I have set up an Ubuntu local mirror server for the Focal(20.04) distribution using apt-mirror. Below are the configurations in /etc/apt/mirror.list:
deb http://archive.ubuntu.com/ubuntu focal main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu focal-security main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu focal-updates main restricted universe multiverse
After successfully updating apt-mirror, I can update and upgrade on client machines. However, I also desire support for distribution upgrades using the sudo do-release-upgrade command. To facilitate this, I've created a directory structure within focal/main named dist-upgrader-all/current/ and downloaded all necessary files, such as focal.tar.gz and focal.tar.gz.gpg, from archive.ubuntu.com.
Upon executing sudo do-release-upgrade from a client machine, I encounter the following error:
Checking for a new Ubuntu release
Get:1 Upgrade tool signature [1,554 B]
Get:2 Upgrade tool [1,338 kB]
Fetched 1,340 kB in 0s (0 B/s)
authenticate 'focal.tar.gz' against 'focal.tar.gz.gpg'
Authentication failed
Authenticating the upgrade failed. There may be a problem with the network or with the server.
I seek assistance in resolving this issue. Note: As we don't have internet connection on client machine so everything want to pull from mirror server only.
