If you want to mirror repositories from your current aptly server to a new server you must import the GPG key from your old server because you are going to encounter the following error:
gpgv: Signature made Fri 22 Apr 2019 17:35:04 AM UTC using DSA key ID FDC7A25E gpgv: Can't check signature: public key not found Looks like some keys are missing in your trusted keyring, you may consider importing them from keyserver: gpg --no-default-keyring --keyring trustedkeys.gpg --keyserver pool.sks-keyservers.net --recv-keys 181482CCFDC7A25E Sometimes keys are stored in repository root in file named Release.key, to import such key: wget -O - https://some.repo/repository/Release.key | gpg --no-default-keyring --keyring trustedkeys.gpg --import ERROR: unable to fetch mirror: verification of detached signature failed: exit status 2
And the mirror command fails. The problem is
you must import the GPG key from your old server in trustedkeys.gpg (even if you have already imported it in the new server with apt-key!!!)
Here is how to list, export and import it (we are going to import it in default and trustedkeys.gpg, because it is more convenient, but it is not mandatory to be in the default).
Keep on reading!