CentOS 7:

As the user on the machine where the keys are that you want to migrate:
Export the public keys:

gpg -a –export >mypublickey.asc

Export the private keys:

gpg -a –export-secret-keys > myprivatekey.asc

Export you trust database:

gpg –export-ownertrust > mytrust.db

Copy the mypublickeys.asc, myprivatekeys.asc and mytrust.db to the new machine.

Log into the new machine as the user you want the keys for:
Import the private key file:

gpg –import myprivatekey.asc

Import the public key file:

gpg –import mypublickey.asc

List the secret keys to verify:

gpg -K

List the public keys to verify:

gpg -k

Import the trustdb:

gpg –import-ownertrust mytrust.db