README: Add update notes.

with `carton exec hypnotoad index.pl`.

Note that you should provide imprint and privacy policy pages. Depending on

traffic volume, you may also want to increase the amount of worker processes.

See the Setup notes below.

traffic volume, you may also want to increase the amount of worker processes

and install a caching proxy in front of DBF.  See the Setup notes below.

To update your DBF installation, run `git pull`, ensure that all files are

readable by your www user, and re-run `carton install` or `cpanm --installdeps

.`.

Installation with Docker

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Use `docker run -e DBFAKEDISPLAY_WORKERS=4 ...` and similar to pass environment

variables to the db-infoscreen service.

To update your Docker installation, fetch a new image from Docker Hub and

re-start the container.

Setup

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DBF will periodically reload `share/zugbildungsplan.json`. You can use your

service supervisor (e.g. `systemctl reload db-infoscreen`) to force an

immediate reload. You may also ignore the file entirely; it is entirely

optional.

immediate reload. You may also ignore the file; it is entirely optional.

System requirements

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