CODE EXAMPLE FOR SHELL

install apt on ubuntu

FROM centos:8

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-*

#docker
RUN yum upgrade -y

#other commands