In my sources.list, I have all of my distribution targets specified as "stable." Note: I don't want "squeeze", I just want whatever is "stable" at a given time. Today that's squeeze, but when 7.0 happens, I just want to roll over.

Anyway, all of the repositories support the stable spec, but backports.debian.org does not. 1m $ q: why?

You used:
Should it perhaps be in the format:
Don't know: just a thought, based on my reading of http://wiki.debian.org/SourcesList

I think I'm boxing above my weight. If you go to http://backports.debian.org/debian-backports/dists/ you can see that both squeeze-backports and stable-backports directories exist and appear identical.

Just ignore me.

It's down to how the backports repo is set up. Something to do with the archive keyring. It should still work - i.e. what you see is a warning not a fatal error. I just tested it here and though I see the warning it still works, i.e. I can update the package listing and install packages...

The question remains however, in why on earth you'd want to use "stable" in your sources? It appears to be based on this incorrect assumption:
Which is not how it works. Stable releases don't just "roll over" from one release to the next. Using stable in your sources and expecting a seamless upgrade is a good way to achieve a broken system. Only the testing and unstable branches can upgrade in this manner. For stable, the roughly two year step from one release to another is a big step.

But don't take my word for it, read the release notes for Debian Squeeze: http://www.debian.org/releases/squee...inimal-upgrade

//edit: I almost forgot - packages from squeeze-backports won't automatically upgrade anyway - so what you're attempting is largely pointless... You have to specify the target release (-t) to install/upgrade packages.

caravel gave great advice and I have to second that. leaving you sources.list set to stable is just asking for trouble. When Wheezy becomes stable the internet will be all a buzz with the news. When that happens read the release notes and follow them as close as possible and you still may have problems. So before changing your sources.list to wheezy ASK questions after first reading the release notes.

backports are built for a particular release, hence squeeze-backports.

BTW as others have already stated you should always use the release names and not "stable".

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This is the answer that makes the most sense to me. It's possible to imagine that a backported package version could be the primary package version in the next release. That's really what the "testing" alias is for, I suppose.

I do disagree with the other comments about not using "stable". The documentation that you linked suggests to change the sources.list to the new version name, when doing an upgrade. That's exactly what happens in the repository with "stable," when a new release becomes available; the symlink gets changed. Anyway, a distribution upgrade would always be executed by hand and with fore-thinking -- so nobody's breaking any systems. But anyway, I think it's a separate discussion.

Thanks for the responses.

You're free to disagree, but I've seen countless threads where users end up with a broken mess when a new release occurs. They run a normal upgrade or they have their upgrades running as a cron job or attempt to install packages and it pulls in half of the new new release with it...

It's far better to use the release code name. And then plan your upgrade, while sticking with oldstable when the new release arrives. For all you know a certain package or kernel support for a certain piece of your hardware could vanish from a new release - you would need time to prepare for or work around for this.