7.3 How can I tell what packages are already installed on a Debian system?

To learn the status of all the packages installed on a Debian system, execute the command

     dpkg --list

This prints out a one-line summary for each package, giving a 2-letter status symbol (explained in the header), the package name, the version which is installed, and a brief description.

To learn the status of packages whose names match the string any pattern beginning with "foo" by executing the command:

     dpkg --list 'foo*'

To get a more verbose report for a particular package, execute the command:

     dpkg --status packagename