Update README.md

docker/README.md

@@ -1,16 +1,16 @@
 ## Use An Existing 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:latest`.
-- Run this image in a container: `docker run -it shaomeng/sperr-docker:latest`
+- 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:latest`
+  `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:latest`.
+- Give an existing image a new tag: `docker tag <image-sha256> sperr-docker:<new-tag>`.