solved apt gpg error no pubkey

dealing with the "gpg error: no_pubkey" issue in apt (the package management tool in debian and ubuntu-based systems) is a common scenario when adding new repositories. this error occurs when the system cannot verify the authenticity of the packages due to a missing gpg key. below is a detailed tutorial on how to resolve this issue, along with code examples.

what is the "no_pubkey" error?

when you add a new repository to your apt sources, the repository might be signed with gpg keys. if your system does not have the public key associated with that repository, you will encounter the "no_pubkey" error when trying to update or install packages from that repository.

step-by-step guide to fix the "no_pubkey" error

step 1: identify the missing key

when you run an apt command (like `apt update`), you might see an error message similar to this:

```
```

in this case, `abc1234567890def` is the key you need to add.

step 2: add the missing gpg key

here are two methods to add the key:

method 1: using `apt-key`

```bash
replace abc1234567890def with your actual missing key
```

method 2: using `gpg` and `tee`

```bash
replace abc1234567890def with your actual missing key
```

step 3: update apt

once you have added the missing key, you should update apt to refresh the package lists:

```bash
sudo apt update
```

step 4: verify the fix

after running the update c ...

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