After upgrading to Ubuntu 22.04 running apt shows an error message saying “Key is stored in legacy trusted.gpg keyring“:
# apt update [..] All packages are up-to-date. W: https://apt.syncthing.net/dists/syncthing/InRelease: Key is stored in legacy trusted.gpg keyring (/etc/apt/trusted.gpg), see the DEPRECATION section in apt-key(8) for details.
The key needs to be exported from the legacy keyring and then imported back to the current system.
List the keys and find the key ID of the repository that is showing the error. In this case it is Syncthing.
# apt-key list -------------------- pub rsa2048 2014-12-29 [SC] 37C8 4554 E7E0 A261 54E7 6E1E D26E 6ED0 0065 5A3E uid [ unknown] Syncthing Release Management <email@example.com> sub rsa2048 2014-12-29 [E] /etc/apt/trusted.gpg.d/ubuntu-keyring-2012-cdimage.gpg [...]
Copy the last 8 characters of the key (00655A3E) and export it.
# apt-key export 00655A3E | gpg --dearmour -o /usr/share/keyrings/syncthing.gpg
Update the source file for the repository adding the exported key.
# vim /etc/apt/sources.list.d/syncthing.list deb [arch=amd64 signed-by=/usr/share/keyrings/syncthing.gpg] https://apt.syncthing.net/ syncthing stable #Syncthing
Confirm that the error message is no longer showing.
# apt update [...] Hit:5 https://apt.syncthing.net syncthing InRelease [...] Reading package lists... Done Building dependency tree... Done Reading state information... Done All packages are up-to-date.
Finally, remove the old signature.
# apt-key del 00655A3E