1 Tags and digests
Users need to be aware of the meaning of tags when using Docker images repeatedly.
For example, a tag latest used by many images (docker automatically complements latest if the tag is not specified) is generally constantly updated to follow the latest version. The following command will run R 3.6.1 at some point in the past, R 4.2.0 today, and another version of R a year later.
Then, how about the following command then? Since the tags of rocker/r-ver represents the R version, this command will always run R 4.2.0.
However, rocker/r-ver images are periodically rebuilt, so software versions other than R are not fixed (they receive security updates through periodic rebuilds).
If you want to always use the exact same image, you generally need to specify the image with a digest rather than a tag.
docker run --rm -ti rocker/r-ver@sha256:f32b3e9e353fa63092093f2ce590d819f56eac92f6f79e97906d4f2b0eee5ef3Digests can also be used on Dockerfiles.