From 98279e52b37e9ad07a460686b2c9c3bfbd7dcaa1 Mon Sep 17 00:00:00 2001
From: Georg Lauterbach <44545919+georglauterbach@users.noreply.github.com>
Date: Wed, 28 Sep 2022 09:25:07 +0200
Subject: [PATCH] docs: add note about Docker version when building (#2799)

* add note about Docker version when building
* add note about `DOCKER_BUILDKIT` and build arguments
* provide link to COPY command
---
 .../examples/tutorials/docker-build.md        | 26 ++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/docs/content/examples/tutorials/docker-build.md b/docs/content/examples/tutorials/docker-build.md
index d88cb221..98f19be9 100644
--- a/docs/content/examples/tutorials/docker-build.md
+++ b/docs/content/examples/tutorials/docker-build.md
@@ -4,6 +4,8 @@ title: 'Tutorials | Docker Build'
 
 ## Building your own Docker image
 
+### Submodules
+
 You'll need to retrieve the git submodules prior to building your own Docker image. From within your copy of the git repo run the following to retrieve the submodules and build the Docker image:
 
 ```sh
@@ -12,11 +14,33 @@ docker build -t mailserver/docker-mailserver .
 ```
 
 Or, you can clone and retrieve the submodules in one command:
+
 ```sh
 git clone --recurse-submodules https://github.com/docker-mailserver/docker-mailserver
 ```
 
 Retrieving the git submodules will fix the error:
-```
+
+```txt
 COPY failed: file not found in build context or excluded by .dockerignore: stat target/docker-configomat/configomat.sh: file does not exist
 ```
+
+### About Docker
+
+#### Version
+
+We make use of build-features that require a recent version of Docker. Depending on your distribution, please have a look at [the official installation documentation for Docker](https://docs.docker.com/engine/install/) to get the latest version. Otherwise, you may encounter issues, for example with the `--link` flag for a [`#!dockerfile COPY`](https://docs.docker.com/engine/reference/builder/#copy) command.
+
+#### Environment
+
+If you are not using `make` to build the image, note that you will need to provide `DOCKER_BUILDKIT=1` to the `docker build` command for the build to succeed.
+
+#### Build Arguments
+
+The `Dockerfile` takes additional, so-called build arguments. These are
+
+1. `VCS_VERSION`: the image version (default = edge)
+2. `VCS_REVISION`: the image revision (default = unknown)
+
+When using `make` to build the image, these are filled with proper values. You can build the image without supplying these arguments just fine though.
+