What is the ARG instruction good for in Docker?
Experience Level: Senior
Tags: Docker
Answer
The ARG instruction defines a variable that users can pass at build-time to the builder with the docker build command using the --build-arg <varname>=<value> flag. If a user specifies a build argument that was not defined in the Dockerfile, the build outputs a warning.
A Dockerfile may include one or more ARG instructions. For example, the following is a valid Dockerfile:
FROM busybox
ARG user1
ARG buildno
# ...
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