[mythtv-users] SSH from the Backend

[John]

I am trying to issue a command from the master to the slave backend 
using ssh.

Something like "ssh 'pi at 192.168.0.127' 'sudo pistop.sh'"

It works from the user account but not when called from the master 
backend presumably because it runs under account 'mythtv'.

How do I give the 'mythtv' account ssh credentials?