this: let's make them much more flexible as well.

This example shows it all:

• Support multiple channels in one file
• Mirrors integrated in the sources, both general and per-country mirrors
• Easy to mark disabled
• Unlike sources.list, these files are not to be edited. Making upgrades much easier.

[channel]
name=Ubuntu supported packages
name[nl]=Door Ubuntu ondersteunde pakketten
name[de]=....
name[fr]=....
key=GPGKEYIDHERE
enabled=True
release=dapper
components=main restricted

[binary]
default=http://archive.ubuntu.com/ubuntu  
mirror1=http://mirror.ubuntu.com/ubuntu
nl=http://nl.archive.ubuntu.com
us=http://us.archive.ubuntu.com
ca=http://ca.archive.ubuntu.com

[source]
you get the idea

[channel]
name=Ubuntu security updates
etc...

The default ubuntu install should install 7 channels: main+restricted (normal, updates, security), universe+multiverse (normal, updates, security) and dapper-commercial (not neccessarily in .channel files, apt-setup also needs to be modified). Only the normal and security channels for main+restricted should be enabled by default.

The .desktop files for gnome-app-install / adept-installer can also be integrated here. This way they can be disabled when the channel is disabled. Making the clumsy "show unsupported/commercial" entry obsolete. It also makes it easy for third parties to add files to gnome-app-install.

Adding keys this way is also easy. A graphical apt-key utility should be written. The postinst of the channel package can simply use this to install the key. The apt-key program and/or apt should be modified to emit warnings for third party channels.

Example postinst:

case "$1" in
    configure)
        if "$DISPLAY")
             gdebi --add-key /var/lib/channels/1265DEA2
        else
             apt-key add /var/lib/channels/1265DEA2
        fi
    ;;
esac

Implementation

Code

None yet

Data preservation and migration

Non-ubuntu entries in Sources.list should be converted upon upgrade. Ubuntu entries can be dropped.

Unresolved issues

BoF agenda and discussion

• A suggestion, in the channel file above, it lists a "components=main restricted" line. I think this line should be expanded with all the possible components in the repository ("components=main restricted universe multiverse"), with another line added "enabled=main restricted". In this manner, only one section is needed per repository, and another whole channel file does not need to be added to change which components are enabled. -Matt Kuiken, 07 Jan, 2007

Notes

• Software channels also have relationships to other software channels - should this be captured somehow?

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