From 42263dafcf05dc598fd98d1b9dd098acb09a4e72 Mon Sep 17 00:00:00 2001 From: Charles Chan Date: Sat, 18 Jul 2015 21:09:48 -0700 Subject: [PATCH] Minor edits to Environment variables section * Clarify the list of supported instructions. * Clarify behavior of ONBUILD, based on comments by @SvenDowideit, @theJeztah in PR #14735. * Reorder list of instructions in alphabetical order. Signed-off-by: Charles Chan --- docs/reference/builder.md | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/docs/reference/builder.md b/docs/reference/builder.md index 93355fa3bf..9fe3a740fc 100644 --- a/docs/reference/builder.md +++ b/docs/reference/builder.md @@ -152,18 +152,24 @@ Example (parsed representation is displayed after the `#`): ADD . $foo # ADD . /bar COPY \$foo /quux # COPY $foo /quux -The instructions that handle environment variables in the `Dockerfile` are: +Environment variables are supported by the following list of instructions in +the `Dockerfile`: -* `ENV` * `ADD` * `COPY` -* `WORKDIR` +* `ENV` * `EXPOSE` -* `VOLUME` * `USER` +* `WORKDIR` +* `VOLUME` -`ONBUILD` instructions are **NOT** supported for environment replacement, even -the instructions above. +as well as: + +* `ONBUILD` (when combined with one of the supported instructions above) + +> **Note**: +> prior to 1.4, `ONBUILD` instructions did **NOT** support environment +> variable, even when combined with any of the instructions listed above. Environment variable substitution will use the same value for each variable throughout the entire command. In other words, in this example: