There are times when running sudo apt-get update in Ubuntu will result in error messages such as the following:
sudo apt-get update
If these errors aren’t fixed, apt will have problems when installing or upgrading packages. For example:
sudo apt-get upgrade
The apt packaging system has a set of trusted keys that determine whether a package can be authenticated and therefore trusted to be installed on the system. Sometimes the system does not have all the keys it needs and runs into this issue. Fortunately, there is a quick fix. Each key that is listed as missing needs to be added to the apt key manager so that it can authenticate the packages.
Looking at the error above, apt is telling us that the following keys are missing. Notice that these are listed multiple times. Each unique key will only need to be added once.
To add these keys, run the following commands:
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys [your_key]
If the keys that your system is missing differs, simply replace the key at the end of the above command with your key and run it.
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