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Use target disk mode to move files to another computer. Help me!

Poncho

Poncho

macrumors 6502
Original poster
Jun 15, 2007
470
184
Holland
I want to move files from my Macbook Pro 2015 Retina with a Thunderbolt 2 port to my 2017 iMac with a Thunderbolt 3 port.

Apple says: 'To connect a Thunderbolt 3 (USB-C) port to a Thunderbolt 2 port, use the Thunderbolt 3 (USB-C) to Thunderbolt 2 Adaptor combined with a Thunderbolt 2 cable.'

I have done this. The cable is brand new as is the Thunderbolt 3 (USB-C) to Thunderbolt 2 Adaptor. Both bought from Apple.

So I plug everything in as directed by Apple. Start up the Macbook pro in Target Disc mode then start up the iMac. I do not see the Macbook pro as an external drive on my iMac.

I reversed the process and do not see the iMac as an external drive on my Macbook.

Am I trying to do the impossible? Have checked all connections. All are firm
 
It definitely should work, at least in one direction; Not necessarily both if one is running a newer OS version with file system differences.

But you could also do it without Target Disk Mode and just use network file transfer over the Thunderbolt network if that works
 
If what you're trying isn't working, I'll offer another way.

Use a hard drive (or a USB flash drive) to "move the stuff over".

For LOTS of stuff, use a hard drive.
If it's not so much, a USB flash drive will work fine.

Have the drive formatted to HFS+ (Mac OS extended with journaling enabled, GUID partition format).

When other methods won't work, this WILL.
 
What Thunderbolt cable are you using?
Click to expand...

Thunderbolt 2 cable.

Are you using FileVault?
Click to expand...

Not using Filevault on either Mac.

How are you doing this?
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Shutting down Mac then restarting holding down the 'T' key so that the screen shows the 'dancing' icon.

I'm glad it should work. Perhaps the new Apple adapter is broken. I have no way of testing it though
 
Does the connected MacBook Pro appear in the list of Thunderbolt devices on the iMac?

Do any extra drives appear in Disk Utility.app when the MacBook Pro is connected?
 
Does the connected MacBook Pro appear in the list of Thunderbolt devices on the iMac?

Do any extra drives appear in Disk Utility.app when the MacBook Pro is connected?
Click to expand...

No, I explored both avenues before posting. Just been up local computer repair store to see if they could test the Thunderbolt adapter. They couldn't, but said the Thunderbolt 3 (USB-C) to Thunderbolt 2 Adaptor is for connecting displays and that therefore I am asking the iMac to display a disk image rather than video data and that therefore what I am trying to do is impossible. Don't know whether to believe them though
 
Poncho said:
No, I explored both avenues before posting. Just been up local computer repair store to see if they could test the Thunderbolt adapter. They couldn't, but said the Thunderbolt 3 (USB-C) to Thunderbolt 2 Adaptor is for connecting displays and that therefore I am asking the iMac to display a disk image rather than video data and that therefore what I am trying to do is impossible. Don't know whether to believe them though
Click to expand...
They obviously don't know anything about Thunderbolt or Macs. Ignore them.

There may be something wrong with the Thunderbolt 2 cable. Have you tried connecting any other Thunderbolt devices?

Did you try all the Thunderbolt ports on the MacBook Pro and iMac?
 
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joevt said:
They obviously don't know anything about Thunderbolt or Macs. Ignore them.
Click to expand...

They probably just saw Mini Display Port and didn't know Thunderbolt was a thing.

But on that point, OP, are you sure that your Thunderbolt 2 cable is actually TB 2 and not a Display Port Cable that branded itself as "compatible" with Thunderbolt ports?
 
Outside chances (some have already been covered) but have seen them all:
  • One (or both TB) ports are bad
  • TB 2 port is actually just a Mini-Display port
  • TB cable is bad/defective
  • TB 3 cable is really just USB C cable
  • Drive on TDM Mac is bad
  • Some devices are picky about cable direction (reverse TB3 cable direction to rule out)
So the machine you want to copy from...does it boot and run normally?

Do you have any way to test the TB port(s) on both machines?

When you have it connected in TDM, is the hardware seen in System Report (you should see something plugged in under: Port Status.

Somebody mentioned encryption...as I recall, you would get prompted to authenticate.
 
But on that point, OP, are you sure that your Thunderbolt 2 cable is actually TB 2 and not a Display Port Cable that branded itself as "compatible" with Thunderbolt ports?
Click to expand...

Here's some pics of the box
IMG_5769.JPG
IMG_5770.JPG
IMG_5771.JPG
 
  • One (or both TB) ports are bad
  • TB 2 port is actually just a Mini-Display port
  • TB cable is bad/defective
  • TB 3 cable is really just USB C cable
  • Drive on TDM Mac is bad
  • Some devices are picky about cable direction (reverse TB3 cable direction to rule out)
Click to expand...

Thanks for sticking with me all, on this.

Both Macs are running and booting perfectly and all ports work.

When you have it connected in TDM, is the hardware seen in System Report (you should see something plugged in under: Port Status.
Click to expand...

Answer to this is no, it is not.
Screen Shot 2020-09-02 at 21.06.57.jpg
 
Poncho said:
No, I explored both avenues before posting. Just been up local computer repair store to see if they could test the Thunderbolt adapter. They couldn't, but said the Thunderbolt 3 (USB-C) to Thunderbolt 2 Adaptor is for connecting displays and that therefore I am asking the iMac to display a disk image rather than video data and that therefore what I am trying to do is impossible. Don't know whether to believe them though
Click to expand...
That adapter is specifically not for video use. It can be used to connect a Thunderbolt Display but standard displays cannot be connected through that adapter.
I just checked and the adapter will not show in the System Report as connected to the computer if no device is attached to it.
 
As mentioned, that cable should be fine (outside the rare chance of a defective cable).

Sorry...I got a few things backwards: I thought you had a TB 3 cable, not 2. TB 3 is more complicated with third party cables as to which support what...they look the same as USB C cables. Disregard this.

The fact that nothing shows connected usually means a cable/adapter/port is bad.
 
Thanks all, some really good group information coming together here. Frankly, I now suspect the Adapter dongle.

What OS version is on both the Macs?
Click to expand...

Am using OS Sierra on both Macs. In fact, the Macbook Pro is running a Carbon Copy Clone of my iMac. I Carbon Copy Clone a back up of my iMac to a Samsung T5 and then Carbon Copy Clone that to the Macbook Pro. There are reasons for doing this. Work-related. Would like to break free from OS Sierra but can't upgrade because I have to run a specific piece of big software (Adobe CS3) that is not supported on High Sierra and upwards.
 
chrfr said:
That adapter is specifically not for video use. It can be used to connect a Thunderbolt Display but standard displays cannot be connected through that adapter.
I just checked and the adapter will not show in the System Report as connected to the computer if no device is attached to it.
Click to expand...
Displays can be connected with that adapter only if the displays are connected to a Thunderbolt device - the adapter itself does not have the ability to convert Thunderbolt to DisplayPort (it is an adapter and not a full Thunderbolt controller), but any Thunderbolt controller in the chain can do that - up to one display per Thunderbolt 2 controller, two displays per Thunderbolt 3 controller, two displays max per Thunderbolt host controller/bus.

I think MacBook Pro 2015 has firmware for FireWire target disk mode - you'll probably be able to see that when you have a FireWire port added using Thunderbolt. In that case, you'll see two icons dancing around the screen - one FireWire and one Thunderbolt.

Add FireWire to the iMac, then connect them with FireWire cable, then only the FireWire icon remains and you should see the disk on the iMac.

My Mac mini 2018 doesn't have FireWire firmware for target disk mode - I think it supports Thunderbolt and USB target disk modes.

If there's a problem with the internal drive of the MacBook Pro connecting with Target Disk Mode, then what if you also had a USB drive to the MacBook Pro? Then maybe the USB drive would appear on the iMac while the MacBook Pro is in Target Disk Mode.

But the big problem here is that the MacBook Pro doesn't appear connected even when not using Target Disk Mode - suggesting a problem with Thunderbolt. For example, you are supposed to be able to connect Macs (or PCs running Windows or Linux) with Thunderbolt for Thunderbolt networking - in that case each computer should appear to the other as a connected Thunderbolt device.
 
Poncho said:
Am using OS Sierra on both Macs. In fact, the Macbook Pro is running a Carbon Copy Clone of my iMac. I Carbon Copy Clone a back up of my iMac to a Samsung T5 and then Carbon Copy Clone that to the Macbook Pro. There are reasons for doing this. Work-related. Would like to break free from OS Sierra but can't upgrade because I have to run a specific piece of big software (Adobe CS3) that is not supported on High Sierra and upwards.
Click to expand...

Well, was a long shot anyway since it didn’t work either direction, but I was thinking maybe if they were on vastly different OS releases one might be formatted with a very new revision of APFS that the other couldn’t read, and the other some similar issue.
But wow, CS3. Gonna suck when the hardware breaks and you can’t get a Mac that runs Sierra natively anymore.
 
But wow, CS3. Gonna suck when the hardware breaks and you can’t get a Mac that runs Sierra natively anymore.
Click to expand...

LOL! Then I spend major bucks on a new machine with bags of RAM and run Sierra inside a Virtual machine!
 
Displays can be connected with that adapter only if the displays are connected to a Thunderbolt device - the adapter itself does not have the ability to convert Thunderbolt to DisplayPort (it is an adapter and not a full Thunderbolt controller), but any Thunderbolt controller in the chain can do that - up to one display per Thunderbolt 2 controller, two displays per Thunderbolt 3 controller, two displays max per Thunderbolt host controller/bus.

I think MacBook Pro 2015 has firmware for FireWire target disk mode - you'll probably be able to see that when you have a FireWire port added using Thunderbolt. In that case, you'll see two icons dancing around the screen - one FireWire and one Thunderbolt.

Add FireWire to the iMac, then connect them with FireWire cable, then only the FireWire icon remains and you should see the disk on the iMac.

My Mac mini 2018 doesn't have FireWire firmware for target disk mode - I think it supports Thunderbolt and USB target disk modes.

If there's a problem with the internal drive of the MacBook Pro connecting with Target Disk Mode, then what if you also had a USB drive to the MacBook Pro? Then maybe the USB drive would appear on the iMac while the MacBook Pro is in Target Disk Mode.

But the big problem here is that the MacBook Pro doesn't appear connected even when not using Target Disk Mode - suggesting a problem with Thunderbolt. For example, you are supposed to be able to connect Macs (or PCs running Windows or Linux) with Thunderbolt for Thunderbolt networking - in that case each computer should appear to the other as a connected Thunderbolt device.
Click to expand...

Thanks for all that. I like your Firewire Target Disk Mode idea. I am going to have to study the rest of what you say though, as it's pretty complex!
 
Assuming you have a thunderbolt to ethernet adapter, use an Ethernet cable. For Target disk mode here's the instructions https://support.apple.com/en-gb/guide/mac-help/mchlp1443/mac
Just a thought though, if you're using the carbon clone on both machines are they both called the same computer name, maybe that's an issue?
You have a SSD. Assuming that when you plug it in to the MB it's seen as a hard drive, just use that to transfer the info?
 
Last edited:
Poncho said:
LOL! Then I spend major bucks on a new machine with bags of RAM and run Sierra inside a Virtual machine!
Click to expand...

Might not necessarily even be possible if it’s an Apple Silicon Mac, but time will tell. - Different discussion, but yeah - Your employer should consider Affinity and other Adobe alternatives... Or a CC subscription I guess
[automerge]1599087412[/automerge]
McScooby said:
Assuming you have a thunderbolt to ethernet adapter, use an Ethernet cable?
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Pretty sure that doesn’t work with Target Display mode, and Thunderbolt already works as a network connection between devices if you were thinking of a normal networked transfer
 
casperes1996 said:
Pretty sure that doesn’t work with Target Display mode, and Thunderbolt already works as a network connection between devices if you were thinking of a normal networked transfer
Click to expand...
It wouldn't, but I'm really confused now so sorry. OP has iMac & uses CCC to copy iMac drive and transfer this to the MB.
The purpose of the whole Thunderbolt cable was simply to transfer info from iMac to MB, in reality cutting out using the T5 SSD which is why target disk has been raised.
Issue here I think is that using CCC (which you need for work) is unless you noted all changes done on one machine (iMac) to transfer to MB you're not going to get the same outcome with both machines as settings won't be transferred across, target disk doesn't work like CCC, it just saves you plugging in an external drive and copying the contents from it.
As OP has an external SSD (T5).
The solution is just to use that & avoid CCC as you would've lost ability when using the TB cable process.
Have I got this right?
 
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