Richard,
This is pretty general question whether you can add a component to a post-FBA image.
The answer is totally dependant on "weight" of the component. In other words, how many registry entries and files this component
includes and, sometimes more important, what component's dependencies you have got in your already built and possibly deployed
image.
To grab the Telnet Server component registry and files won't be a big task, especially if you register TlntSvr service and TlntSvr
out-of-process server DCOM object manually.
However, the Telnet Server depends on quite a lot of components (API kernel, api advanced, network and OLE/COM related) so if those
are not in your current image it may become too laborious to add the server properly postFBA. So the first thing you should do is to
explore the dependencies of the Telnet Server component for the purposes of checking their presence in your current image.
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Regards,
KM