Unable to build Image as it is asking some input
The docker build process is non-interactive. You have to find a way to make it not ask for anything. The way to do that is by creating the necessary config files and placing them in the correct locations through the Dockerfile before installing vsftpd. The questions are there simply for vsftpd to generate a/some configuration file[s] for itself. You create one beforehand and place it correctly using the copy command before run yum install. If vsftpd finds the valid config file[s], it won't ask for anything anymore.