[mythtv] Running SVN & Stable (18.1) on same network

Michael T. Dean mtdean at thirdcontact.com
Mon Jan 23 07:45:34 UTC 2006

Matthew Drobnak wrote:

>Inspired by a similar thread...
>I have 1 backend running 18.2, one frontend running 18.2 (diskless),
Since there is no official 0.18.2, I'll assume you're referring to 

>and one front/back machine running SVN...Is it possible to set the
>backend @ 18.2 as the master backend, the SVN as a slave backend,
>and view the resulting recordings on the 18.2 frontend?
Actually, you shouldn't run different versions in master/slave 
configurations--locally or networked.  If you have different versions, 
they should never communicate with one another (i.e. they should be two 
completely separate Myth setups).

Running different versions together is basically as bad as running a 
different version frontend and backend on the same machine.  Remember 
that there's only one database for the entire network of Myth boxes, so 
if the database schema version is different between your different 
versions, you can cause serious problems.  Note that 0.18-fixes uses DB 
schema version 1083 and SVN head is currently at 1122--that's a total of 
39 changes to the database /schema/ (adding/removing columns, tables, 
changing column types, etc.).

A good example of why this is a problem is the basename field.  Since 
current SVN doesn't require the old naming scheme for recording 
filenames (i.e. they don't have to be "chanid_starttime_endtime.nuv" but 
instead default to "chanid_starttime" and have either the ".nuv" or 
".mpg" extension, depending on filename, and can be changed to anything 
the user desires with or without the mythrename.pl script), the filename 
must be stored in the database.  Therefore, any Myth version that uses 
DB schema version 1095 or above will write the basename to the 
database.  Versions before that will not.  So, if you record a file with 
a backend running 0.18-fixes and attempt to play it back on a frontend 
running SVN, it won't work (unless you manually update the basename 
column).  Similarly, if you record a file with a backend running SVN, it 
will write the basename--and the filename will use the new default 
syntax--so when you try to play it back on a 0.18.2 frontend, it won't 
be found.

And, this doesn't even get into the issue of Myth protocol version 
(currently 26 as opposed to 15 in 0.18-fixes) changes...

>Another similar question, 18.2 frontend - if I were to add a analog
>capture card to it, can I get the recordings to be stored on the master
>backend somehow? Would a simple NFS mount do?
Yes (bandwidth permitting).  Just specify the NFS mounted directory for 
the recordings directory.  This also has the benefit that the frontend 
will be able to read recordings created on other backends "locally" 
through the NFS mount instead of forcing the backend to stream the 


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