Setting up new Mac from Time Machine

Here's what you may have to do if you can't get the iMac to boot and reduce it's data size to what the Mini will take.

1 - set up the new Mini with a user account that has the same full name and short name and password.

2 - get the new Mini up and running,

3 - see if you can connect the Time Machine drive to the Mini and access it. If you can proceed with Step 4.

4 - go to the Time Machine menu in the menu bar with the Option key held down and select "Browse Time Machine Backups". (If you can't browse the try holding down the Option key and selecting "Browse Other Backup Discs…"

5 - go into the latest backup, select the contents of the Pictures folder and restore (provided they will fit on the Mini).

6 - once the restoration is complete copy the Pictures folder to your external drive. Note: make sure your Photos library(s) work correctly on the EHD before deleting the contents of the Pictures folder on the Mini. Do not delete the Pictures folder itself.

7 - do the same for the Music folder.

8 - do the same for the Documents folder if you want to put it on the EHD to provide as much free space on your Mini's boot drive.

NOTE 1: it's wise to try to keep a minimum of 80-100 GB of free space on your boot drive to facilitate optimal system and application performance.

NOTE 2: I recommend an SSD external drive as it's is more reliable and faster than a HDD. I also recommend getting it (if you don't already have one) from OWC (MacSales.com). They are considered the premier hardware supplier for Macs.

If budget is a concern the the following setup might be worth considering:

Even though the above may not be as fast as an SSD in its own case it is quite fast: I can open a 56,00 image Photos library in 2 seconds on such a setup. I have several with my Mini.

I hope this helps.

ShoalMan wrote:

Will I have a problem since the Back up is 1TB but the new Mac mini is only 512GB with and external 4TB?

This will only be a problem insofar as you cannot put ten pounds of potatoes in a five pound sack.

And Migration Assistant will not move data from the TM backup drive to an external drive on the new Mac.

While the TM drive may be 1TB in capacity and full, that doesn't mean that all of that is current files. If you've been using TM for a while, it has been incrementally adding backups to the drive. The size of your full load of files may be something much less than 1TB. But that's neither here nor there.

In my experience, your best course of action would be to buy a new Mac with at least 1TB of internal storage. Don't start your journey from a position behind the 8 ball. 512GB may sound sufficient, but in my experience it hasn't been a good place to start for a decade. And 256GB is totally out of the question. You haven't told us what the storage capacity of the old iMac was, but consider what your needs may be in five years.

When you setup your new Mac for the first time, connect your TM backup drive and, when prompted to transfer data from another computer, select the TM drive. Then choose only to transfer the User Account(s). This will leave behind the apps, utilities and other miscellaneous system garbage that you don't want on the new computer.

During the process you may be prompted to decide if you want the new Mac to inherit the backup history of the old Mac. In your case yes, you do. This will allow you to browse the TM backup drive with the TM application and recover any files you may find that didn't make the cut during migration.

Please see this guidance from Apple:

Recover all your files from a Time Machine backup - Apple Support

If your new Mac inherits your backup history - Apple Support

Following up:

Something that would be helpful in this situation would be to have a second backup of your data that is not on a TM drive, but rather a cloned copy made with Carbon Copy Cloner, SuperDuper! or other similar utility application.

With a cloned copy of your data, you don't have to rely on the convoluted steps required to move data from a TM drive to any other drive. You can simply and easily navigate your backup with the Finder and copy/paste or drag/drop your files where you need them. This is something you should never do with Finder and a TM backup set.

I understand that with a crashed iMac it's not possible now to make that cloned copy, but consider this food for thought for the future.

See this relevant thread from earlier today:

Time capsule retrieval - Apple Community

I’ll definitely defer to others here who are FAR more knowledgable in these “external drive” matters than I.