[mythtv-users] Upgrading from pre-0.22 MythTV versions

[Raymond Wagner]

On 3/29/2012 23:09, f-myth-users at media.mit.edu wrote:
> For some reason, I was assuming that upgrades might happen where a
> frontend (or mythtv-setup) talked to (the wrong) backend and then told
> the (wrong) backend what to do to upgrade the schema, rather than
> using a direct connection to the DB.  In that case, the (wrong)
> backend already knows the password and hence can corrupt the
> production DB.  Is this impossible?

That should not be possible in 0.24 or 0.25.  In 0.24, `mythtv-setup` on 
any machine is allowed to update if authorized by the user through the 
UI, `mythfrontend` is allowed to update only if a certain command line 
flag was passed to it, and `mythbackend` is allowed to update only if it 
is the master backend.  If the master backend is run detached from an 
interactive terminal, the update will be performed automatically.  
Otherwise, the user is asked whether or not to upgrade on the terminal.  
In 0.25, `mythfrontend` is never allowed to update, and all other 
behavior remains the same.

That means there are two potential routes for trouble.  If the user 
installs a second, newer version of MythTV on the master backend, and 
either runs mythbackend from the same user account or the older version 
is still running and passes the database credentials over UPNP, the new 
backend will think it is the master and proceed to update the database.  
If the user installs a newer version of MythTV anywhere on the network, 
and detects the wrong instance of MythTV over UPNP, they could tell 
mythtv-setup to upgrade the wrong database.  In either case, MythTV will 
find somewhere to make a database backup, allowing the mistake to be 
reverted.