Overriding ARG in a build
The ARG Dockerfile instruction allows us to set a variable in a Dockerfile and then optionally override it when building an image. We've added a Dockerfile to your current working directory with the following instructions:
FROM ubuntu
ARG WELCOME_TEXT=Hello!
RUN echo $WELCOME_TEXT
CMD echo $WELCOME_TEXT
The Dockerfile adds an ARG named WELCOME_TEXT, which is then printed during the build. The same text is printed when a container is started from the image.
This exercise is part of the course
Introduction to Docker
Exercise instructions
- Using the terminal, enter the command to build the Dockerfile and set the
WELCOME_TEXT
variable toWelcome!
.
Hands-on interactive exercise
Turn theory into action with one of our interactive exercises
