I want to save the DMG on an external harddrive. Would it interfere with anything currently on my external harddrive?
No. It's just a file.
Where does TM come into play? If your external drive is your TM drive, you can still use the drive for other files. They will just reduce the amount of space TM has for backup, and thus how far back in time it will go.
Thank for your O. Now if I opt to do a clean install, can I do a clean install from the DMG that will be saved to the external harddrive after I wipe my mac's disk clean a reformat it?
I think I was adding to my post while you posted this one. You'll find the answer there. I haven't actually booted to the DMG, so I don't know exactly what the option looks like. But, I believe it is called "Clean Install".
Making bootable Lion installs is on my todo list. I'll probably make a partition on one of my externals and also on a USB flash drive.
But what im trying to find out is if I make a partition in my external harddrive and save Lion DMG on there, can I Clean Install from the external Harddrive on to my iMac's harddrive (of course it will be wiped clean).
I think you have the right idea, but I think I need to clarify where you say "save Lion DMG". You can't just copy the DMG file to the partition. You have to restore the contents to the partition. This is done using Disk Utility's Restore function.
Run Disk Utility. Select your new partition from the list on the left, then select the Restore tab. Drag the DMG to the "source" (or use the "Image..." button to find the file). Now, drag the new partition from the list to "destination". Double (or triple) check that you have the proper destination set (Restore WILL erase the destination partition), then click Restore. You'll be prompted to make sure you are telling it to do what you want it to do.
Once the Restore is complete, you should be able to restart while holding down the "opt" key and select the volume from the list.
From there, you should be able to do the Clean Install. Since, as I mentioned, I haven't booted from the DMG yet myself, I can't say exactly what you'll see. But, you should have access to Disk Utility to erase the target drive and/or have the option to do so when you start the Clean Install.
I'm just going on past experience with other OS-X installs - which, up until now, have always been done from a separate, bootable device/partition. I hate to post directions unless I have exactly the correct naming, menu, button, etc. (I still have Disk Utility in front of me for reference while I posted the above, even though I've done the process a gazillion times myself.) So, if someone here who's done this with Lion can post the specifics, I'm sure the OP would appreciate it.
After you purchase Lion and download it, but before you install (the installer deletes itself upon completion of Lion install), copy the installer app (in your app folder) to your external HD. Follow directions here and elsewhere on how to get the DMG out of the installer (it sounded like you already had or knew how, since you were discussing the DMG.
"Restore" is the term used by Disk Utility to image/clone one volume (partition) to another. When you Restore the DMG, you are telling Disk Utility to make an exact copy of its contents to the destination partition.
If you need help setting up a new partition on your external, please search MR for the procedures; if it's still not clear, I'd be happy to help with that.
I can't think of a reason it would have 6GB of data in it after creating the new partition. There are some files that are always there after creation, though it's in the MB range.
Try resizing the partition, either by dragging the frame smaller or by entering the new size (old size - 8GB). I'd suggest the latter, because dragging has trouble with small sizes. After entering the new size, Apply. You should now have free space between the "new iMac" partition and the old.
Now, try and select the free space and see if it will let you create a new partition there. Don't use the "+".
% [B]diskutil list[/B]
% [B]gpt show -l disk1[/B]