#Macos high sierra usb installer install#
This was another important lesson: when run in Sierra, the High Sierra installer will not install to an external disk unless it is in HFS+ Journalled format.ĥ: Try the proper installer, running in High SierraĪt this point, I lost heart. The installer refused, demanding that the destination volume be in HFS+ Journalled format, not APFS. Now that I had my SSD in APFS, I tried running the High Sierra installer in Sierra, to install High Sierra onto it. Therefore, if you want to make yourself a dual-boot Mac, you should be able to use this process: format the SSD from Disk Utility on a bootable installer, then install from there. On reflection, what I should have done then was to have restarted with the Option key held, to enter the boot menu, and selected the SSD from there, if it had decided to reappear. This works, but at the end of the install, when my iMac restarted, the SSD was nowhere to be seen, and I was back into Sierra. I formatted the destination SSD in APFS (non-case-sensitive, unencrypted), then set the installer to work on it. I then restarted my iMac from that, and opened Disk Utility. Using my installer app, the instructions here (which I had to hastily revise after Apple changed them following the release), and a 16 GB USB memory stick, I created a bootable High Sierra installer. I had learned one lesson which Apple had not explained: the High Sierra installer will only convert internal SSDs to APFS. Once I had downloaded the proper installer, I repeated the installation, only to discover that the external SSD had been left in HFS+ format. Although it did install onto the SSD, there were several things wrong with it, including the fact that the drive had not been converted from HFS+ to APFS. My first attempt was marred by Apple releasing the wrong High Sierra installer in the first place.
#Macos high sierra usb installer mac#
So why not install High Sierra on my external SSD, and then boot from that when I wanted to test or try something in High Sierra? Such dual-boot systems have been commonplace, and for a while one of my Mac Pros was triple-boot, with its four internal hard disks. For the time being, until High Sierra is supported on Fusion Drives, I wanted to continue working in Sierra. I wanted to be able to start up in High Sierra, running on Apple’s new file system, APFS, but didn’t want to go the whole way to running only High Sierra. My original plan seemed straightforward: I have an iMac17,1 with an internal 2 TB Fusion Drive, and a spare USB3 750 GB SSD.
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