Issue updating DGX OS 4

Accelerated Computing DGX Systems (Data Center)
1

Hello, I’m trying to upgrade the DGX OS version from 4 to 5 (and then eventually to the latest version). I’ve been following the instructions here: Upgrading — NVIDIA DGX OS 5 User Guide but am running into an error when trying to update OS 4 to the latest version. When I run sudo apt update, I get this error. Any help you can provide would be appreciated!

W: GPG error: https://international.download.nvidia.com/dgxstation/repos/bionic bionic-r418+cuda10.1 InRelease: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 208CE844D9F220AD
W: The repository ‘http://international.download.nvidia.com/dgxstation/repos/bionic bionic-r418+cuda10.1 InRelease’ is not signed.
N: Data from such a repository can’t be authenticated and is therefore potentially dangerous to use.

2

DGX OS 4 is now fairly old. Would it also be possible to back up the system and re-image a more recent release, such as 7.4?
For the particular issue, there was a change that required to rotated the keys. You can find more information here:

Please let me know if you have already done that so I can investigate further.