[mythtv-users] Slave Backend Configuration obscure

Nick knowledgejunkie at gmail.com
Fri Dec 9 02:59:07 EST 2005

On 09/12/05, John Andersen <jsamyth at gmail.com> wrote:
> I have my Master Backend & Frontend working quite nicely with .18.1 and
>  wanted to add another machine.  This second machine works fine as
>  a remote frontend.
>  But I wanted to slap another tuner in this remote machine and use it
>  also as a slave backend (I'd put both cards in the Master If I had
>  the slots).
>  Problem is, with that backend running, there seems to be a problem
>  with ring buffers:
>  2005-12-08 00:00:07.405 RemoteFile::Read() failed in
> RingBuffer::safe_read().
>  2005-12-08 00:00:07.621 RemoteFile::Read() failed in
> RingBuffer::safe_read().
>  2005-12-08 00:00:07.837 RemoteFile::Read() failed in
> RingBuffer::safe_read().
>  2005-12-08 00:00:08.053 RemoteFile::Read() failed in
> RingBuffer::safe_read().
>  Couldn't read file: rbuf://
>  2005-12-08 00:00:08.084 LiveTV not successfully started
>  Just shutting down the slave backend cures the problem.

Does the new slave backend have access to its own
ringbuffer/recordings directories?

>  Is there anywhere written a more complete description of which
> configuration items are done in which machine's setup?  The main Myth docs seem to
>  breeze over this bit.

Not really apart from on the list archive

Once you have a master backend up running successfully with properly
defined video sources (all video sources should be defined on the
master backend), on the slave backend you should ideally:

i) install any new capture cards and ensure they are working normally
outside of MythTV
ii) run mythtvsetup on the slave, and add the new capture cards
iii) setup input connections to connect the video sources (defined on
the MBE machine) to the inputs available on your new capture cards (on
the SBE machine)
iv) ensure the local recordings and LiveTV ringbuffer storage
locations are rw for the SBE backend process user
v) save settings, run the SBE mythbackend process, and check the SBE
logfile for any other problems.
vi) configure the frontend on the SBE machine and enjoy

>  Where do ringbuffers reside when there are two backends? locally
>  on each machine, or on the master only?

Each machine will typically have its own ringbuffer file, which needs
to be accessible to the machine using it. MythTV provides access to
other backend and frontend machines internally through the Myth
protocol so that you can watch TV on a frontend machine using the
capture facility of another machine transparently.

>  How do you keep ring buffers from getting in collision if they are
>  all on the Master?

See above answer. If using a single point of storage such as NFS, I am
not sure, but I would anticipate that each backend is aware of the
existence of other ringbuffer files, otherwise just use a different
directory for the LiveTV buffer for each backend machine on a shared
storage box. A shared recordings directory should not be a problem.


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