reproducibility.md

title	Reproducibility
description	Reproducibility of Rocker Containers.

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.

docker run --rm -ti rocker/r-ver:latest

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.

docker run --rm -ti rocker/r-ver: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:f32b3e9e353fa63092093f2ce590d819f56eac92f6f79e97906d4f2b0eee5ef3

Digests can also be used on Dockerfiles.

FROM rocker/r-ver:4.2.0

FROM rocker/r-ver@sha256:f32b3e9e353fa63092093f2ce590d819f56eac92f6f79e97906d4f2b0eee5ef3

:::{.callout-tip}

If a tag and digest are specified at the same time, the digest is used.

FROM rocker/r-ver:latest@sha256:f32b3e9e353fa63092093f2ce590d819f56eac92f6f79e97906d4f2b0eee5ef3

FROM rocker/r-ver:4.2.0@sha256:f32b3e9e353fa63092093f2ce590d819f56eac92f6f79e97906d4f2b0eee5ef3

:::