Fix Apt-Key Deprecation Error
sudo apt-key list
Depending on your system you may see a couple of entries appear or a veritable avalanche.
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pub rsa2048 2016-06-22 [SC]
D404 0146 BE39 7250 9FD5 7FC7 1F30 45A5 DF75 87C3
uid [ unknown] Skype Linux Client Repository <se-um@microsoft.com>
Copy the last 8 characters from the second line — in the example above this is DF75 87C3 — and convert it to a .gpg file using the command below. Remember to drop the space between the 8 characters and specify a gpg file name that is relevant to the package the key is for.
In my example I had to run:
sudo apt-key export DF7587C3 | sudo gpg --dearmour -o /etc/apt/trusted.gpg.d/skype.gpg
Once you’ve constructed your command hit enter …That’s all you need to do.
When you next run an apt update the deprecated key error will no longer appear for the repo you just applied (though if you have more than one repo affected, you’ll need to repeat the steps above for each one).