update README

README.md

@@ -25,8 +25,7 @@ The name of SPERR stands for **SP**eck with **ERR**or bounding.
 SPERR documentation is hosted on Github [Wiki](https://github.com/NCAR/SPERR/wiki) pages. To get started, one might want to
 [build SPERR from source](https://github.com/NCAR/SPERR/wiki/Build-SPERR-From-Source) and explore compression and decompression
 utilities for [3D and 2D](https://github.com/NCAR/SPERR/wiki/CLI%3A-3D-and-2D-Compression-and-Decompression-Utilities) inputs.
-One may also want to pull a [docker image](https://hub.docker.com/r/shaomeng/sperr-docker)
-which contains SPERR in a complete development environment, or use [spack](https://spack.io/) to install SPERR by one command `spack install sperr`.
+One can also use [spack](https://spack.io/) to install SPERR by a single command `spack install sperr`.
 Finally, a collection of canonical scientific data sets is available at [SDRBench](https://sdrbench.github.io/) for testing and evaluation purposes.
 
 SPERR also provides programming [API in C++ and C](https://github.com/NCAR/SPERR/wiki#sperr-c-api).

docker/README.md

@@ -1,16 +1,15 @@
-## Use An Existing Image
+## Build Your Own Image
+
+A `Dockerfile` is located [here](https://github.com/NCAR/SPERR/tree/main/docker) so you can build your own SPERR images.
+- Build an image: enter the same folder with `Dockerfile`, and then type `docker build -t sperr-docker:tag1 .`.
+- Give an existing image a new tag: `docker tag <image-sha256> sperr-docker:<new-tag>`.
+
+## Use An Image
 
-- One can pull a docker image with SPERR inside from [Docker Hub](https://hub.docker.com/r/shaomeng/sperr-docker): `docker pull shaomeng/sperr-docker:<tag-name>`.
 - Run this image in a container: `docker run -it shaomeng/sperr-docker:<tag-name>`
 - Inside of this container is a complete development environment. SPERR source code is located at `/home/Odie/SPERR-src` and SPERR is compiled at `/home/Odie/SPERR-src/build`.
 - In the build directory, one can run the unit tests (`ctest .`) to verify that the executable works.
 - One can also mount a directory from the host system to the container so SPERR can operate on real data:
  `docker run -it --mount type=bind,source=/absolute/path/to/host/directory,target=/data,readonly shaomeng/sperr-docker:<tag-name>`
 
-## Build Your Own Image
-
-A `Dockerfile` is located [here](https://github.com/NCAR/SPERR/tree/main/docker) so you can build your own SPERR images.
-- Build an image: enter the same folder with `Dockerfile`, and then type `docker build -t sperr-docker:tag1 .`.
-- Give an existing image a new tag: `docker tag <image-sha256> sperr-docker:<new-tag>`.
-