Merge pull request #970 from cowlinator/temp2

Clarify --build-arg documentation
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Sebastiaan van Stijn 2018-04-13 18:54:16 -07:00 committed by GitHub
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@ -411,13 +411,13 @@ files. The `ARG` instruction lets Dockerfile authors define values that users
can set at build-time using the `--build-arg` flag: can set at build-time using the `--build-arg` flag:
```bash ```bash
$ docker build --build-arg HTTP_PROXY=http://10.20.30.2:1234 . $ docker build --build-arg HTTP_PROXY=http://10.20.30.2:1234 --build-arg FTP_PROXY=http://40.50.60.5:4567 .
``` ```
This flag allows you to pass the build-time variables that are This flag allows you to pass the build-time variables that are
accessed like regular environment variables in the `RUN` instruction of the accessed like regular environment variables in the `RUN` instruction of the
Dockerfile. Also, these values don't persist in the intermediate or final images Dockerfile. Also, these values don't persist in the intermediate or final images
like `ENV` values do. like `ENV` values do. You must add `--build-arg` for each build argument.
Using this flag will not alter the output you see when the `ARG` lines from the Using this flag will not alter the output you see when the `ARG` lines from the
Dockerfile are echoed during the build process. Dockerfile are echoed during the build process.