Data from such a repository can't be authenticated and is therefore potentially dangerous to use.

hett@hett-virtual-machine:~$ sudo apt-key adv --keyserver hkp://ha.pool.sks-keyservers.net:80 --recv-key 0xB01FA116 Executing: /tmp/tmp.1Tl7mgE7Z7/gpg.1.sh --keyserver hkp://ha.pool.sks-keyservers.net:80 --recv-key 0xB01FA116 gpg: requesting key B01FA116 from hkp server ha.pool.sks-keyservers.net gpg: key B01FA116: public key "Totally Legit Signing Key " imported gpg: key B01FA116: public key "ROS Builder " imported gpg: Total number processed: 2 gpg: imported: 2 (RSA: 1) hett@hett-virtual-machine:~$ sudo apt-get update Hit:1 http://security.ubuntu.com/ubuntu xenial-security InRelease Hit:2 http://cn.archive.ubuntu.com/ubuntu xenial InRelease Hit:3 http://cn.archive.ubuntu.com/ubuntu xenial-updates InRelease Hit:4 http://cn.archive.ubuntu.com/ubuntu xenial-backports InRelease Get:5 http://packages.ros.org/ros/ubuntu xenial InRelease [4,678 B] Ign:5 http://packages.ros.org/ros/ubuntu xenial InRelease Get:6 http://packages.ros.org/ros/ubuntu xenial/main amd64 Packages [805 kB] Get:7 http://packages.ros.org/ros/ubuntu xenial/main i386 Packages [576 kB] Fetched 1,385 kB in 13s (103 kB/s) Reading package lists... Done W: GPG error: http://packages.ros.org/ros/ubuntu xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY F42ED6FBAB17C654 W: The repository 'http://packages.ros.org/ros/ubuntu xenial InRelease' is not signed. N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use. N: See apt-secure(8) manpage for repository creation and user configuration details. hett@hett-virtual-machine:~$ sudo apt-get update Get:1 http://packages.ros.org/ros/ubuntu xenial InRelease [4,678 B] Hit:2 http://security.ubuntu.com/ubuntu xenial-security InRelease Hit:3 http://cn.archive.ubuntu.com/ubuntu xenial InRelease Ign:1 http://packages.ros.org/ros/ubuntu xenial InRelease Hit:4 http://cn.archive.ubuntu.com/ubuntu xenial-updates InRelease Hit:5 http://cn.archive.ubuntu.com/ubuntu xenial-backports InRelease Fetched 4,678 B in 1s (3,021 B/s) Reading package lists... Done W: GPG error: http://packages.ros.org/ros/ubuntu xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY F42ED6FBAB17C654 W: The repository 'http://packages.ros.org/ros/ubuntu xenial InRelease' is not signed. N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use. N: See apt-secure(8) manpage for repository creation and user configuration details. hett@hett-virtual-machine:~$ sudo rm /var/lib/apt/lists/* -vf hett@hett-virtual-machine:~$ sudo apt-get update