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Merge pull request #32362 from tonistiigi/multi-stage-build-docs

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Add docs for multi-stage builds
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Vincent Demeester 2017-04-10 14:26:08 +02:00 committed by GitHub
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1 changed files with 26 additions and 13 deletions
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docs/reference/builder.md
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@ -480,30 +480,36 @@ the first pattern, followed by one or more `!` exception patterns.
## FROM
FROM <image>
FROM <image> [AS <name>]
Or
FROM <image>:<tag>
FROM <image>[:<tag>] [AS <name>]
Or
FROM <image>@<digest>
FROM <image>[@<digest>] [AS <name>]
The `FROM` instruction sets the [*Base Image*](glossary.md#base-image)
for subsequent instructions. As such, a valid `Dockerfile` must have `FROM` as
its first instruction. The image can be any valid image – it is especially easy
to start by **pulling an image** from the [*Public Repositories*](https://docs.docker.com/engine/tutorials/dockerrepos/).
The `FROM` instruction initializes a new build stage and sets the
[*Base Image*](glossary.md#base-image) for subsequent instructions. As such, a
valid `Dockerfile` must have `FROM` as its first instruction. The image can be
any valid image – it is especially easy to start by **pulling an image** from
the [*Public Repositories*](https://docs.docker.com/engine/tutorials/dockerrepos/).
- `FROM` must be the first non-comment instruction in the `Dockerfile`.
- `FROM` can appear multiple times within a single `Dockerfile` in order to create
multiple images. Simply make a note of the last image ID output by the commit
before each new `FROM` command.
- `FROM` can appear multiple times within a single `Dockerfile` in order to
create multiple images or use one build stage as a dependency for another.
Simply make a note of the last image ID output by the commit before each new
`FROM` command. Each `FROM` command resets all the previous commands.
- The `tag` or `digest` values are optional. If you omit either of them, the builder
assumes a `latest` by default. The builder returns an error if it cannot match
the `tag` value.
- Optionally a name can be given to a new build stage. That name can be then
used in subsequent `FROM` and `COPY --from=<name|index>` commands to refer back
to the image built in this stage.
- The `tag` or `digest` values are optional. If you omit either of them, the
builder assumes a `latest` tag by default. The builder returns an error if it
cannot match the `tag` value.
## RUN
@ -937,6 +943,13 @@ All new files and directories are created with a UID and GID of 0.
> If you build using STDIN (`docker build - < somefile`), there is no
> build context, so `COPY` can't be used.
Optionally `COPY` accepts a flag `--from=<name|index>` that can be used to set
the source location to a previous build stage (created with `FROM .. AS <name>`)
that will be used instead of a build context sent by the user. The flag also
accepts a numeric index assigned for all previous build stages started with
`FROM` command. In case a build stage with a specified name can't be found an
image with the same name is attempted to be used instead.
`COPY` obeys the following rules:
- The `<src>` path must be inside the *context* of the build;