public key error

W: GPG 오류: http://us.archive.ubuntu.com/ubuntu bionic-backports InRelease: Couldn't create temporary file /tmp/apt.conf.rVavhs for passing config to apt-key
E: The repository 'http://us.archive.ubuntu.com/ubuntu bionic-backports 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.

 

해결방법 : 권한이 없을 경우 나타나는 Error

 

chmod 777 /tmp