In my Dockerfile I have the following:
ARG a-version
RUN wget -q -O /tmp/alle.tar.gz http://someserver/server/$a-version/a-server-$a-version.tar.gz && \
mkdir /opt/apps/$a-version
However when building this with:
--build-arg http_proxy=http://myproxy","--build-arg a-version=a","--build-arg b-version=b"
Step 10/15 : RUN wget... is shown with $a-version in the path instead of the substituted value and the build fails.
I have followed the instructions shown here but must be missing something else.
My questions is, what could be causing this issue and how can i solve
it?
Another thing to be careful about is that after every FROM statements all the ARGs get collected and are no longer available. Be careful with multi-stage builds.
You can reuse ARG with omitted default value inside FROM to get through this problem:
ARG VERSION=latest
FROM busybox:$VERSION
ARG VERSION
RUN echo $VERSION > image_version
Example taken from docs:
https://docs.docker.com/engine/reference/builder/#understand-how-arg-and-from-interact
Don't use - in variable names.
Docker build will always show you the line as is written down in the Dockerfile, despite the variable value.
So use this variable name a_version:
ARG a_version
See this example:
Dockerfile:
FROM alpine
ARG a_version
RUN echo $a_version
Build:
$ docker build . --build-arg a_version=1234
Sending build context to Docker daemon 2.048 kB
Step 1/3 : FROM alpine
---> a41a7446062d
Step 2/3 : ARG a_version
---> Running in c55e98cab494
---> 53dedab7de75
Removing intermediate container c55e98cab494
Step 3/3 : RUN echo $a_version <<< note this <<
---> Running in 56b8aeddf77b
1234 <<<< and this <<
---> 89badadc1ccf
Removing intermediate container 56b8aeddf77b
Successfully built 89badadc1ccf
I had the same problem using Windows containers for Windows.
Instead of doing this (Which works in linux containers)
FROM alpine
ARG TARGETPLATFORM
RUN echo "I'm building for $TARGETPLATFORM"
You need to do this
FROM mcr.microsoft.com/windows/servercore
ARG TARGETPLATFORM
RUN echo "I'm building for %TARGETPLATFORM%"
Just change the variable resolution according to the OS.
I spent much time to have the argument substitution working, but the solution was really simple. The substitution within RUN needs the argument reference to be enclosed in double quotes.
ARG CONFIGURATION=Debug
RUN dotnet publish "Project.csproj" -c "$CONFIGURATION" -o /app/publish
The only way I was able to substitute an ARG in a Windows Container was to prefix with $env:, as mentioned here.
An example of my Dockerfile is below. Notice that the ARG PAT is defined after the FROM so that it's in scope for its use in the RUN nuget sources add command (as Hongtao suggested). The only successful way I found to supply the personal access token was using $env:PAT
FROM mcr.microsoft.com/dotnet/framework/sdk:4.7.2 AS build
WORKDIR /app
ARG PAT
# copy csproj and restore as distinct layers
COPY *.sln .
COPY WebApi/*.csproj ./WebApi/
COPY WebApi/*.config ./WebApi/
RUN nuget sources add -name AppDev -source https://mysource.pkgs.visualstudio.com/_packaging/AppDev/nuget/v2 -username usern -password $env:PAT
RUN nuget restore
# copy everything else and build app
COPY WebApi/. ./WebApi/
WORKDIR /app/WebApi
RUN msbuild /p:Configuration=Release
FROM mcr.microsoft.com/dotnet/framework/aspnet:4.7.2 AS runtime
WORKDIR /inetpub/wwwroot
COPY --from=build /app/WebApi/. ./
The actual Docker command looks like this:
docker build --build-arg PAT=mypatgoeshere -t webapi .
I had the same problem accessing build-args in my RUN command. Turns out that the line containing the ARG definition should not be the first line. The working Dockerfile snippet looks like this:
FROM centos:7
MAINTAINER xxxxx
ARG SERVER_IPS
Earlier, I had placed the ARG definition as the first line of Dockerfile . My docker version is v19.
There are many answers, which make sense.
But the main thing is missed.
The way, how to use build arguments depends on the base image.
For Linux image, it will work with $ARG
For Windows, depending on image, it can be either $env:ARG(e.g. for mcr.microsoft.com/dotnet/framework/sdk:4.8) or %ARG% (e.g. for mcr.microsoft.com/windows/nanoserver:1809)
For me it was argument's order:
docker build . -f somepath/to/Dockerfile --build-arg FOO=BAR
did not work, but:
docker build --build-arg FOO=BAR . -f somepath/to/Dockerfile
did.
Related
Is it possible to copy from another image inside a dockerfile, using a variable as parameter of the from flag?
What I would achieve is the following
ARG MY_VERSION
COPY --from=my-image:$MY_VERSION /src /dst
But i always get
invalid from flag value my-image:$MY_VERSION: invalid reference format
You can do what you want, but you need to have a FROM statement identifying the image you want to copy from. Something like this
ARG MY_VERSION
FROM my-image:$MY_VERSION as source
FROM scratch as final
COPY --from=source /src /dst
Replace scratch with the base image you want to use for your new image.
Here's an example to show that it works. Dockerfile:
ARG MY_VERSION
FROM ubuntu:$MY_VERSION as source
FROM alpine:latest
COPY --from=source /etc/os-release /
Build and run with
docker build --build-arg MY_VERSION=20.04 -t test .
docker run --rm test cat /os-release
The output shows
NAME="Ubuntu"
VERSION="20.04.2 LTS (Focal Fossa)"
ID=ubuntu
...
which shows that it has copied a file from the Ubuntu 20.04 image to an Alpine image.
I am having difficulties with ARG & ENV in docker after I have upgraded to Docker version 20.10.7, build f0df350 on windows 10.
I have made dockerfile to show issue:
FROM microsoft/dotnet:2.2-aspnetcore-runtime AS base
ARG node_build=production
ENV node_build_env=${node_build}
FROM node:12.18.3 AS node-build
WORKDIR /root
RUN echo $node_build_env > test.txt
FROM base AS final
WORKDIR /app
COPY --from=node-build /root/test.txt ./
My goal here is that an ARG can be set and it will be then set as environment variable inside the container and if none is set it has a default value.
In this Dockerfile I am attempting to write the environment variable node_build_env to a text file then copy it to the final layer. The problem though is that the file is empty.
To re-create these are commands I am using:
docker build -t testargs:test .
docker run -it --rm testargs:test /bin/bash
cat test.txt
The file is empty. However if I run:
docker build -t testargs:test . --target node-build
and then manually run the command:
echo $node_build_env > test.txt
It works and the value production is written into the file.
Why does it work when I do it manually but not as part of the RUN command?
You are using multi-stage builds.
Your ARG & ENV belongs to base stage. And you're not using your base stage in your node-build build stage.
That means there is no node_build_env value in node-build. Hence the following line creates an empty test.txt file.
RUN echo $node_build_env > test.txt
However your final stage uses base stage. Which means it has access to node_build_env variable. So after building your image using docker build -t testargs:test . and then open up an interactive session with that container and try to execute the following command,
echo $node_build_env
You will see production will be printed out in the terminal.
I believe this will help you solve the problem. Cheers 🍻 !!!
edit:
this is working version:
ARG node_build=production
FROM microsoft/dotnet:2.2-aspnetcore-runtime AS base
FROM node:12.18.3 AS node-build
ARG node_build
ENV node_build_env=$node_build
WORKDIR /root
RUN echo $node_build_env > test.txt
FROM base AS final
WORKDIR /app
COPY --from=node-build /root/test.txt ./
Docker build tricky behavior:
Dockerfile
ARG php_version="7.2"
ARG flavor="stretch"
FROM php:${php_version}-fpm-${flavor}
#ARG php_version="7.2"
ENV php_v $php_version
CMD echo $php_v
If you build it and run:
docker build -t args:1.0 .
docker run -it --name testargs args:1.0
Output is empty string instead of the expected "7.2"
But if the third ARG line is uncommented we get "7.2"
Why does it behave this way?
Each FROM in a Dockerfile represents a new build stage and an ARG declared before the FROM is not available for use in the newer build stages starting with another FROM.
To quote the relevant section of the doc:
An ARG declared before a FROM is outside of a build stage, so it can’t
be used in any instruction after a FROM.
The problem is i cannot get the docker build arg value in the shell script while running the docker build.
My docker build command:
DOCKER_BUILDKIT=1 docker build --no-cache --progress=plain \
-t test \
--build-arg WHL_PATH=/fake/path \
.
Dockerfile
ARG WHL_PATH
FROM python:3.8.8
COPY test.sh .
RUN ./test.sh $WHL_PATH
and in the test.sh the "$1" is empty...., if in the Dockerfile i put some constant value then i will be able to see that value in the $1, but with docker build arg or set the build arg as ENV VAR are always empty...
Where am i doing wrong, how should i achieve this?
Docker version 20.10.5, build 55c4c88
Build args are scoped. Before the first FROM step they only apply to the FROM steps to adjust the image you use. Within each stage, an ARG step applies to the remaining steps within that stage. So the fix is to reorder your steps:
FROM python:3.8.8
COPY test.sh .
ARG WHL_PATH
RUN ./test.sh $WHL_PATH
Oops, i never realised the position of the ARG instruction matters, basically:
any ARG before the first FROM can be used in any FROM line
any ARG within a build stage (after a FROM) can be used in that build stage
After i moved the ARG WHL_PATH after the line FROM xxx it works perfectly, hope this can save some of your time in the future.
And i was inspired by this answer actually: https://stackoverflow.com/a/50292255/7658313
I use Docker Toolbox for windows (for compatibility issues) and in the Dockerfile I specify an ARG so that I can use it when building the image with --build-arg command. Inside the dockerfile I also have some COPY commands and there I would like to use my variable but when I run docker build --build-arg VERSION_APP=something . it does not translate the variable . I have already used $VERSION_APP or ${VERSION_APP} or %VERSION_APP%.
FROM alpine
MAINTAINER Marinos
ARG VERSION_APP
RUN apk update && apk add dos2unix
COPY script.sh /home/script.sh
RUN chmod a+x /home/script.sh
RUN dos2unix /home/script.sh
RUN sh /home/script.sh
COPY installation.txt /home/Desktop/${VERSION_APP}
UPDATE
It seems that you should pass the whole path to the variable you use that is how I got it working.
If you actually use the command below then it is expected not to work because the argument called VERSION_APP
docker build --build-arg myVar=something
So the command should be
docker build --build-arg VERSION_APP=something
And in Dockerfile it should be %VERSION_APP% also you may need to use ENV like below:
ARG VERSION_APP
ENV VERSION_APP ${VERSION_APP}