How can you unhold (remove a hold on) a package?

You can use sudo apt-mark unhold package_name. The package is unheld and it returns a confirmation: Canceled hold on package_name..

To unhold all held packages you can use sudo apt-mark unhold $(apt-mark showhold).

The correct way to remove the hold should be:

echo "package_name install"|sudo dpkg --set-selections

To unhold all held packages, use this command:

apt-mark unhold $(apt-mark showhold)