My New iMac Setup Troubleshooting

After 8 years hardworking, the old iMac quit on me eventually. Instead of troubleshooting, I chose to upgrade to a new iMac. Of course, I already have TimeMachine backup on NAS disk. Hope the migration experience would be easy as clicking few buttons. But it wasn’t. At some point, I was so stressed out, almost gave up and decided to return the purchase to get another one. However, as a troubleshooting guy, I eventually came through and get my new iMac up running with all my documents and apps back.


What I need to do, is to setup the new iMac 2017 and migrate my 8 years work out of the old iMac 2010. I have TimeMachine backup on NAS. The disk was about 300GB in size.

The Game Plan

Mac OS is easy to use. With TimeMachine backup, my plan is straight forward:

  • Setup new iMac
  • Transfer everything from old iMac using Migration Assistant

The Problem

(If you don’t want to read the story, please jump to the end of this section.)

The problem was created during the migration process. Although I did some research and knew it might take long time to finish. But what I didn’t know, maybe you should take a note, was how long it should take. For my configuration, the Migration Assistant uses wireless network and ignore my Ethernet connection. (Or maybe there is but I didn’t figure it out). So if you have the latest wireless network at home with blazing fast connection speed, the whole process should take less time. Otherwise, the migration will be extremely slow.

About 2 hours into the migration process, I long-pressed the power button because the process was still on “estimating size of the files”. At that moment, I didn’t know how long I should wait and thought the process was frozen, so I powered off the machine, which was my first mistake. After turned it back on, I made the second mistake, to restore the new iMac from TimeMachine backup. After 9 hours restoration, the process was finished without any warning or error. But when the machine was powered back on, it couldn’t pass the startup. The iMac went into an infinite reboot loop. It rebooted itself again and again after progress bar went to about 50 – 60%. Obviously, there was something not done right.

To get myself out of the trouble, my solution was to wipe the disk and do a clean installation, following by another migration attempt. But I then ran into few other issues:

  • I couldn’t re-install OS because the hard disk was locked.
  • “Erase partition” stuck at “Deleting Volume …”, it took over 1 hour before I terminated the process. (To understand how long it should take to erase partition, I did a test on my MacBook Pro. The process should take less than few seconds)
  • I got luck to get an unlocked system disk even after I terminated the “Erase partition” immaturely, (I had no clue how I did and why that happened), and the OS installation was a success. But the iMac went back into the constant reboot loop again. At certain point of the reboot, I even saw hardware issue message few times.

After two discussions with Apple Technical Support, I prepared to bring the new iMac back to Apple Store. If I couldn’t get it fixed immediately at Apple Store, my plan was to return the purchase and get another. I had been without a working iMac for 7 days and job piled up quickly. It was a torture.

To sum up, here is my experience:

  • 2 hours Migration Assistant, terminated immaturely.
  • Restore from TimeMachine backup, couldn’t boot up.
  • Re-installation of Mac OS didn’t work, same reboot loop issue.

The Solution

As a technical person who loves troubleshooting, it kills me to give up without seeing myself making all the effort I can to resolve any issue. There was one word from Apple Technical Support encouraged me to give it another try to resolve the problem myself. I was told that “this should be a software problem.”, even though I saw a hardware error message. This means, it is resolvable. I just didn’t find the real issue.

Since this is an iMac mid-2017 with a fusion drive, I started my research on fusion drive as I don’t have any experience with this kind of setup. After reading few posts, I got a strong feeling that, there should be an issue with the fusion drive setup. I need to fix it in Terminal – the Command Line. Especially when I run this command and didn’t get the right result:

The command is:

diskutil cs list

The command is to show all CoreStorage volumes. What I get was

No CoreStorage logical volume groups found

At that moment, I believed I found the issue, the iMac had a fusion drive configuration issue and I should rebuild it. The issue should be introduced by my interruption during the previous unsuccessful setup attempts. The solution can be found here:

How to fix a split Fusion Drive

After successful rebuilding fusion drive, I reinstalled Mac OS. You know what happened next. I backup the iMac using an external disk and then started migration process. With previous experience, I waited patiently.