This testvar must be explicitly defined in the configuration file
The tr69DUInstallImage is the full path name to a Deployment Unit file on the CDRouter Linux host that should be used for the DU install tests in the od128.tcl test module. The full path to the file must be used.
Whern this testvar is set, the tr69DUInstallUUID and tr69DUChangeExecEnvRef testvars must also be set.
For large firmware files, the tr69DUChangeTimeout value should be increased.