APFS systems can only be restored to internal SSDs

Hello Alexome,

The Apple moderators do not remove posts just because they are critical. You comment about “friendliness” is probably the issue.

Can you describe the exact problem? I’m sure that this is no purposeful restriction over your data. APFS is just brand new and lots of things don’t work. If you are attempting something even slighly outside of the mainstream of what Apple expects, you can expect problems.

Generally speaking, Time Machine can only restore either Time Machine backups (which must reside in an HFS+ drive) or APFS snapshots, which must already be on the APFS drive.

You specifically said you are attempting to restore APFS to an external SSD. Time Machine doesn’t do that at all. There is a restore functionality in Disk Utility, but it doesn’t have anything to do with Time Machine. I can definitely see the restore functionality being flaky. Recent versions of Disk Utility are very buggy. Also, you haven’t said anything about the external SSD. There are a number of different bug that could impact that.

So, if you could clarify some of those questions, we might be able to help.

I don't see what the problem is. High Sierra only support booting APFS on internal SSDs. It is not going to allow a restore to a system that might not boot. There are ways around that, but not via Time Machine. That message even suggests one way.

Have you done this kind of operation before? I don't know what kind of data you plan to put on that data drive. There are significant portions of user data that are not backwards compatible, even between minor versions.

Time Machine is great for backups, but that is all it is good for. It is a very poor choice for archives or vanilla restore images. You can use Disk Utility to backup and restore entire drives. That should work although Disk Utility is very buggy. In many cases you will just have to keep trying until it works.

You have to be very careful with both restores (either via Time Machine or archives) and clones. macOS simply doesn't support them in a general sense. They will work in certain contexts, but not in all contexts. There are a number of unique identifiers stored in individual user's home directories and elsewhere on the system. If you clone machine A (or user account A) and physically destroy the old system, the clone will work fine. But you will have problems if you try to run both simultaneously. Things like Handoff and iCloud will not work properly because the two environments are no longer sufficiently unique.

macOS Recovery does work as advertised. It simply never advertised the features you are looking for. I don't know whether or not Time Machine can, should, or has ever, allowed a restore to an external disk. I've never tried it.

I do know that APFS adds all kinds of complexities. When Mojave came out, Apple cut off my old 2011 test machine so I had to buy a new one and make my old production machine my new test machine. I have some funky, not-quite-suppored practices of my own. When I tried one of those when installing High Sierra, it didn't work. The installer refused to install onto the disk as I had configured it. But it only complained on the new machine. My old hack worked fine on the old machine. That was certainly annoying, but not a big deal.

It sounds like what you are attempting is something very similar to what I was trying to do. The system might not let you install the OS onto an APFS system. I could do it on my 2014 machine, but not my new 2017. Is there a technical reason for this? I don't know.

I'm definitely the type of developer you are talking about. I think I have 16 boot volumes of various versions, not counting virtual machines. I would never use Time Machine for those. Time Machine is only for my production system and only if it gets stolen or dies somehow. I would never, ever share a "Library" folder with another machine. I learned that lesson the hard way and don't intent to repeat it.

What exactly are you trying to accomplish with Time Machine? Are you doing development or testing? I generally don't do that kind of funky stuff with APFS volumes because they are so new. I have made low-level "backup" and "restore" operations via Disk Utility on older OS versions. I have also make big disk images of older OS versions. Sometimes those work and sometimes they don't. In particular, I recently tried to restore a couple of those older OS versions onto my own Samsung 850 and they didn't work at all. Those old OS versions don't have the firmware for that drive. Such is life. I have other SSDs and some older HDDs to use instead.

Instead, I normally setup test machines fresh and reinstall the software I need. Since I'm just testing, I don't need much 3rd party software. If I need to blow it all away and start from scratch, it isn't too much work, especially with fast SSDs. With APFS, I have used snapshots to easily restore to an old version. I also use VMs that have their own snapshots. But Time Machine is not appropriate for this kind of work. It is a consumer tool, not a development and testing tool.

Alexome wrote:

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Time Machine should not be great for backups. It should be great for restoring its backups. Backups by themselves have no value.

I am sure it is news for many others that this macOS Recovery utility does not work as advertised.

Consider the use of bootable clones instead. Carbon Copy Cloner

and Super Duper are good at creating bootable clones.

My experience is primarily with CCC. As a matter of fact, I just recently

botched up my internal drive on a MacMini Server trying to get Windows

on it. The internal was an SSD, APFS. I formatted and external HDD to

APFS (yes that is correct it does work, just not recommended). Used CCC

to clone the APFS partition to it and rebooted to the APFS formatted HDD

(yes an external APFS formatted hard drive will work, just not recommended).

Then totally erased the internal SSD and reformatted as APFS, cloned the

external bak and worked just fine.

I have never been a big fan of Time Machine and have used CCC

since version 1.0 and it was always reliable.