Each RUN command creates a new intermediate image container layer every time. We can avoid this by arranging all RUN command into single command.

Example: -

RUN apt-get update

RUN apt-get -y install httpd

RUN apt-get -y install curl

RUN apt-get -y install vim

This above command can be written in the structured way to reduce the number of layers.

RUN apt-get update \

&& apt-get -y install httpd \

&& apt-get -y install curl \

&& apt-get -y install vim