当我尝试更新 Ubuntu Server 18.04.4 时，存储库返回错误，我无法更新服务器。
root# apt update
Err:1 https://artifacts.elastic.co/packages/7.x/apt stable InRelease
Unknown error executing apt-key
Err:3 http://ap-south-1.ec2.archive.ubuntu.com/ubuntu bionic InRelease
Unknown error executing apt-key
Err:4 http://ap-south-1.ec2.archive.ubuntu.com/ubuntu bionic-updates InRelease
Unknown error executing apt-key
Reading package lists... Done
W: GPG error: https://artifacts.elastic.co/packages/7.x/apt stable InRelease: Unknown error executing apt-key
E: The repository 'https://artifacts.elastic.co/packages/7.x/apt stable 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.
W: GPG error: http://apt.postgresql.org/pub/repos/apt bionic-pgdg InRelease: Unknown error executing apt-key
E: The repository 'http://apt.postgresql.org/pub/repos/apt bionic-pgdg 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.