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@@ -443,6 +443,8 @@ more `--add-host` flags. This example adds a static address for a host named
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### Squash an image's layers (--squash) **Experimental Only**
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+#### Overview
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+
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Once the image is built, squash the new layers into a new image with a single
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new layer. Squashing does not destroy any existing image, rather it creates a new
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image with the content of the squashed layers. This effectively makes it look
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@@ -457,3 +459,91 @@ space.
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storing two copies of the image, one for the build cache with all the cache
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layers in tact, and one for the squashed version.
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+#### Prerequisites
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+
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+The example on this page is using experimental mode in Docker 1.13.
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+
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+Experimental mode can be enabled by using the `--experimental` flag when starting the Docker daemon or setting `experimental: true` in the `daemon.json` configuration file.
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+
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+By default, experimental mode is disabled. To see the current configuration, use the `docker version` command.
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+
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+```none
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+
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+Server:
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+ Version: 1.13.1
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+ API version: 1.26 (minimum version 1.12)
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+ Go version: go1.7.5
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+ Git commit: 092cba3
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+ Built: Wed Feb 8 06:35:24 2017
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+ OS/Arch: linux/amd64
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+ Experimental: false
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+
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+ [...]
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+
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+```
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+
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+To enable experimental mode, users need to restart the docker daemon with the experimental flag enabled.
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+
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+#### Enable Docker experimental
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+
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+Experimental features are now included in the standard Docker binaries as of version 1.13.0. For enabling experimental features, you need to start the Docker daemon with `--experimental` flag. You can also enable the daemon flag via /etc/docker/daemon.json. e.g.
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+
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+```
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+
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+{
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+ "experimental": true
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+}
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+
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+```
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+Then make sure the experimental flag is enabled:
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+
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+```bash
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+
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+$ docker version -f '{{.Server.Experimental}}'
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+true
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+
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+```
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+
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+#### Build an image with `--squash` argument
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+
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+The following is an example of docker build with `--squash` argument
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+
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+```Dockerfile
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+
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+FROM busybox
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+RUN echo hello > /hello
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+RUN echo world >> /hello
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+RUN touch remove_me /remove_me
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+ENV HELLO world
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+RUN rm /remove_me
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+
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+```
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+An image named `test` is built with `--squash` argument.
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+
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+```bash
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+
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+$ docker build --squash -t test .
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+
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+[...]
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+
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+```
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+
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+If everything is right, the history will look like this:
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+
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+```bash
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+$ docker history test
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+
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+IMAGE CREATED CREATED BY SIZE COMMENT
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+4e10cb5b4cac 3 seconds ago 12 B merge sha256:88a7b0112a41826885df0e7072698006ee8f621c6ab99fca7fe9151d7b599702 to sha256:47bcc53f74dc94b1920f0b34f6036096526296767650f223433fe65c35f149eb
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+<missing> 5 minutes ago /bin/sh -c rm /remove_me 0 B
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+<missing> 5 minutes ago /bin/sh -c #(nop) ENV HELLO=world 0 B
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+<missing> 5 minutes ago /bin/sh -c touch remove_me /remove_me 0 B
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+<missing> 5 minutes ago /bin/sh -c echo world >> /hello 0 B
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+<missing> 6 minutes ago /bin/sh -c echo hello > /hello 0 B
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+<missing> 7 weeks ago /bin/sh -c #(nop) CMD ["sh"] 0 B
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+<missing> 7 weeks ago /bin/sh -c #(nop) ADD file:47ca6e777c36a4cfff 1.113 MB
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+
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+```
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+We could find that all layer's name is `<missing>`, and there is a new layer with COMMENT `merge`.
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+
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+Test the image, check for `/remove_me` being gone, make sure `hello\nworld` is in `/hello`, make sure the `HELLO` envvar's value is `world`.
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erxian