If you ever get the following message in connection with the Google Modpagespeed module during an
apt update
on a Linux system:
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: stable Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6494C6D6997C215E
W: Failed to fetch http://dl.google.com/linux/mod-pagespeed/deb/dists/stable/Release.gpg The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6494C6D6997C215E
W: Some index files failed to download. They have been ignored, or old ones used instead.
Then execute the following line on the console and you have peace again 🙂.
wget -q -O - https://dl.google.com/linux/linux_signing_key.pub | sudo apt-key add -
