Deal with a range of system environment problems by docker and make it deploy easier (#1021)

* Deal with a range of system environment problems by docker and make it deploy easier

---------

Author: garysdevil

README.md

@@ -24,6 +24,8 @@ To build the site, you need to go through a one-time installation
 procedure that takes 15 to 30 minutes.  After that you can build the
 site an unlimited number of times with no extra work.
 
+**[You also can choose to build the site locally by docker, click here to get a guide.](./docker.md)**
+
 ##### Install The Dependencies
 
 **Install RVM**

docker.md

@@ -0,0 +1,63 @@
+[TOC]
+
+- Ensure Docker is installed and running (https://docs.docker.com/desktop/)
+
+## Building The Site Locally By Docker
+
+1. Define the absolute parent path of repository bitcoinops.github.io .
+    ```bash
+    repath=~/Desktop/
+    ```
+
+2. Create the parent folder and go into the parent folder.
+    ```bash
+    mkdir -p ${repath}
+    cd ${repath}
+    ```
+
+3. Download the repository bitcoinops.github.io .
+    ```bash
+    git clone https://github.com/bitcoinops/bitcoinops.github.io
+    ```
+
+4. Building the site.
+    ```bash
+    # Some of the dependencies can take a long time to install on some systems, so be patient.
+    docker run -d --name bitcoinops -p 4000:4000 -v ${repath}/bitcoinops.github.io:/root/bitcoinops.github.io -w /root/bitcoinops.github.io ruby:2.6.4-stretch /bin/bash -c "bundle install && make preview"
+    ```
+
+5. Output the bitcoinops container log
+    ```bash
+    docker logs -f bitcoinops
+    ```
+
+6. The bitcoinops container prints a log like this if building the site is successful.
+    ```log
+            Server address: http://0.0.0.0:4000/
+        Server running... press ctrl-c to stop.
+    ```
+
+6. Visit URL 127.0.0.1:4000 in your browser to view the site.
+
+7. Edit files and save files, then refresh the site in a browser, the site will show the newest content.
+
+## Basic Docker Command
+```bash
+# list all containers.
+docker ps -a
+
+# list all running containers.
+docker ps
+
+# start a container.
+containername=bitcoinops
+docker start ${containername}
+
+# stop a container.
+containername=bitcoinops
+docker stop ${containername}
+
+# output a container log.
+containername=bitcoinops
+docker logs -f ${containername}
+```