Solving the problem on Failed to download metadata for repo 'appstream'

One new layer was added before run the yam update command:

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

RUN yum upgrade -y