False Gems

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

So now we have the same issues that we had for Centos 6. And therefore we can fix it like it was described in previous post.

$ sed -i 's,baseurl=http://vault.centos.org,baseurl=http://vault.epel.cloud|g' /etc/yum.repos.d/CentOS-Linux-*

Alternative (AlmaLinux)

The issue with the fix above is that now we have a frozen repo that never will be updated. If your want to have the latest security updates you may consider a migration to one of Cento's successors. An AlmaLinux migration script is located here. Basically, it looks like this:

$ sudo dnf -y upgrade
$ curl -O https://raw.githubusercontent.com/AlmaLinux/almalinux-deploy/master/almalinux-deploy.sh
$ sudo bash almalinux-deploy.sh