An error occurred during the signature verification in the ROS function pack warehouse

When we install the ros-related packages or perform sudo apt-get update on a linux system with ros installed, the following error will occur:

Get:1 http://packages.ros.org/ros/ubuntu focal InRelease [4,676 B]
Hit:2 http://ports.ubuntu.com/ubuntu-ports focal InRelease
Hit:3 http://ports.ubuntu.com/ubuntu-ports focal-updates InRelease
Hit:4 http://ports.ubuntu.com/ubuntu-ports focal-backports InRelease
Err:1 http://packages.ros.org/ros/ubuntu focal InRelease
The following signatures were invalid: EXPKEYSIG F42ED6FBAB17C654 Open Robotics [email protected]
Hit:5 http://ports.ubuntu.com/ubuntu-ports focal-security InRelease
Fetched 4,676 B in 4s (1,078 B/s)
Reading package lists… Done
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 focal InRelease: The following signatures were invalid: EXPKEYSIG F42ED6FBAB17C654 Open Robotics [email protected]
W: Failed to fetch http://packages.ros.org/ros/ubuntu/dists/focal/InRelease The following signatures were invalid: EXPKEYSIG F42ED6FBAB17C654 Open Robotics [email protected]
W: Some index files failed to download. They have been ignored, or old ones used instead.

Why does this error occur?
ROS uses the debian package management system to distribute software, so it needs a GPG key to ensure the accuracy and authority of the package, usually the default key expires after about 2 years, so we need to add a new ros related key to it.

How to fix it
Download the certificate and add it.

curl -s https://raw.githubusercontent.com/ros/rosdistro/master/ros.key
sudo apt-key add ./ros.key

After the installation is successful, the log information of OK will be displayed.

$ sudo apt update
...
 Get:15 http://packages.ros.org/ros/ubuntu focal InRelease [4,676 B] 
...
 Fetched 2,671 kB in 2s (1,607 kB/s)                     
 Reading package lists… Done
 Building dependency tree       
 Reading state information… Done
 30 packages can be upgraded. Run 'apt list --upgradable' to see them.


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