How to set up an external HDD to back up to Time Machine?

[Macavity224]

I have 2 external HDD's currently. One of them is set up as a time machine, and I use the other one to store files that I don't keep on my computer. Is it possible to set up this external so that it also backs up to my Time Machine drive, or would I have to manually move everything from the external onto my computer, then from there, back it up to the Time Machine?

I'm on Mac OSX 10.7.5 for reference.

Thanks!

 

[ColdCase]

As long as the drives are formatted in some kind of apple format, I think all attached drives (except the TM drive of course) are backed up to your TM drive by default. If you want to exclude a directly attached drive you have to open time machine preferences, options and exclude the drive.

Maybe that was a change for 10.8, I don't recall off hand.

 

[Weaselboy]

I have 2 external HDD's currently. One of them is set up as a time machine, and I use the other one to store files that I don't keep on my computer. Is it possible to set up this external so that it also backs up to my Time Machine drive, or would I have to manually move everything from the external onto my computer, then from there, back it up to the Time Machine?

I'm on Mac OSX 10.7.5 for reference.

Thanks!

Time Machine by default will exclude external drives from backup. Just attached the external you want to backup and go to the Time Machine panel in System Prefs then click the options button and remove the external from the exclusions list. From then on the external will get backed up to the TM backup on your second external drive just like you want.