Centos not support for update/upgrade

 INFO: Error: Failed to download metadata for repo 'AppStream': Cannot prepare internal mirrorlist: No URLs in mirrorlist

Run:

• sudo sed -i -e "s|mirrorlist=|#mirrorlist=|g" /etc/yum.repos.d/CentOS-*
• sudo sed -i -e "s|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g" /etc/yum.repos.d/CentOS-*
• link: https://www.cnblogs.com/axinno1/p/15884647.html

or

• sed -i 's/mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS-*
• sed -i 's|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g' /etc/yum.repos.d/CentOS-*
• link: https://www.tecmint.com/error-failed-to-download-metadata-for-repo-appstream/