So my Dockerfile is written like so:
# set env vars for linux user
ENV LINUX_USER="kbuser"
...
... # other stuff
...
USER kbuser
But I would like to use
USER $LINUX_USER
So that I only have to write the username in one place in the file. But this doesn't work.
How can I get around this?
Thank you.
Use the ARG directive. As per docs:
ARG <name>[=<default value>]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.
So you can actually use ARG like so:
ARG user=kbuser
USER $user
And you can actually set the argument when building the docker image:
docker build --build-arg user=banana .
There is much more to it in the docs, so you better read thoroughly.
