Description
Description
Docker provides limited inheritance of Dockerfile ARGs between build stages, as described here: https://docs.docker.com/build/building/variables/#scoping
Once a build argument is declared or consumed in a stage, it's automatically inherited by child stages.
This contradicts the Dockerfile reference https://docs.docker.com/reference/dockerfile/#scope - which states:
An ARG instruction goes out of scope at the end of the build stage where it was defined. To use an argument in multiple stages, each stage must include the ARG instruction.
Podman behaves according to the latter statement, making the examples given in the other document incompatible.
Steps to reproduce the issue:
Try to build a Containerfile with the following contents (copied from the Docker manual):
# syntax=docker/dockerfile:1
FROM alpine AS base
# Declare the build argument in the build stage
ARG NAME="joe"
# Create a new stage based on "base"
FROM base AS build
# The NAME build argument is available here
# since it's declared in a parent stage
RUN echo "hello $NAME!"
Describe the results you received:
podman build prints:
[2/2] STEP 2/2: RUN echo "hello $NAME!"
hello !
Describe the results you expected:
docker build would print:
[2/2] STEP 2/2: RUN echo "hello $NAME!"
hello joe!
Output of rpm -q buildah or apt list buildah:
buildah/testing,unstable,now 1.37.2+ds1-3 amd64 [installed,automatic]
Output of buildah version:
Version: 1.37.2
Go Version: go1.22.7
Image Spec: 1.1.0
Runtime Spec: 1.2.0
CNI Spec: 1.0.0
libcni Version:
image Version: 5.32.2
Git Commit:
Built: Thu Jan 1 01:00:00 1970
OS/Arch: linux/amd64
BuildPlatform: linux/amd64
Output of podman version if reporting a podman build issue:
Client: Podman Engine
Version: 5.2.2
API Version: 5.2.2
Go Version: go1.23.1
Built: Thu Jan 1 01:00:00 1970
OS/Arch: linux/amd64
Output of cat /etc/*release:
PRETTY_NAME="Debian GNU/Linux trixie/sid"
NAME="Debian GNU/Linux"
VERSION_CODENAME=trixie
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"
Output of uname -a:
Linux 6.10.9-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.10.9-1 (2024-09-08) x86_64 GNU/Linux
Output of cat /etc/containers/storage.conf:
cat: /etc/containers/storage.conf: No such file or directory