[solved] duplicating grub on another hdd

[nordic bro]

I have grub in sda mbr. I want to duplicate sda:/boot to my backup sdc so that if/when sda fails, I can more or less switch over to booting/running my system from sdc.

I suspect all I need to do is "grub-install /dev/sdc" to get grub loaded into sdc's mbr? but then this will update files in sda:/boot/grub correct? would doing "grub-install /dev/sdc" in any way interfere with continuing to use sda for booting/running my system? I wanted to check before I royally mess something up like unknowingly transferring grub from sda to sdc

thanks.

[eccerr0r]

normally I mount the disk that I want to install grub on, and use --root-directory=/that/mountpoint to make sure a copy of the second stage loader gets put on the right device...
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Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
What am I supposed watching?