From 82c23208eeba822473d444221399a7102479a702 Mon Sep 17 00:00:00 2001 From: Per Lundberg Date: Thu, 12 Apr 2018 11:58:13 +0300 Subject: [PATCH] build.md: Document --build-arg without value This use case is currently _working correctly_, which is nice, but there is no documentation to be found about it. This PR fixes that. Signed-off-by: Per Lundberg --- docs/reference/commandline/build.md | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/docs/reference/commandline/build.md b/docs/reference/commandline/build.md index 01ab913eca..0c1c491d33 100644 --- a/docs/reference/commandline/build.md +++ b/docs/reference/commandline/build.md @@ -425,6 +425,18 @@ Dockerfile are echoed during the build process. For detailed information on using `ARG` and `ENV` instructions, see the [Dockerfile reference](../builder.md). +You may also use the `--build-arg` flag without a value, in which case the value +from the local environment will be propagated into the Docker container being +built: + +```bash +$ export HTTP_PROXY=http://10.20.30.2:1234 +$ docker build --build-arg HTTP_PROXY . +``` + +This is similar to how `docker run -e` works. Refer to the [`docker run` documentation](https://docs.docker.com/engine/reference/commandline/run/#set-environment-variables--e---env---env-file) +for more information. + ### Optional security options (--security-opt) This flag is only supported on a daemon running on Windows, and only supports @@ -504,7 +516,7 @@ section in the userguide for more information. The `--squash` option has a number of known limitations: -- When squashing layers, the resulting image cannot take advantage of layer +- When squashing layers, the resulting image cannot take advantage of layer sharing with other images, and may use significantly more space. Sharing the base image is still supported. - When using this option you may see significantly more space used due to @@ -581,7 +593,7 @@ $ docker build --squash -t test . If everything is right, the history will look like this: ```bash -$ docker history test +$ docker history test IMAGE CREATED CREATED BY SIZE COMMENT 4e10cb5b4cac 3 seconds ago 12 B merge sha256:88a7b0112a41826885df0e7072698006ee8f621c6ab99fca7fe9151d7b599702 to sha256:47bcc53f74dc94b1920f0b34f6036096526296767650f223433fe65c35f149eb