Apple UDIF read-only compressed (zlib) Media

[Ambrosia7177]

What is that???

I am in middle of formatting my new 1TB HGST hard-drive which is in an external USB3.0 case.

In Disk Utility, under "External", I see:

ASMT 2115 Media
1TB Uninitialized

Then under "Disk Images", I see:

Apple UDIF read-only compressed (zlib) Media
9.28GB Disk Image External Physical Disk

And then nested under that I see:

InstallESD
8.94GB Disk Image External Physical Volume Mac OS Extended

What in the world does all of that mean???

 

[Ambrosia7177]

I am wondering if it relates to my download of High Sierra on Monday?

I moved my High Sierra download outside of the Application folder to a personal folder.

Don't want to touch what I described in my OP for fear of breaking something!

 

[Mr_Brightside_@]

That's what it is.

 

[Ben J.]

That's what it is.

What?.

I too have a UDIF disk showing up in Disk Utilities. I too recently downloaded a Mac OS installer from Apple yesterday. (Planning to make a USB installer.) I too copied the Installation file from applications to an external drive and deleted the original. But disk usage is the same. I didn't get the 12 gbs of disk space back.

Now I see in Disk Utilities this 12gb "Apple UDIF read-only" that says it's mounted, but doesn't show in Finder. If I right-click it in DU and select "Show in finder, it opens a window in Finder and I can see the contents of it. But if I command-click on the window title it shows that it's in the top level. And yet there I see only my other physical disks. No UDIF.

So where is the .dmg?
How can I delete it?

 

[Ben J.]

OK. Ejecting the disk in DU, immediately released the 12gb of disk space.
I guess the UDIF volume was mounted from the "Mac OS installer" right after I downloaded it, and stayed active (but invisible) even though I deleted the file from applications folder after having copied it to an external disk.