add next steps to 'README.install'.

README.install

@@ -5,20 +5,75 @@
 # see also:
 #  https://github.com/discourse/discourse/blob/main/docs/INSTALL-cloud.md
 
+# Before you start
+#
+#     1.  Preparing your domain name
+#     2.  Setting up email
+
 # Installation
 #
-#     1. Create new cloud server
+#     3.  Create new cloud server
-#     2. Access new cloud server
+#     4.  Access new cloud server
-#     3. Install Prerequisites for Docker
+#     5.  Install Prerequisites for Docker
-#     4. Install Discourse
+#     6.  Install Discourse
-#     5. Edit Discourse configuration
+#     7.  Edit Discourse configuration
-#     6. Start Discourse
+#     8.  Start Discourse
-#     7. Register new account and become admin
+#     9.  Register new account and become admin
-#     8. Post-install maintenance
+#     10. Post-install maintenance
-#     9. (Optional) Add more Discourse features
+#     11. (Optional) Add more Discourse features
 
 
 # ...
 
 
-# 4. Install Discourse
+# ---
+# 5. Install Prerequisites for Docker
+# ---
+
+# Set up and install Docker Engine from Docker's apt repository.
+#
+# see also:
+#    https://docs.docker.com/engine/install/debian/
+#
+# Add Docker's official GPG key:
+#
+apt-get install ca-certificates curl gnupg
+install -m 0755 -d /etc/apt/keyrings
+curl -fsSL https://download.docker.com/linux/debian/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
+chmod a+r /etc/apt/keyrings/docker.gpg
+
+
+# Add the repository to Apt sources:
+#
+echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/debian \
+  $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | \
+  tee /etc/apt/sources.list.d/docker.list > /dev/null
+apt-get update
+
+
+# Install the (latest) Docker packages.
+#
+# apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
+#
+apt install docker-ce
+
+
+# ----------
+#
+# Install a specific version of Docker Engine
+#
+# Start by listing the available versions in the repository:
+#
+#     # List the available versions:
+#     $ apt-cache madison docker-ce | awk '{ print $3 }'
+#
+#     5:24.0.0-1~debian.11~bullseye
+#     5:23.0.6-1~debian.11~bullseye
+#     ...
+#
+# Select the desired version and install:
+#
+#     $ ERSION_STRING=5:24.0.0-1~debian.12~bookworm
+#     # apt-get install docker-ce=$VERSION_STRING docker-ce-cli=$VERSION_STRING containerd.io docker-buildx-plugin docker-compose-plugin
+#
+# ----------