List all installed packages:

1$ dpkg -l

List all recently installed packages:

1$ zcat -f /var/log/dpkg.log* | grep "\ install\ " | sort

Show the changelog of a package (here, the linux kernel of Ubuntu):

1$ aptitude changelog linux-generic

Which package contain a given file:

1$ apt-file search file_to_search

Get the list of files of a package:

1$ apt-file list package_name

Extract content of a package:

1$ ar vx mypackage.deb

Install a package from a lower-priority repository, like the backport repository:

1$ apt-get -t squeeze-backports install my-package

Force reinstallation of a package:

1$ apt-get -d --reinstall install my-package
2$ dpkg --install --force-confmiss /var/cache/apt/archives/my-package.deb

Upgrade package listing and metadata:

1$ sudo apt update

Force yes so that package maintainer’s version of config files always prevails:

1$ sudo apt upgrade -y --force-yes

Hold a package with either dpkg or aptitude :

1$ echo "kdenlive hold" | dpkg --set-selections

or:

1$ aptitude hold kdenlive

Unhold a package:

1$ echo "kdenlive install" | dpkg --set-selections

or:

1$ aptitude unhold kdenlive

List held packages:

1$ dpkg --get-selections | grep hold

Uninstall a package thoroughly (both program files and configuration):

1$ apt-get remove --purge my_package

Force removal of a package while ignoring all dependencies:

1$ dpkg --remove --force-depends libsomething

Remove orphaned packages:

1$ deborphan | xargs apt-get -y remove --purge

Clean aptitude local cache:

1$ apt-get clean

Remove dpkg lock file:

1$ rm /var/lib/dpkg/lock