DerekChia

DerekChia

$ docker build --no-cache -t demo-onbuild .

### REMOVED ###
Step 6/11 : RUN echo "First stage build time:"; env | grep VAR_
 ---> Running in 2059bd2e7860
First stage build time:
VAR_ARG=arg_value
VAR_ENV=env_value
Removing intermediate container 2059bd2e7860
 ---> ec2a853d2c02

DerekChia

# First stage
FROM debian as base
ENV VAR_ENV=env_value
ARG VAR_ARG=arg_value
ONBUILD ENV VAR_ENV_ONBUILD=onbuild_env_value
ONBUILD ARG VAR_ARG_ONBUILD=onbuild_arg_value
RUN echo "First stage build time:"; env | grep VAR_
# Second stage
FROM base
RUN echo "Second stage build time:"; env | grep VAR_

DerekChia

$ docker build --build-arg SOME_VAR=new-value --no-cache -t demo .

### REMOVED ###
Step 2/5 : ENV SOME_VAR=env-value
 ---> Running in 10d7cb325994
Removing intermediate container 10d7cb325994
 ---> dcab47c67952
Step 3/5 : ARG SOME_VAR=arg-value
 ---> Running in 265c48974673
Removing intermediate container 265c48974673

DerekChia

$ docker build --no-cache -t demo .

### REMOVED ###
Step 2/5 : ENV SOME_VAR=env-value
 ---> Running in ed8e108898e4
Removing intermediate container ed8e108898e4
 ---> 43da9e8e6dd6
Step 3/5 : ARG SOME_VAR=arg-value
 ---> Running in fb03d6097fb1
Removing intermediate container fb03d6097fb1

DerekChia

FROM ubuntu
ENV SOME_VAR=env-value
ARG SOME_VAR=arg-value
RUN echo "Build-time: SOME_VAR is set to ${SOME_VAR:-}"
CMD ["bash", "-c", "echo Run-time: SOME_VAR is set to ${SOME_VAR:-}"]

DerekChia

version: "3"
services:
  hello_world:
    container_name: ubuntu
    image: ubuntu:latest
    command: '/bin/sh -c "echo ${VARIABLE_ONE:-ONE}"'

DerekChia

version: "3"
services:
  hello_world:
    container_name: ubuntu
    image: ubuntu:latest
    environment:
      VARIABLE_ONE: ONE
    command: '/bin/sh -c "echo $$VARIABLE_ONE"'

DerekChia

version: "3"
services:
  hello_world:
    container_name: ubuntu
    image: ubuntu:latest
    command: '/bin/sh -c "echo $$VARIABLE_ONE"'

DerekChia

$ export VARIABLE_ONE=ONE