Failed to fetch https://packages.sury.org/php/dists/stretch/InRelease
When Executing in a Debian 9, $ apt update I get this error: W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://packages.sury.org/php stretch InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B188E2B695BD4743 W: Failed to fetch https://packages.sury.org/php/dists/stretch/InRelease The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B188E2B695BD4743 W: Some index files failed to download. They have been ignored, or old ones used instead. This is because the DPA has a new signing key . To resolve this problem you have to update the APT signing key, downloading the new key from the repositories: $ sudo wget -O /etc/apt/trusted.gpg.d/php.gpg https://packages.sury.org/php/apt.gpg