docker内でyumがつながらない時

こんなのが出るとき

[root@18e0c0c7298f server]# yum install -y libnsl
Failed to set locale, defaulting to C.UTF-8
CentOS Linux 8 - AppStream 41 B/s | 38 B 00:00
Error: Failed to download metadata for repo 'appstream': Cannot prepare internal mirrorlist: No URLs in mirrorlist

以下のコマンドで解決

sed -i 's|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g' /etc/yum.repos.d/CentOS-Linux-*;