Packages are manually installed via the
dpkg command (Debian Package Management System).
dpkg is the backend to commands like
aptitude, which in turn are the backend for GUI install apps like the Software Center and Synaptic.
Something along the lines of:
aptitude --> Synaptic, Software Center
But of course the easiest ways to install a package would be, first, the GUI apps (Synaptic, Software Center, etc..), followed by the terminal commands
aptitude that add a very nice user friendly approach to the backend dpkg, including but not limited to packaged dependencies, control over what is installed, needs update, not installed, broken packages, etc.. Lastly the
dpkg command which is the base for all of them.
Since dpkg is the base, you can use it to install packaged directly from the command line.
Install a package
sudo dpkg -i DEB_PACKAGE
For example if the package file is called
askubuntu_2.0.deb then you should do
sudo dpkg -i askubuntu_2.0.deb. If
dpkg reports an error due to dependency problems, you can run
sudo apt-get install -f to download the missing dependencies and configure everything. If that reports an error, you'll have to sort out the dependencies yourself by following for example How do I resolve unmet dependencies after adding a PPA?.
Remove a package
sudo dpkg -r PACKAGE_NAME
For example if the package is called
askubuntu then you should do
sudo dpkg -r askubuntu.
Reconfigure an existing package
sudo dpkg-reconfigure PACKAGE_NAME
This is useful when you need to reconfigure something related to said package. Some useful examples it the
keyboard-configuration when you want to enable the Ctrl+Alt+Backspace in order to reset the X server, so you would the following:
sudo dpkg-reconfigure keyboard-configuration
Another great one is when you need to set the Timezone for a server or your local testing computer, so you use use the
sudo dpkg-reconfigure tzdata