monline

One thing about APT pinning I've now learned for life is that you should always check the output of apt-cache policy. In various distributions and APT versions the pinning might behave a bit differently. Checking the output of apt-cache policy (note that there's no package name at the end of the command, thus it'll list your APT sources and their pinning values) reveals most probably the reason why your preferences file does not do whatever you wish it to do.

Googling in the subject shows that you can downgrade PHP packages to Lenny versions without much trouble. However the already documented methods lacked a few things I consider important, thus I write down my own downgrade instructions for future reference.

I don't know of a simple APT command that could give the answer to the question of this post, thus I made a little awk script to filter the output of apt-cache policy to get what I want.

During upgrades between releases of a Debian (or Ubuntu) system you can end up with a lot of trash ... packages left over from earlier releases. Using the following command you can find packages that are not available from any of the APT repositories you've configured in /etc/apt/sources.list (or /etc/apt/sources.list.d/*):

These packages might have been manually installed or are remnants of a previous OS release. You should review the list and decide for yourself whether to keep them or purge them.

Note that the above command does not show packages for which the current version was manually installed from a DEB, but the package is available from a repository too.

For a more thorough list (packages for which the currently installed version is not from a repository ... including packages for which an update is available from the respective repository), try this:
(Don't forget to upgrade all packages to the current latest version or they'll be listed too.)

The command is: apt-cache policy packagename
Example output for the "thunderbird" package on an up-to-date Ubuntu Karmic system:

Aptitude (an APT front-end) has long been able to distinguish between packages as being automatically installed (based on some dependancy that another package required) or "manually" installed. Since Debian Lenny (5.0) this capability is integrated into the APT package management system and most probably Aptitude's functionality got a lot thinner (since it doesn't have to implement something that's already in APT's core).
I could not find a method to do this (ie. list the manual/auto installed status of packages) the APT-way, but Aptitude's search function does it well enough.
Here's the command to list automatically installed packages:
And the trivial opposite (list of manually installed packages):

Feisty got its End-Of-Life statement and it also means that the official Feisty repository was moved from http://archive.ubuntu.com/ to http://old-releases.ubuntu.com/. If you don't know what's going on and just run apt-get update, you'll see error messages like this ...

The basic method (I mean with default tools on a Debian system) is to use apt-cache:
However I've found that this does not always give correct results.

You can find the details here.

You can find the answer in this post, but I also document it here so I'll have a permanent copy.