Docker Fixes

Dockerfile

@@ -20,14 +20,6 @@ ENV DEBIAN_FRONTEND noninteractive
 # ShellCheck version
 ENV SHELLCHECK_VERSION=0.7.0
 
-# Pick a Ubuntu apt mirror site for better speed
-# ref: https://launchpad.net/ubuntu/+archivemirrors
-ENV UBUNTU_APT_SITE ubuntu.cs.utah.edu
-
-# Replace origin apt package site with the mirror site
-RUN sed -E -i "s/([a-z]+.)?archive.ubuntu.com/$UBUNTU_APT_SITE/g" /etc/apt/sources.list
-RUN sed -i "s/security.ubuntu.com/$UBUNTU_APT_SITE/g" /etc/apt/sources.list
-
 # Install apt packages
 RUN apt update         && \
     apt upgrade -y -o Dpkg::Options::="--force-confdef" -o Dpkg::Options::="--force-confold"  && \

README.md

@@ -965,35 +965,22 @@ export NVM_DIR="$HOME/.nvm"
 
 ## Docker For Development Environment
 
-To make the development and testing work easier, we have a Dockerfile for development usage, which is based on Ubuntu 18.04 base image, prepared with essential and useful tools for `nvm` development, to build the docker image of the environment, run the docker command at the root of `nvm` repository:
-
-```sh
-$ docker build -t nvm-dev .
-```
-
-This will package your current nvm repository with our pre-defined development environment into a docker image named `nvm-dev`, once it's built with success, validate your image via `docker images`:
-
-```sh
-$ docker images
-
-REPOSITORY         TAG                 IMAGE ID            CREATED             SIZE
-nvm-dev            latest              9ca4c57a97d8        7 days ago          650 MB
-```
-
-If you got no error message, now you can easily involve in:
-
+To make the development and testing work easier, we have a Dockerfile for development usage. This is an Ubuntu 22.04 base image with some development tools added and a copy of this repo (including the current working copy) copied to `~/.nvm/` in the image. To build and use it, `cd` to the root of this repo and:
 ```sh
-$ docker run -h nvm-dev -it nvm-dev
+docker build -t nvm-dev .           # Create the nvm-dev image
+docker images                       # Confirm nvm-dev appears in the list.
 
-nvm@nvm-dev:~/.nvm$
+#   Create a container named `nvm-dev` (with the same hostname)
+#   and enter an interactive session in it.
+docker run --name nvm-dev -h nvm-dev -it nvm-dev
 ```
 
-Please note that it'll take about 8 minutes to build the image and the image size would be about 650MB, so it's not suitable for production usage.
+This will place you in the container in the `~/.nvm/` directory as the `nvm` user. When you exit the container will not be deleted (so as to avoid losing any work in it); you can re-enter the container with `docker start -i nvm-dev` or delete it permanently with `docker container rm -f nvm-dev`. (For more information on using Docker, see the [website][dr-web] and [documentation][dr-docs].
 
-For more information and documentation about docker, please refer to its official website:
+Note that the build takes several minutes and well over half a gigabyte of disk space, so it's not suitable for production usage.
 
-  - https://www.docker.com/
-  - https://docs.docker.com/
+[dr-docs]: https://docs.docker.com/
+[dr-web]: https://www.docker.com/
 
 ## Problems