What is the docker ARG instruction in the dockerfile?

[pangolinsos]

Docker documentation: https://docs.docker.com/engine/reference/builder/

ARG CODE_VERSION=latest
FROM base:${CODE_VERSION}

From the two instructions above you can see the ARG instruction is used to pass an argument to FROM. The ARG cannot be used after the FROM instruction.

Also see: What is the FROM instruction in a dockerfile?