Start upon existence of multiple devices

[Jan Ceuleers]

Hi.

I have a howto question. If there is somewhere else more appropriate to 
such questions then feel free to point me there.

I have a task that should not be started until multiple devices have 
been registered. In the general case the order in which these devices 
come up after boot is unknown and may differ from one boot to the next 
(e.g. depending on whether the devices have retained their firmware).

The specific use cases I have in mind are the following:

1. The MythTV master backend process should not be started until 
networking is up, and the mysql server is up, and all configured video 
capture devices are ready for use.

2. The MythTV slave backend process should not be started until 
networking is up and all configured video capture devices are ready for use.

So there are multiple problems:

A. The problem pointed out above with regard to a dependency on multiple 
devices;

B. The fact that, at the moment, the /etc/init/mythtv-backend.conf file 
is generic rather than taking the above dependencies into account, 
knowing that they differ depending on the use case and available video 
capture devices. So ideally a way is needed to automatically generate 
the .conf file.

Thanks, Jan