SD card back up

[mikenkc]

I went to back my Pi3 OS today and when asked to choose which drive to read from I get Recovery(D) or boot (F) to pick. Which one do I used use or do I use both?

[jnealand]

If it was me I would just build a second SD card, test it and put it aside.  Having a second card lets you just power off, swap cards, power up.  All your data and config info is on the USB drive.  If you have multiple Pis, having a backup SD lets you have a card that works with all your Pis.  The key thing to backup is your USB files in my mind.

I have swapped cards many times with no problems so I know it works.