Re: [Qemu-devel] [PATCH v3 3/10] qemu-binfmt-conf.sh: add QEMU_CREDENTIAL and QEMU_PERSISTENT

[Unai Martinez Corral]

2019/3/9 10:42, Laurent Vivier:
> On 06/03/2019 05:46, Unai Martinez-Corral wrote:
> > Allow to set options '--persistent' and/or '--credential' through
> > environment variables. If not defined, defaults are used ('no').
> > Anyway, command-line arguments have priority over environment variables.
>
> Could you explain why we could need to use the env variable instead of
> the command line parameter?
>
> I don't see any use case for that.

The main use case is to provide defaults when this script is included
in a docker container. There are three actors involved:

- Developers of QEMU providing some defaults in the script.
- Developer of a docker image including the script from upstream but
changing some defaults by setting envvars inside the container.
- User of the container that might want to override the settings
either by setting the envvars or through the command line.

If the entrypoint to the docker image is any script that executes
qemu-binfmt-conf.sh at some point, the user cannot provide options
through the command line. Envvars allow to do so, without requiring
the user to customize the docker image.

Regards,

Unai