SmartStor telnet access solution previously described here is fine, but has one significant problem: configuration settings does not persist after reboot, because /etc is mounted as a ramdisk and its contents (mostly) populated using startup system scripts.
Instead of modifying and reflashing system software it's much easier to create simple application plugin (idea borrowed from this post and telnet access plugin description in the same thread).
The plugin does very few things:
- suppresses automatic rewriting of /etc/telnet.user
- enables telnet access for 'admin' user
- adds 'admin' to /etc/sudoers
After all, plugin modifies AFPD configuration for better Apple Time Machine compatibility.
You may download it from here and install using PASM or SmartNAVI (disclaimer: I take no responsibility for any possible data damage, lost warranty or other issues caused by usage of this plugin).