Newbie question: Remote Shutdown...

Not sure if this will help, but take a look at the Tamper Data add on within Firefox. This should get you what you need. I have pulled the below from Frontview within RAIDiator 4.1.6. I have NOT tested it by sending a POST back via CURL (I don't have the time) and there's no guarantee it will work in future versions of RAIDiator.

Shutdown & Reboot only:
https://<your address>/get_handler?PAGE=System&OUTER_TAB=tab_shutdown&INNER_TAB=NONE&shutdown_option2=1&command=reboot&OPERATION=set

Shutdown & Turnoff only:
https://<your address>/get_handler?PAGE=System&OUTER_TAB=tab_shutdown&INNER_TAB=NONE&shutdown_option1=1&command=poweroff&OPERATION=set

If you want a Forced filesystem check, add to the URL (don't forget a leading & as it's a new variable):
force_fsck=1

If you want a Quota check, add to the URL (don't forget a leading & as it's a new variable):
force_quotacheck=1

When using the final URL you want in CURL, make sure you POST it as get_handler probably responds differently to GETs and POSTs, as well as ensuring the user credentials are hardcoded in the command line - hope you're ok with the username and password being hardcoded / visible to people.