builder: rephrase ENV section, remove examples for ENV key value without '=' #2741
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…out '='
The `ENV key value` form can be ambiguous, for example, the following defines
a single env-variable (`ONE`) with value `"TWO= THREE=world"`:
ENV ONE TWO= THREE=world
While we cannot deprecate/remove that syntax (as it would break existing
Dockerfiles), we should reduce exposure of the format in our examples.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
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silvin-lubecki
approved these changes
Sep 23, 2020
| RUN DEBIAN_FRONTEND=noninteractive apt-get update && apt-get install -y ... | ||
| ``` | ||
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| Or using [`ARG`](#arg), which is not persisted in the final image: |
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I don't think we should enforce that, I consider it more a trick than a real feature.
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It's a build-time argument/option, so I think it's a valid use, not different from, e.g.
ARG VERSION=v1.0.0
RUN install foo-${VERSION}There was a problem hiding this comment.
To me the ARG semantic is to expose a customization point to the user, not to set an env var only during build step. So yes it works, but should we advertise it in the doc?
tonistiigi
reviewed
Sep 23, 2020
docs/reference/builder.md
Outdated
| > ``` | ||
| > | ||
| > The alternative syntax is supported for backward compatibility, but discouraged | ||
| > for the reasons outlined above. |
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and may be removed in a future version.
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Opened #2743 if we want to officially deprecate
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
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tonistiigi
approved these changes
Sep 23, 2020
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relates to moby/buildkit#1692 (comment)
- What I did
The
ENV key valueform can be ambiguous, for example, the following definesa single env-variable (
ONE) with value"TWO= THREE=world":ENV ONE TWO= THREE=worldWhile we cannot deprecate/remove that syntax (as it would break existing
Dockerfiles), we should reduce exposure of the format in our examples.
- A picture of a cute animal (not mandatory but encouraged)