An error may occur when updating the apt deb package manager cache on Linux (Ubuntu or Debian distros):
$ apt-get updateW: There is no public key available for the following key IDs: 467B942D3A79BD29
W: GPG error: https://repo.mysql.com/apt/ubuntu focal InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 467B942D3A79BD29
The most common time this happens is after a new repository has been added to the /etc/apt/sources.list.
This error indicates that your Linux computer doesn’t have a public GnuPG repository key from which you are trying to install the package. The key hash is displayed directly in the error message. It is shown in this example: NO_PUBKEY 467B942D3A79BD29.
You must add this key to the apt database.
On Ubuntu, you can download the key from the key server (specify the key hash in the following command):
$ sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 467B942D3A79BD29
This is a key for MySQL, as seen in this example.
List the keys and check that a new key has been added:
$ apt-key list
On Debian, you can install a package with all the keys used to sign all the Release files:
$ apt-get install debian-archive-keyringIn my case, I got an error when trying to install the SQL Server package on Ubuntu:
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY EB3E94ADBE1229CF
W: GPG error: https://packages.microsoft.com/ubuntu/22.04/prod jammy InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY EB3E94ADBE1229CF
To install the Microsoft GPG keys, run the command:
curl -fsSL https://packages.microsoft.com/keys/microsoft.asc | sudo gpg --dearmor -o /usr/share/keyrings/microsoft-prod.gpg