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 before FROM, don't use anything in-between. 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
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