docs: add shared build requisites guide

build/BUILD_REQUISITES.md

@@ -0,0 +1,103 @@
+# Build Requisites
+
+## Introduction
+
+To simplify Euro-Office Document Server builds, this project uses Docker under the hood.
+You will find instructions below to prepare your build user to run Docker correctly.
+This setup is usually done only once per machine.
+
+These Docker instructions are focused on Ubuntu. If you use another OS or distro,
+follow the equivalent Docker CE installation steps for your platform.
+
+Be aware of RHEL 8 based distributions. Look for a docker-ce how-to. Installing
+the default `docker` package may install `podman` and `buildah`, which do not fully
+behave like Docker CE for this workflow.
+
+## Choose a build user
+
+Builds should run with a regular user, not with `root`. That user must be a member
+of the `docker` group.
+
+This documentation uses `eobuilder` as an example build user.
+
+Note for advanced users: if you must use `root` for Docker execution, review the
+Dockerfiles used in this project and adjust your setup accordingly.
+
+## Docker setup
+
+Note: run these commands as `root` or as a user with `sudo` privileges.
+
+### Install Docker prerequisites
+
+```sh
+sudo apt-get update
+sudo apt-get remove docker docker-engine docker.io
+sudo apt-get install linux-image-extra-$(uname -r) linux-image-extra-virtual
+sudo apt-get install apt-transport-https ca-certificates curl software-properties-common
+```
+
+### Set up Docker apt repository
+
+```sh
+curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
+
+sudo tee /etc/apt/sources.list.d/docker.list <<EOM
+deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable
+EOM
+
+sudo apt-get update
+```
+
+### Install Docker
+
+```sh
+sudo apt-get install docker-ce
+```
+
+## Docker user - Add to group
+
+```sh
+sudo usermod -a -G docker eobuilder
+```
+
+## Docker user - Re-login
+
+To use Docker correctly from the `eobuilder` user, log out and log back in after
+adding the user to the `docker` group.
+
+## Docker user - Hello world
+
+Run Docker's standard hello-world example as `eobuilder`.
+
+If hello-world does not work, builds based on this project's Dockerfiles will not
+work either.
+
+## Docker driver setup
+
+Create and select a Buildx container driver, then bootstrap it:
+
+```sh
+docker buildx create \
+  --name container-builder \
+  --driver docker-container \
+  --use
+
+docker buildx inspect --bootstrap
+```
+
+## Git SSH keys
+
+Note: run these commands as the `eobuilder` user.
+
+Create an SSH key:
+
+```sh
+ssh-keygen -t rsa -b 4096 -C "eobuilder@domain.com"
+```
+
+Use the email address associated with your GitHub account.
+
+Then upload your public key (`~/.ssh/id_rsa.pub`) to your GitHub profile:
+https://github.com/settings/keys
+
+If needed, you can use a dedicated GitHub account for build automation.

build/README.md

@@ -2,6 +2,8 @@
 
 Docker image where we are experimenting with building the Euro-Office Document Server.
 
+Before starting, make sure Docker and your build user are set up: [Build Requisites](./BUILD_REQUISITES.md).
+
 ## Building the Image
 
 First, clone the repositories for the core-fonts, sdkjs, web-apps, and server components:

develop/README.md

@@ -3,6 +3,8 @@
 
 The docker compose environment in this directory allows to run document server built from our code base. It runs a container called develop, which just adds the development (i.e., build) tooling to the finalubuntu container. This lets you build pieces on the fly directly inside the container, saving build time when developing:
 
+Before starting, make sure Docker and your build user are set up: [Build Requisites](../build/BUILD_REQUISITES.md).
+
 - Clone the Euro-Office Nextcloud connector as a sibling of `DocumentServer` (i.e. inside the same `euro-office-public` parent):
   ```sh
   git clone https://github.com/Euro-Office/eurooffice-nextcloud.git ../../eurooffice-nextcloud