The terms task directory and allocation directory are used throughout the
documentation but these directories are not the same as the `NOMAD_TASK_DIR`
and `NOMAD_ALLOC_DIR` locations. This is confusing when trying to use the
`template` and `artifact` stanzas, especially when trying to use a destination
outside the Nomad-mounted directories for Docker and similar drivers.
This changeset introduces "allocation working directory" to mean the location
on disk where the various directories and artifacts are staged, and "task
working directory" for the task. Clarify how specific task drivers interact
with the task working directory.
The 'docker.config.infra_image' would default to an amd64 container.
It is possible to reference the correct image for a platform using
the `runtime.GOARCH` variable, eliminating the need to explicitly set
the `infra_image` on non-amd64 platforms.
Also upgrade to Google's pause container version 3.1 from 3.0, which
includes some enhancements around process management.
Fixes#8926
* docker: support group allocated ports
* docker: add new ports driver config to specify which group ports are mapped
* docker: update port mapping docs
> If you do not run Nomad as root, make sure you add the Nomad user to the Docker group so Nomad can communicate with the Docker daemon.
Changing the username in the example from `vagrant` to `nomad`. Vagrant isn't addressed in the entire document, so I guess that this was a mistake.
