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I'm working happily on my powerful 27" iMac late 2013 booted from an external SSD running 10.13.6. I also sometimes run 10.9.5 - in both cases because of legacy applications. I've tried to install a "modern" system on another external SSD (automatically converted to AFPS), but the new and old systems don't "see" each other, so I can't switch between them, and the computer jams. Is there a way around this problem?
iMac 27″, macOS 10.13
I assume you know that the most "modern" OS you can use is 10.15 Catalina, and that requires a drive using the APFS format. Your 10.9 and 10.13 OSs require the older HFS+ drive format.
hsmultimedia wrote:
...I've tried to install a "modern" system on another external SSD (automatically converted to AFPS), but the new and old systems don't "see" each other, so I can't switch between them, and the computer jams. Is there a way around this problem?
Since you apparently have two external drives with these different OS versions, the easiest way to switch between them would be to reboot the Mac while holding the Option key. This forces the Mac to scan each connected drive for an available bootable OS. You then select which OS you wish to boot at that time.
As for the OSs "seeing" each other... the 10.9 Mavericks OS is ignorant of the APFS drive format and cannot interact with it. I think the 10.13 High Sierra may have that ability, but it may not. macOS 10.15 Catalina can read and write to the older HFS+ drives without issue.
I assume you know that the most "modern" OS you can use is 10.15 Catalina, and that requires a drive using the APFS format. Your 10.9 and 10.13 OSs require the older HFS+ drive format.
hsmultimedia wrote:
...I've tried to install a "modern" system on another external SSD (automatically converted to AFPS), but the new and old systems don't "see" each other, so I can't switch between them, and the computer jams. Is there a way around this problem?
Since you apparently have two external drives with these different OS versions, the easiest way to switch between them would be to reboot the Mac while holding the Option key. This forces the Mac to scan each connected drive for an available bootable OS. You then select which OS you wish to boot at that time.
As for the OSs "seeing" each other... the 10.9 Mavericks OS is ignorant of the APFS drive format and cannot interact with it. I think the 10.13 High Sierra may have that ability, but it may not. macOS 10.15 Catalina can read and write to the older HFS+ drives without issue.
Unfortunately, it doesn't seem to work. I've installed Catalina on the external SSD #2. On the external SSD #1, I have High Sierra (10.13.6), which is the one I usually work on. On the internal SSD, I've got Mavericks (10.9.5) and A Bootcamp/Win7 installation, which I use for a special work-related program. As mentioned above, the many systems are used for various legacy programs.
When I reboot pressing the Option key – with both SSD #2 and SSD#1 attached – the only reboot options I get are the internal Mavericks and Win7 partitions! It seems that the AFPS formatted partition on the SSD#2 so confuses the computer that only the internal SSD is detected.
When I detach SSD #2 and reboot with the option key pressed, I can choose between all the available systems.
The iMac is 27", late 2013, 3,5 GHz core i7 with 24 GB ram.
hsmultimedia wrote:
When I detach SSD #2 and reboot with the option key pressed, I can choose between all the available systems.
What happens if you disconnect SSD #1 instead of #2?
Macs can be very picky about the drives being used, especially for booting. It is possible one of the external SSDs has a problem or just isn't compatible with the other one, at least for booting.
Have you tried rEFInd yet? rEFInd is just a script which places the rEFInd files onto the hidden EFI partition. There is no rEFInd app running within macOS except when you execute the installation script. Removing rEFInd should be as easy as using the script to remove it or by manually deleting the rEFInd folder from the hidden EFI partition. IIRC, rEFInd will automatically scan for bootable volumes when rEFInd launches (assuming you allow rEFInd to be the default Startup Disk) in order to populate its boot menu. I believe I just copied the rEFInd folder onto a USB stick once and booted to the rEFInd USB stick without customizing rEFInd at all & it detected all my connected bootable volumes.
Thanks for your swift reply. I'll try to install Catalina - and then try the option key.
You're welcome. 🙂
You can use the rEFInd boot menu/manager which should make switching between old & new operating systems easier:
Imac 27" late 2013 + "modern" startup system on external ssd
