apt-getでGPG errorが発生した時の対策[Ubuntu]
対策
chmod 1777 /tmp
経緯
dockerで立てたコンテナでapt-get updateを打ち込むと，
W: GPG error: http://ppa.launchpad.net/jonathonf/python-3.6/ubuntu xenial InRelease: Could not execute 'apt-key' to verify signature (is gnupg installed?) W: The repository 'http://ppa.launchpad.net/jonathonf/python-3.6/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. W: GPG error: https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1604/x86_64 Release: At least one invalid signature was encountered. W: The repository 'https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1604/x86_64 Release' 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. W: GPG error: https://developer.download.nvidia.com/compute/machine-learning/repos/ubuntu1604/x86_64 Release: At least one invalid signature was encountered. W: The repository 'https://developer.download.nvidia.com/compute/machine-learning/repos/ubuntu1604/x86_64 Release' 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. W: GPG error: http://security.ubuntu.com/ubuntu xenial-security InRelease: Could not execute 'apt-key' to verify signature (is gnupg installed?) W: The repository 'http://security.ubuntu.com/ubuntu xenial-security 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. W: GPG error: http://archive.ubuntu.com/ubuntu xenial InRelease: Could not execute 'apt-key' to verify signature (is gnupg installed?) W: The repository 'http://archive.ubuntu.com/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. W: GPG error: http://archive.ubuntu.com/ubuntu xenial-updates InRelease: Could not execute 'apt-key' to verify signature (is gnupg installed?) W: The repository 'http://archive.ubuntu.com/ubuntu xenial-updates 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. W: GPG error: http://archive.ubuntu.com/ubuntu xenial-backports InRelease: Could not execute 'apt-key' to verify signature (is gnupg installed?) W: The repository 'http://archive.ubuntu.com/ubuntu xenial-backports 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.
のエラーが出た．上のコマンドを打ち込むことで解決．