(Resolved) Key is stored in legacy trusted.gpg Keyring

I recently created a new Ubuntu 22.04 LTS Linux virtual machine. When I attempted to set up the PostgreSQL server on it, I saw a warning message like the one shown below on the screen:

Even after the warning message appeared, I was able to continue working. The way in which GPG keys are stored has been updated by the Debian developers, enhancing system security. You will notice this issue with Ubuntu 22.04 and Debian 11 systems.

The steps below will help you to move the key to a new location:

1. The first step is to find out the key id. You can list all the existing keys under trusted.gpg with the following command.

   sudo apt-key list 
   

   Warning: apt-key is deprecated. Manage keyring files in trusted.gpg.d instead (see apt-key(8)).
   /etc/apt/trusted.gpg
   --------------------
   pub   rsa4096 2011-10-13 [SC]
         B97B 0AFC AA1A 47F0 44F2  44A0 7FCC 7D46 ACCC 4CF8
   uid           [ unknown] PostgreSQL Debian Repository
   

2. I need to fix issue for the PostgreSQL repository. So copy the last 8 characters of the key ID and export it with the following command.

   sudo apt-key export ACCC4CF8 | sudo gpg --dearmour -o /usr/share/keyrings/pgdg.gpg 
   

3. Now edit the Apt repository configuration file like: /etc/apt/sources.list.d/pgdg.list. Add the singed-by tag with the above exported key file, like:

   deb [arch=amd64 signed-by=/usr/share/keyrings/pgdg.gpg] http://apt.postgresql.org/pub/repos/apt/ jammy-pgdg main
   

4. Now you can delete the key from trusted.gpg:

   sudo apt-key del ACCC4CF8 
   

Hopefully, this quick how-to tutorial helps you to resolve your issues. You can also follow the same instructions to resolve similar issues in other repositories.