Success creating APFS High Sierra external startup volume

I eventually got my external SanDisk Extreme 900 portable SSD drive converted to an APFS High Sierra developer beta 1 startup volume, but it wasn't easy. Here are the details:


I originally installed High Sierra beta 1 on the SanDisk without converting it to APFS, and it successfully booted as the startup volume for my 15" MacBook Pro (Late-2016) with Touch Bar. Very easy.


Later, I restarted and held down Command-R to boot into the SanDisk's restore volume. I then ran High Sierra's Disk Utility and used its Edit menu to convert the SanDisk startup volume to APFS. Disk Utility reported success. Also very easy.


The trouble started when I tried to reboot into the APFS SanDisk startup volume from the restore volume after converting it to APFS. When I chose the SanDisk as the startup volume. I received an alert saying 'You can't change the startup disk to the selected disk," giving the reason "Building boot caches on boot helper partition failed." I then chose to restart into the Sierra internal startup volume but immediately held the Option key down so I could choose to restart into the SanDisk restore volume again instead. I did this several times, and I ran the High Sierra Disk Utility's First Aid each time in an attempt to fix the reported problem. Disk Utility always reported success. Nevertheless, it still would not let me restart by choosing the SanDisk as the startup volume, sometimes giving the reason "Building boot caches on boot helper partition failed" and other times the reason "Running bless to place boot files failed." Booting back into Sierra on the internal drive instead, and then trying to choose the SanDisk startup volume from the System Preferences Startup Disk pane, failed and gave the same error reasons. When Option-restarting as a last resort, I sometimes saw the SanDisk restore volume but not its startup volume, and other times I saw both the SanDisk startup volume and the SanDisk restore volume.


I finally chose to Option-restart and boot into the SanDisk startup volume instead of the SanDisk restore volume, on a lark, and -- it worked! I was at last successfully running High Sierra booted from the SanDisk APFS High Sierra external startup volume.


I guessed that the system routines on my MacBook Pro that run when I try to choose a new startup volume might have had some kind of problem recognizing an external APFS High Sierra drive as a valid startup volume. I noticed that doing a Get Info on the SanDisk in both High Sierra and Sierra Disk Utility reported "Bootable No". Get Info does properly report that it is an APFS volume.


Now that I had the APFS High Sierra SanDisk running as the startup volume, I tried using the High Sierra System Preferences Startup Disk pane to restart into the SanDisk startup volume again. This time it did not report an error and let me proceed, and it booted successfully.


I then used High Sierra System Preferences to reboot into Sierra on the internal drive, and then as a final test I tried using the Sierra System Preferences Startup Disk pane to restart using the APFS High Sierra SanDisk startup volume. It worked, and all is right with the world once again. (Well, almost all. Disk Utility's Get Info still reports that the SanDisk drive is "Bootable NO", but I assume that is an HFS+ thing that I no longer have to worry about.)

Replies

Thanks for posting this . . . solved my external startup problem as well.

I appreciate the answer you posted, cheeseb. It gave me a starting place for my own success. However, following your method as best I could did not yield repeatable success for me, for what reason I am not sure. I considered the caveat from Apple that converting a file system to APFS separately from OS installation would not make a volume bootable in this early beta.

Instead, the installer's automatic conversion of the file system to APFS was the way to go if I wanted macOS 10.13 to boot from APFS. I decided to try that. My problem was that I had only one drive on which I was willing to install High Sierra right then, a SanDisk Extreme Plus microSDXC 64GB card (in an adapter) in the SD slot of my mid-2013 MacBook Air 13-inch.


As I recall, these are the steps that worked for me.

1. Format the media as a Mac OS Extended (Journaled) volume.

2. Download the macOS 10.13 helper app from the WWDC 2017 SDK page

3. Install the OS on the volume. (You need it installed to get the right version of Disk Utility on the recovery partition.)

4. Boot into the 10.13 recovery partition.

5. Open Disk Utility.

6. Select the macOS 10.13 volume and run Edit > Convert to APFS.

7. Quit Disk Utility.

8. Reinstall macOS 10.13 over the initial install (this is what made the volume bootable).

9. Set Startup Disk to the macOS 10.13 volume.

10. Boot into it and confirm you can set Startup Disk and boot into either Sierra or High Sierra at will.

Very helpfull, I will try this, I have a PCI card in a MacPro with a 512GB SSD StartUp disk and it sees it as an external drive, I had nothing but crap with that drive and APFS like you said HFS+ works fine, I stripped the machine now from other harddrives for testing... so would be interesting to see if it works...

This was a known bug. I think, it's fixed in b4.

Well I can't get it to work on a PCI SSD card on a Mac Pro, will try again tomorrow again HFS+ boots fine with 10.13 I took all drives out, and reset the PRAM and SMC no luck so far, APFS won't boot, also with apple it's not clear which installer you have, in the past they would name the installer beta 3 or something, now they just name it beta, but you have no clue of what version it is until after installation

I ran into similar. I have a 2010 Mac Pro (5,1). I installed macOS High Sierra GM candidate to external HDD drive after APFS formatting (erase), after firmware update provided by macOS High Sierra GM installer. Worked like a charm. Turned on FileVault. Success. Boots just fine. My primary boot drive with HFS+ Journaled with FileVault turned on would not convert to APFS. Error every time. Turned off FileVault. One day to decrypt. Convert to APFS worked. Could not bless to boot to macOS High Sierra GM that I installed while HFS+ with FileVault on. I followed suggestion to install macOS High Sierra GM over my already existing install. This worked, though took a while longer than any previous macOS updates or installs. I can now boot off of either of my HDD APFS partitions on a Mac Pro. One has FileVault turned on. I'll be turing on FileVault on my main drive next. I lived dangerously and did not backup this drive. I would recommend backup before doing this upgrade. Of note, on my initial install of macOS High Sierra GM, I was presented with a firmware update for my 2010 Mac Pro. This is the first build of macOS High Sierra that presented this. Prior to this firmware update, I was not able to boot off of any of my HDD drives with APFS. This now resolved.

hi all,


think i may have a solution to this problem..


macpro, external samsung ssd connected via usb for main os drive


did os upgrade from sierra, once complete, control r into recovery, terminal, diskutil apfs convert /dev/disk3s1


all done and no errors..


reboot


won't except drive as boot.. round and round, disk reapir, etc etc..


back into recovery and reinstall osx, complete but can't update preboot for new apfs install...


had a little think....


back into recovery, terminal, diskutil apfs updatePreboot /Volumes/disk


ran without an issue, did try with /dev/disk3 but caused issues, ran with /Volumes/disk cleanly


reboot into recovery, ran disk util, all clean, choose startup disk, no complains!!!! rebooted and all worked great, rebooted same again.. hurrah!


seems when you do convert it doesn't write the preboot for the new apfs volume so won't boot to it, if you wtrite the preboot for the volume it works great..


adolf.