Target Disk Mode from iMac - receiving macbook not showing data

[rkg18]

My iMac (Retina 5K 2017) got stalled during OS update due to lack of storage space and it prompted to go into Target Disk Mode. I purchased a cable and adaptor needed to connect to my 2013 MacBook Pro. MacBook recognizes the iMac as HHD but when I click on the disk there is no data showing. Is there anything I need to do on my iMac in order for the data to show up?

My hardware is the following:
iMac (Retina 5K, 27-inch, 2017) to MacBook Pro (Retina, 13-inch, Late 2013)
iMac - Thunderbolt 3
MacBook Pro - Thunderbolt 1
Connection - Thunderbold to Thunderbold cable + Thunderbold 2 --> Thunderbolt 3 adaptor

Thanks in advance.

 

[Fishrrman]

What version of the OS on the iMac?
What version of the OS on the MBP?

 

[rkg18]

MBP is on 10.14.6
iMAC is also on Mojave but can't recall the exact version number.

 

[Fishrrman]

Can the iMac be booted AT ALL?
Can it be booted into "safe mode"? (hold down shift key at boot)

Can it be booted into INTERNET recovery?
Command-OPTION-R
at boot ???

 

[rkg18]

It can be rebooted, goes into Target Disk Mode after Command-Option-R and selecting Disk Utility. The iMac does show up on my MBP as HHD, however, when I open the folder it's empty. I wonder if either the OS or the ports aren't compatible as my MBP is so old??

Can it be booted into "safe mode"? (hold down shift key at boot)

Can it be booted into INTERNET recovery?
Command-OPTION-R
at boot ???

 

[Fishrrman]

What I would do.

Get an EXTERNAL USB3 drive. I would suggest an SSD, doesn't have to be large, 512gb or even 256gb is fine. Even a cheap 128gb SSD could do the job.

Connect it to the MBP. NOT to the iMac.

Boot the MBP to INTERNET recovery
Command-OPTION-R

Get to the online utilities.

Open disk utility.
Go to the view menu and choose "show all devices".

Format the external drive to APFS.

Close disk utility and open the OS installer.

Now install a fresh copy of the OS (you should be offered Big Sur by the Apple servers) onto the EXTERNAL drive. The install will take a little time, be patient.

When the install is done, create a simple user account -- just a username and password is all you need (don't bother with iCloud, etc.).

Now, power down and connect this bootable external drive to the iMac.

Press the power on button and hold down the OPTION key continuously until the startup manager appears.

You should see the external SSD as a choice.
Choose it and let it boot up.

Now you should be able to see the iMac's internal drive (make sure your finder preference settings are correct).

Are you able to access it?
See the data on it?

If so, START DELETING STUFF from the internal drive.
Movies are a good place to begin. JUST GET RID OF THEM.

You want to "open up" 15-20gb of space.
Yes, this means throwing stuff away.

When you get about 20gb free, NOW try a reboot.
What happens?

In the future, try to keep the drive from getting so "full".