Sudo apt update error

[yuke0915]

When I tried to update by “sudo apt update”, an error showed up.
sudo apt update

Get:4 http://packages.ros.org/ros2/ubuntu focal InRelease [4,685 B]
Err:4 http://packages.ros.org/ros2/ubuntu focal InRelease
The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY F42ED6FBAB17C654
Reading package lists… Done
W: GPG error: http://packages.ros.org/ros2/ubuntu focal InRelease: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY F42ED6FBAB17C654
E: The repository ‘http://packages.ros.org/ros2/ubuntu focal InRelease’ is not signed.
N: Updating from such a repository can’t be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

My JetPack is below.
Package: nvidia-jetpack
Version: 5.1.2-b104
Architecture: arm64
Maintainer: NVIDIA Corporation
Installed-Size: 194
Depends: nvidia-jetpack-runtime (= 5.1.2-b104), nvidia-jetpack-dev (= 5.1.2-b104)

Priority: standard
Section: metapackages
Filename: pool/main/n/nvidia-jetpack/nvidia-jetpack_5.1.2-b104_arm64.deb
Size: 29304
SHA256: fda2eed24747319ccd9fee9a8548c0e5dd52812363877ebe90e223b5a6e7e827
SHA1: 78c7d9e02490f96f8fbd5a091c8bef280b03ae84
MD5sum: 6be522b5542ab2af5dcf62837b34a5f0
Description: NVIDIA Jetpack Meta Package
Description-md5: ad1462289bdbc54909ae109d1d32c0a8

[whitesscott]

reference to documents to install Galactic ros2 for ubuntu focal

sudo apt update && sudo apt install curl

sudo curl -sSL https://raw.githubusercontent.com/ros/rosdistro/master/ros.key -o /usr/share/keyrings/ros-archive-keyring.gpg

[yuke0915]

Thank you. It worked!