I\'m installing MongoDB on an Ubuntu 14.04 machine, using the instructions at: https://docs.mongodb.org/manual/tutorial/install-mongodb-on-ubuntu/
So I run:
You don't need to reinstall the mongo packages, but just change the key as following:
List the keys to confirm it is expired:
apt-key list | grep "expired:"
Replace the key:
sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 0xd68fa50fea312927
The number 0xd68fa50fea312927 is the current valid key id (expires at 2019-10-09), as you can check here.