Docker Cookbook - Second Edition

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The format for the Dockerfile is as follows:

    INSTRUCTION arguments

Generally, instructions are given in uppercase, but they are not case-sensitive. They are evaluated in order. The # code phrase in the beginning is treated like a comment.

Let's take a look at the different types of instruction:

• FROM: This must be the first instruction of any Dockerfile, and sets the base image for subsequent instructions. By default, the latest tag is assumed to be the following:

       FROM  <image>

Alternatively, consider the following tag:

       FROM  <images>:<tag> 

There can be more than one FROM instruction in one Dockerfile to create multiple images.

If only the image names, such as fedora and Ubuntu, are given, then the images will be downloaded ...