I did not have the TS-752 and wanted to boot from the SD card.

1. Ordered List ItemPlug the TS-7500 to a Ethernet port
2. Power it up
3. Telnet to it (default address: 192.168.0.50)
4. Type:

   cd /
   
   rm linuxrc
   
   ln -sf /linuxrc-sdroot /linuxrc 
   
   save

5. Open up this file

   vi linuxrc-sdroot

   and comment out these lines if they exist (otherwise don't modify anything):

   #if [ "$bootdev" == "0x1" ]; then
      mount -oro /dev/nbd9 /mnt/root
   #fi

6. Reboot!