dpkg -l status codes: ii, rc, un, iU, iF explained

Each line of dpkg -l starts with a status column of two or three characters. The first character is what you asked for (desired action), the second is the package's current state, and an optional third flags an error. ii means "should be installed, is installed"; rc means "removed, but configuration files are still there".

First character: desired action

Second character: current state

Third character: error flag

R means reinstallation required; the package is broken and must be reinstalled.

Common combinations

dpkg -l | grep '^rc' | awk '{print $2}'                  # leftovers of removed packages
dpkg -l | grep '^rc' | awk '{print $2}' | xargs -r sudo dpkg --purge
dpkg -l | grep -E '^.[HUFWt]'                            # packages in an unfinished state
sudo dpkg --configure -a                                 # finish configuring them