Apt Key Add Keysig
For some reason, recently, the Key used by ros is expiring frequently. E.g. when an warning like this when apt update:
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://packages.ros.org/ros/ubuntu bionic InRelease: The following signatures were invalid: EXPKEYSIG F42ED6FBAB17C654 Open Robotics <info@osrfoundation.org>
W: Failed to fetch http://packages.ros.org/ros/ubuntu/dists/bionic/InRelease The following signatures were invalid: EXPKEYSIG F42ED6FBAB17C654 Open Robotics <info@osrfoundation.org>
W: Some index files failed to download. They have been ignored, or old ones used instead.
This can be used to retrive the key from GPG for apt: (F42ED6FBAB17C654 is the Key Signature)
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys F42ED6FBAB17C654