This short tutorial shows you how to list all the installed dpkg packages on Debian (all versions). On most systems (depending on configuration) you do not need root permissions to run this command.
How to list all installed packages on Debian
On the command line enter the following command:
This will dump all the installed packages onto the console, you might want to use less or more to limit the output.
Alternatively if you are looking for a specific package then enter:
The example above uses php as a package example you can replace this with any other package name apache2, awk, etc.