High Sierra Update to 10.13.6 fails.

Not sure what's causing this, but installing from the direct download image worked for me. First time I've ever had to do that.

https://support.apple.com/kb/DL1970

I had this problem for a long time, since installing Mac OS High Sierra I have not been able to install any system updates.

The incremental system updates download fine from the App store then I press restart. The computer changes to the black screen with the white Apple and the the message installing update, the progress bar does not move, after a couple of minutes the Macbook restarts without installing the update and leaving a folder named macOS Install Data on my hard drive.

I just tried to install the 10.13.6 incremental update with same result.

For every update I have tried the following:

- Restarting in Safe Mode to install.

- Reseting the NVRAM and the SMC.

- Reinstalling Mac OS High Sierra from recovery partition and internet recovery.

- Downloading combo update to the MacBook.

- Running Disk First Aid from recovery partition.

- Enabling Root User to install.

Non of these actions have resolve the issue. The only method I have found to work is downloading the combo update on another Mac and then installing it on the Macbook Prom using target disk mode.

Using target disk mode lets me install the updates but it is a hassle and a cumbersome process, any help in resolving the issue would be really appreciated, I want to avoid formatting my hard drive and string from scratch desperately.

I have a MacBook Pro mid 2015 with Mac OS 10.13.5 install, 16GB ram and plenty disk space available.

Thanks in advance.

I am having the same dilemma. Tried the same steps as you but when I mount my iMac (Mid-2017 Fusion Drive) to a 2011 MacBook Pro running 10.13.5 it says it cannot write to the Fusion mounted drive. When trying to choose that drive to apply the 10.13.6 Combo Update it has a yellow exclamation mark on it.

I also have the 2017 TouchBar 13" MBP running Mojave on it my iMac will not appear as connecting my USB-C cable between my iMac and the TB MBP in target disk mode like it will above.

Frustrating.

The iMac will just start booting, apple logo and bar start to go across screen and it shuts down.

I'm hoping I don't have to completely wipe and re-install all my apps again. I've done Time Machine restores before and it never seems as clean as I would like so while I have data backed up, I would rather not have to set everything up again. Any further suggestions on how to successfully apply the Combo Update using Target Disk Mode from either of my MacBook Pro's? As a side note, I created a new partition on my TB MBP and installed 10.13 on there as well (not sure if it put on 10.13.5 or .6, I think it was .6) and still can't get my iMac to mount on the Finder in Target Disk Mode.

Have downloaded 10.13.6 on two MacBook pros. The first went fine when downloaded restarted and installed, no problem. The other, newer machine downloaded then reverts back to update.

Also wanted to add that of course trying to just launch the 10.13.6 Combo Update installer on Mojave will fail as it says it is for a computer running High Sierra.