- The build-time variables are passed as environment-context for command(s)
run as part of the RUN primitve. These variables are not persisted in environment of
intermediate and final images when passed as context for RUN. The build environment
is prepended to the intermediate continer's command string for aiding cache lookups.
It also helps with build traceability. But this also makes the feature less secure from
point of view of passing build time secrets.
- The build-time variables also get used to expand the symbols used in certain
Dockerfile primitves like ADD, COPY, USER etc, without an explicit prior definiton using a
ENV primitive. These variables get persisted in the intermediate and final images
whenever they are expanded.
- The build-time variables are only expanded or passed to the RUN primtive if they
are defined in Dockerfile using the ARG primitive or belong to list of built-in variables.
HTTP_PROXY, HTTPS_PROXY, http_proxy, https_proxy, FTP_PROXY and NO_PROXY are built-in
variables that needn't be explicitly defined in Dockerfile to use this feature.
Signed-off-by: Madhav Puri <madhav.puri@gmail.com>
parser_test only needed the directory-names for
the tests to run. This replaces f.Readdir() with
f.Readdirnames() to only return the names.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
If previous line ends with whitespace, or next line starts with whitepsace
we need to preserve a space otherwise things line:
RUN echo\
hello
will appear as: RUN echohello
Noticed this while looking at #5744 because he had lines ending in &&\
Signed-off-by: Doug Davis <dug@us.ibm.com>
