On Sat, Nov 23, 2019 at 7:15 PM sebb <seb...@gmail.com> wrote: > > The Puppet init.pp script [1] sets up several directories which are not yet > reflected in the Docker build, e.g. /srv/cache > > Where is the best place to set these up?
Short answer: in the Dockerfile. Longer answer: 1) Anything that is static and idempotent can and should be build in the Dockerfile. The theory is that you should be able to destroy a container and rebuild it from the Dockerfile and end up with exactly the same image. In practice this isn't exactly true (apt-get update may get newer versions of packages, for example), but is close enough to be true in practice. One thing that a Dockerfile can NOT depend on is mounted file systems or environment variables. docker-compose.yaml can make use of environment variables. 2) Anything that is in the container (e.g.. changes made by commands invoked via RUN or EXEC) should be ephemeral. If a container is pruned, there should not be anything lost of significance. 3) Everything else should go into a volume as volumes have lives outside of images and containers. Host volumes are mounted, and on macOS and Windows have performance characteristics of a remote file system (e.g. nfs) whereas on Linux they have native mounted performace. Anonymous and named volumes have native performance on all operating systems, but can't be directly accessed by the host machine. Notes: 1) During development, the contents of the local clone of whimsy and even the gems installed are generally not considered static, and hence belong on a volume. 2) The current docker:entrypoint rake task contains only commands that can be run fast and depend on things like contents of volume mounts (e.g. the whimsy source code) or environment variables (the name of the user's home directory). - Sam Ruby > [1] > https://github.com/apache/infrastructure-puppet/blob/deployment/modules/whimsy_server/manifests/init.pp#L178
