How do I ask Time Machine to back up an external hard drive

[Bill!123]

Time Machine is backing up my internal 1Mac hard drive fine to an external drive ("backup ext drive"). I have another external hard drive attached to the Mac that I would also like to back up to the back-up ext drive. I've looked around on Time Machine as best I can but can't find any place that lists drives to be backed up, so I can tell Time Machine to back it up, also.

I have found a list in Time Machine of drives I can back up to. That list shows both external drives. But of course, I want to back this one up, not use it as a back up drive. Should be something simple I'm missing.

I've seen a lot in the forum about issues backing up external ard drives via Airport Express (or Extreme), but though I have Airport Express, both external drives (back up ext drive and the one to be backed up) are directly connected to the iMac, so I'm not trying to use Airport for this.

OS x 10.5.8

Many thanks.

Bill

 

[xlii]

Time machine will back up all connected (and mounted) drives unless you exclude them (under the options menu).
So if you hook your external drive up via firewire or usb and it is mounted... it will be backed up by time machine by default unless you exclude it by adding it to the exclusion list under options.