You can check which processes are running with:
Originally Posted by runandjump
ps -u username
ps -u root
For instance, the Add/Remove app is listed as "gnome-app-insta" under my username, and Synaptic is listed as "synaptic" when searched for with the 'root' variation above.
Added: Should you find any listed under the root command, you can kill the process with:
For those found with your username, you don't need to add the "sudo". Interestingly, the identified processes are sometimes truncated, so gnome-app-insta is actually killed by the command:
sudo killall appname_or_process