FROM instruction sets the Base Image for subsequent instructions. As such, a valid Dockerfile must have
FROM as its first instruction. The image can be any valid image – it is especially easy to start by pulling an image from the Public Repositories.
FROM must be the first non-comment instruction in the Dockerfile.
FROM can appear multiple times within a single Dockerfile in order to create multiple images. Simply make a note of the last image ID output by the commit before each new
The tag or digest values are optional. If you omit either of them, the builder assumes a latest by default. The builder returns an error if it cannot match the tag value.