Yes, you can do so, but you have to log in to S4 via SSH. 

Putty software can be downloaded from their website @  http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html

Modifying the config file value that is not modifiable via the web control panel, may voids the warranty.  Use CAUTION when you modify this setting.

Any file you attempt to make changes, please make a back up file first!!

cp originalfilename originalfilename.copy

then use command such as "vi" to edit the file.  

If something really goes wrong, you can always try to factory reset the S4 by using a paperclip to the bottom hole (left side bottom) next to the LCB screen.  Press and hold the button for at least 5 seconds and let it go.  Then wait for 2 minutes, power it off and power it back on!

If that doesn't work, you can always reimage the default image file from http://www.bitmaintech.com Support Page.


PSA: Tim.Shao19 is from Bitmain Tech