GPG error when creating ubuntu latest image


Not sure if this is really a Docker question, or Ubuntu or perhaps Vagrant.

When a script inside a docker image that I’ve acquired starts up I get the following error message during apt-get update.

W: GPG error: xenial InRelease: Could not execute ‘apt-key’ to verify signature (is gnupg installed?)
W: The repository ‘ xenial InRelease’ is not signed.

(repeated a couple more times, with very similar output)

Has anyone else come across this before? After this step, all the apt-get install steps fail because they don’t have the correct key, unless you specify --allow-unauthenticated.

Many thanks,