How to setup an external USB drive as a storage device?

[BrianDiPalma]

I have limited backup requirements so I thought I could use the hard drive PBS is running on for backups, seems like I can't so I'm trying to setup an external hard drive instead. When I plug it in it shows up as a storage device but I can't initialize it with GPT as that button is disabled. What should I run on the command line to clear down the hard drive and get it ready to act as a backup hard drive?

 

[Dunuin]

I usually use fdisk /dev/yourDisk then "g" to write a new gpt and "w" to write the changes.

 

[Neobin]

so I thought I could use the hard drive PBS is running on for backups, seems like I can't

Why?
A PBS-datastore is nothing more than a directory. As long as you have a (linux-supported) filesystem and can create a directory, you should be able to use this directory (dedicated) for your PBS-datastore.