I can confirm that this does work with my NI RT Linux based cDAQ-9134.
Boot into safe mode:
/etc/init.d/nisetbootmode force-safemode && reboot
*note that it seems rebooting while in safe mode will boot back into run mode (unless you have some critical error preventing it, in which case it will fail back into safe mode)
Boot into run mode (Redundant, see comment above):
/etc/init.d/nisetbootmode force-normal && reboot
It's important to note that the booting in/out of safe mode is done differently for the Intel x64 (i.e. Atom) based products like the cDAQ 9134 vs. the Phar Lap and ARM Processors (like cRIO 9068).