Once in your installation screen, go to the Utilities menu and select Disk Utility. Select the option Install Mac OS High Sierra.

There's still (as of 10.13.4 beta) no way to merge containers, but I've found there is a way to pull in a volume from one container to another, given enough space: the Restore button in Disk Utility, with the special Restore to new volume checkbox A boot screen will appear. So, my situation is (still) that post-High Sierra upgrade, I ended up with three APFS containers, with one volume each. More Less Here's the Fix ] The first thing to know is that, when you format the external SSD as APFS, you'll be creating an APFS container and then the desired volume inside it-which you'll name. Reformat the Container device to Mac OS Extended (Journal) - Exit Disk Utility and then attempt to run the Mac OS install again. In Disk Utility, go to View | Show all Devices. This feature allows space to be shared between volumes in a container, and helps the Mac manage free space on its hard drives more efficiently To do this, follow the steps: - Run Internet Recover program by holding Command, Option R while powering up the Mac. Home Could not fix UUIDs for APFS volumes in containerĪPFS comes with space sharing concept, in which container is the basic storage unit, and in a container there're multiple volumes.