How can you completely remove a package? (in Ubuntu)

Use the command:

sudo apt-get purge --auto-remove packagename

另外可以用這個 command 找出已經被反安裝的 package:

dpkg --get-selections | grep -i deinstall | more

再用這個 command 把它清乾淨: (最上面那個 command 也行)

sudo apt purge packagename

ref: How can you completely remove a package?