A best-practice in Dockerfile’s is to use pipefail when commands pipe output of on into another as this ensures that an unexpected error prevents the build from inadvertently succeeding.
Not all shells such as the dash shell on Debian-based images don’t support the -o pipefail option, therefore it
should be considered to choose a different shell. This can be either done inside the RUN instruction or via SHELL
globally.
FROM debian:latest
RUN ["/bin/bash", "-c", "set -o pipefail && echo \"pipefail\" | false; true"]
FROM debian:latest
SHELL ["/bin/bash", "-o", "pipefail", "-c"]
RUN echo "pipefail" | false; true
When using podman images need to be build with --format docker argument, as the SHELL instruction is not part of the
OCI image specification. See containers/buildah#507 and
containers/podman#8477.
podman build .
# STEP 1/3: FROM debian:buster
# STEP 2/3: SHELL ["/bin/bash", "-o pipefail"]
# --> Using cache 32c10fe9f242ee2bd04a609c584930e0b649661a8cdb46cabc6c9ac9c72a55ae
# --> 32c10fe9f24
# STEP 3/3: RUN echo "pipefail" | false; true
# COMMIT
# WARN[0000] SHELL is not supported for OCI image format, [/bin/bash -o pipefail] will be ignored. Must use `docker` format
# --> 7c03fa37bcd
# 7c03fa37bcde083c8932f520b58bf8a7c39e38311bfa06fd8fee1668f6e88941
podman build . --format docker
# STEP 1/3: FROM debian:buster
# STEP 2/3: SHELL ["/bin/bash", "-o pipefail"]
# --> Using cache f9b0a46c87fa2839d53a54ac8c2f1878662b96b73f433043b07b00809b952ffa
# --> f9b0a46c87f
# STEP 3/3: RUN echo "pipefail" | false; true
# /bin/bash: line 0: /bin/bash: echo "pipefail" | false; true: invalid option name
# Error: error building at STEP "RUN echo "pipefail" | false; true": error while running runtime: exit status 2