What directories should I backup for my allstar3 node?

[Mason10198]

How do you make an exact duplicate sdcard of my system

I am just learning linux and have a ASL3/Shari node running. I would like to make a duplictae of my sdcard so that if I have any problems or break something, I will be able to just change the sdcard to the backup one and be back in business. I read alot about backps but am even more confused now. My question is, is there and easy way to make an exact duplicate of my sdcard for this purpose? Thanks for any help you might be able to offer. Dave N8EPF