Problem statement: I need to pull docker(projectA and projectB) from two different urls based on the arg provided.
ARG url=docker-local.artifactory.com/projectA #By default its for A. RUN echo ${url} FROM $url Ideal Solution:
docker build -t hello . should build docker of project A
docker build --build-arg url="docker-local.artifactory.com/projectB" -t hello . should build docker of project B.
Current Issue:
"base name ($url) should not be blank" Using the docs for reference, if you want to use ARG in FROM, ARG must be the first line in your Dockerfile (as reminded by koby.el's answer) and FROM must come immediately after. See this section for details.
This minimal Dockerfile works:
ARG url=docker-local.artifactory.com/projectA FROM $url Built using this command with a build arg:
docker build -t from --build-arg url=alpine:3.9 . [+] Building 0.1s (5/5) FINISHED => [internal] load build definition from Dockerfile 0.0s => => transferring dockerfile: 116B 0.0s => [internal] load .dockerignore 0.0s => => transferring context: 2B 0.0s => [internal] load metadata for docker.io/library/alpine:3.9 0.0s => CACHED [1/1] FROM docker.io/library/alpine:3.9 0.0s => exporting to image 0.0s => => exporting layers 0.0s => => writing image sha256:352159a49b502edb1c17a3ad142b320155bd541830000c02093b79f4058a3bd1 0.0s => => naming to docker.io/library/from The docs also show an example if you want to re-use the ARG value after the first FROM command:
ARG url=docker-local.artifactory.com/projectA FROM $url ARG url RUN echo $url 
Jumping into an old thread here...
But after wasting a few hours on this one I think its worth mentioning - if you want to pass the image for the FROM part, the ARG MUST be the first line in the Dockerfile!
Otherwise, you'll get the following error:
ERROR: failed to solve: base name (${BASE_IMAGE}) should not be blank
Using the following build file,
ARG VERSION=busybox:latest FROM $VERSION ARG VERSION RUN echo $VERSION Running with the default value
docker build -t test . Sending build context to Docker daemon 16.38kB Step 1/4 : ARG VERSION=busybox:latest Step 2/4 : FROM $VERSION latest: Pulling from library/busybox Running with value changed during build
docker build -t test --build-arg VERSION="ubuntu:20.04" . Sending build context to Docker daemon 16.38kB Step 1/4 : ARG VERSION=busybox:latest Step 2/4 : FROM $VERSION 20.04: Pulling from library/ubuntu 