Debian’s “testing” distribution is where Debian developers prepare the next stable distribution. While this is still its main purpose, many users have adopted this version of Debian because it offers them a good trade-off between stability and freshness. But there are downsides to using this distribution and the “Constantly Usable Testing” (CUT) project aims to resolve those. This article will present the project and the challenges involved to make it happen. About Debian unstable & testing Debian unstable is the distribution where developers upload new versions of their packages.

It happens frequently that some packages are not installable due to changes in other packages or due to transitions not yet completed. Debian testing, on the contrary, is managed by a tool that ensures the consistency of the whole distribution: it picks updates from unstable only if the package has been enough tested (10 days usually), if it’s free of new release-critical bugs, if it’s available on all supported architectures, and if it doesn’t break any other package already present in testing. The Release Team (RT) controls this tool and provide “hints” to help it find a set of packages that can flow from unstable to testing. Those rules also ensure that the packages that flow into testing are reasonably free of show-stopper bugs (like a system that doesn’t boot, or X that doesn’t work at all). This makes it very attractive to users who like to regularly get new upstream versions of their software without dealing with the biggest problems associated to them. This is all very attractive, yet several Debian developers advise people to not use testing.

Known problems with testing Disappearing software The release team use this distribution to prepare the next stable release and from time to time they remove packages from it. Either because it’s needed to ensure that other packages can migrate from unstable to testing, or because they have long-standing release-critical bugs without progress towards a resolution. It also happens that they remove packages on request of the maintainers because they believe that the current version of the software cannot be supported (security-wise) for 2 years or more. The security team also regularly issues such requests. Long delays for security and important fixes Despite the 10-day delay in unstable, there are always some annoying bugs (and security bugs are no exceptions) that are only discovered when the package already has migrated to testing.

Package: debian-installer Severity: important Tags: d-i Dear Maintainer, I tried to install Debian Testing in a VM, which failed in the 'select and install software' step.

The maintainer might be quick to upload a fixed package in unstable, and might even raise the urgency to allow the package to migrate sooner, but if the packages gets entangled in a large ongoing transition, it will not migrate before the transition is completed. Sometimes it can take weeks for that to happen. This delay can be avoided by doing direct uploads to testing (through testing-proposed-updates) but this is almost never used, except during a freeze, where targeted bugfixes are the norm. Not always installable With testing evolving daily, updates sometimes break the last installation images available (in particular netboot images that get everything from the network).

The debian-installer (d-i) packages are usually quickly fixed but they don’t move to testing automatically because the new combination of d-i packages has not necessarily been validated yet. Sums up the problem: Getting new installer code into testing takes too long, and problems remain unfixed in testing for too long. [] The problem with d-i development at the moment is more that we’re very slow at producing new d-i *releases*. [] Your choices right now are to work with stable (too old), testing (would be nice except for the way sometimes it breaks and then it tends to take a week to fix anything), unstable (breaks all the time). CUT’s history CUT finds its root in an old: it introduces the idea that the stable release is not Debian’s sole product and that testing could become — with some work — a suitable choice for end-users.

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