I'm trying to back up a mac for a friend who move and left her 2020 iMac 27 (intel) with me. She is having me send her the data from it and then sell the mac. The 1TB SSD iMac hard drive is in APFS format. I'm backing up to a Seagate (ST2000LX001) FireCuda 2TB Solid State Hybrid Drive in a USB-C external enclosure.

Things I've tried:

  1. Created external drive as APFS and used time machine to back everything up. Tried to open it on an older (2017) mac like her MacBook air that she took with her. I don't see the drive as there at all. It does not mount.
  2. Started over: Created external drive as Mac Journaled Extended and used time machine. Older mac sees/mounts the disk but all the user files are locked (see pic & seem to be empty)
  3. Created external drive as FAT. Used finder to just copy the user directories in /Users one at a time. Takes hours and invariably fails to complete. Some error happens hours into copying and it terminates the copy process with no clue of what got copied and what didn't.

I either wind up with a drive that old macs can't read, a drive that old macs can read but not see anything, or a partial copy.

What I'd really like to do is:

  1. Go into terminal
  2. Sudo to root
  3. issue some command that copies everything to the external drive ignoring errors and does so without carrying over the MacOS authentication scheme.

So I'd just wind up with an external drive full of her and her family's data that they could easily access without having to deal with permissions nonsense.

What is the best way to achieve this?

  • Mac I'm backing up is 2019 Retina 5k 27" running Big Sur
    – fbonds66
    Apr 17 at 17:35
  • missing screenshot ibb.co/HBfPvNL
    – fbonds66
    Apr 17 at 17:38
  • This is an excellent example of an XY problem, you’re asking how to attack only a portion of the larger problem. Who has permission issues and what OS is going to do the reads? I’ll make a general answer, but there’s a lot not clear yet - keep on editing and if possible, use the native image tools for stack exchange. You can’t edit this too many times as we narrow what you need to learn or get for this to work
    – bmike
    Apr 17 at 17:54
  • I disagree with the XY problem comment. I’m perfectly clear what I want to do and why it makes sense to do it. The problem statement details what is immediately available in the MacOS to extract the data to disk and how that doesn’t accomplish my goal.
    – fbonds66
    Apr 18 at 13:50
  • Migration assistant would be an excellent suggestion if you ignore the fact that my friend - as stated - has moved. The two Macs are not in close proximity. I don’t know about your internet connection, but average consumer Upload speeds are generally in the single digit to low double digit Mbps (i.e. - bits not bytes) range. Migrating a couple hundred gigs this way would take years. The rest of the answer seems more commentary than solution.
    – fbonds66
    Apr 18 at 13:50

1 Answer 1


You could boot to recovery and use disk utility or asr to clone the entire drive. That would save you from needing to ship the computer back to where you can work on it directly.

Once you have it or the clone, I think you want export instead of backup. The latter exists to serve the restore process. When you say anyone can read, that implies you need an export that covers android, Linux, windows, Mac, across 10 to 20 years of operating systems.

You won’t go wrong If you set up time machine and let it format the drive on the assumption that to read it you take that drive to any Mac that’s newer to do the read and export if needed to narrow to a non-apple OS. I would not use two macs for this - much simpler to let the Mac with the data manage the backup. Target disk mode and ignore permissions might help, but you’ll back up a ton of data you don’t likely need if you only want documents.

Also, using migration assistant to move the account over also might help you simplify things if you get them both in the same room.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .