Each unique key will only need to be added once. Notice that these are listed multiple times.

Looking at the error above, apt is telling us that the following keys are missing: 40976EAF437D05B5 and 3B4FE6ACC0B21F32. Each key that is listed as missing needs to be added to the apt key manager so that it can authenticate the packages. Sometimes the system does not have all the keys it needs and runs into this issue. 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. For example: $ sudo apt-get upgradeĮ: Some packages could not be authenticated If these errors aren’t fixed, apt will have problems when installing or upgrading packages. W: GPG error: trusty-updates Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32 W: GPG error: trusty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32 W: GPG error: trusty-security Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32 There are times when running apt-get update in Ubuntu will result in error messages such as the following: $ sudo apt-get update

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