On single bay My Cloud units running v04.04.01-112 firmware there is an option to shut down the unit via the Dashboard > Settings > Utilities > Device Maintenance > Shutdown. Check to see if there is a similar option with the v2.x firmware.
With the first gen My Cloud units one can also use SSH to issue a shutdown or reboot command. I assume something similar can be done with the second gen units running v2.x firmware. One can use Plink.exe, a part of the Putty program, to send the command. Plink can be downloaded from this link: http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html
Here are the call's I use both in a batch (.bat) file on my computer (that reside in the same directory as Plink) and in SSH Button on my Android phone. Note on the SSH Button app one only uses the actual SSH call like
/sbin/shutdown -h -P now. Obviously replace the IP address correct value for your setup.
Shutdown and power off:
plink.exe -ssh -l root -pw welc0me 192.168.1.10 /sbin/shutdown -h -P now
plink.exe -ssh -l root -pw welc0me 192.168.1.10 /sbin/shutdown -r now
Power off only:
plink.exe -ssh -l root -pw welc0me 192.168.1.10/sbin/poweroff
plink.exe -ssh -l root -pw welc0me 192.168.1.10/sbin/reboot