On Sat, Jul 08, 2017 at 09:08:43AM +0800, 積丹尼 Dan Jacobson wrote: > This will affect the default candidate version of packages > according to the rules described in apt_preferences(5).
and a bit more explicit > This corresponds to the configuration item APT::Default-Release. explain why that isn't a bug (at least in my eyes, not the maintainer), but working as documented. You can use -t on apt-cache policy as well btw, which will show you the explicit and implicit pinnings involved and helps understanding the rules outlined in apt_preferences(5). The simple gist is: You can use -t and it will work if the version in the target release is >= installed version, but it will not downgrade to versions < installed version. You have to apply extra force if you really want that (pkg/release), but note that downgrading packages isn't officially supported by Debian so you might end up with a broken system if you downgrade the wrong package. Note also that the downgrade behaviour would be very strange for users who have the option always set (sometimes by default by their distro) as you couldn't install packages from another release (and that includes experimental, backports, …) without constantly being nagged to downgrade again to the default release. Horrible behaviour that would be… So, I don't think that deserves a special mention here as there is nothing special about it. That said, apt is a bit more explicit here but still "wrong" if you don't read the documentation it points to as we can't just embed everything everywhere. Its a manpage and not a manbook after all (through, manmovie might be the better analogy as those tend to be strictly sequential with limited outside references (with a few notable exceptions of course) while manbook is just pointing at size): | -t, --target-release, --default-release | This option controls the default input to the policy engine; it | creates a default pin at priority 990 using the specified release | string. This overrides the general settings in /etc/apt/preferences. | Specifically pinned packages are not affected by the value of this | option. In short, this option lets you have simple control over which | distribution packages will be retrieved from. Some common examples | might be -t '2.1*', -t unstable or -t sid. Configuration Item: | APT::Default-Release; see also the apt_preferences(5) manual page. Best regards David Kalnischkies
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