How to monitor hard disks on Raspberry

Hello guys.
I’ve been monitoring my Micro SD (64GB) for years, but now I also have an SSD (120GB) hooked to my Raspberry pi.
I really don’t know how to get the entity “disk_free”.

Can u guys help me?

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Maybe of interest, someone already did al the work :wink: I’m using this and satisfied…

you didn´t get it. I do monitor my Rpi, as you can see the screenshot…I just want to know how to see 2 different Hds… I´m doing something wrong with the “arg” line probably…