To list all packages installed on the system, from a terminal prompt enter:

dpkg -l

Depending on the amount of packages on your system, this can generate a large amount of output. Pipe the output through grep to see if a specific package is installed:

dpkg -l | grep apache2

Replace apache2 with any package name, part of a package name, or other regular expression.

To list the files installed by a package, in this case the ufw package, enter:

dpkg -L ufw

If you are not sure which package installed a file, dpkg -S may be able to tell you. For example:

dpkg -S /etc/host.conf 
base-files: /etc/host.conf

The output shows that the /etc/host.conf belongs to the base-files package.

	Many files are automatically generated during the package install process, and even though they are on the filesystem dpkg -S may not know which package they belong to.

You can install a local .deb file by entering:

sudo dpkg -i zip_2.32-1_i386.deb

Change zip_2.32-1_i386.deb to the actual file name of the local .deb file.

Uninstalling a package can be accomplished by:

sudo dpkg -r zip

	Uninstalling packages using dpkg, in most cases, is NOT recommended. It is better to use a package manager that handles dependencies, to ensure that the system is in a consistent state. For example using dpkg -r you can remove the zip package, but any packages that depend on it will still be installed and may no longer function correctly.