Booting from external usb HD drive with High Sierra does not work on Mojave

Hi Matti,

Thank You for your comment. It helps me to find the Mail Stuff. I have compared structures stored on Mojave with my archived Mails. They are totally different. For details you can consult screenshots attached. So, the question is: Is it a good idea to continue this type of archiving the old mails, or not? At the moment, I think I have to finish this method of working, and instead of it, the really important mails I can save directly in ".eml" format from Mail APP. I think, it could be better solution. ...

Best Regards, László

Hi Fuzzymo,

Thank You for your correct answer. It is clear! Such is life …

Just some comments: 

1.: I have migrated my important stuff manually, because the Migration Assistant reported an incredibly statistic for me before starting.

2.: I have got a different proposal from Apple’s Help Desk yesterday for this issue: he advised to convert my old HD to an APFS format via making a disk image. It was failed during rewriting the disk, because changing the file system dos not supported by Disk Manager App. Anyway, I have tried the direct converting functionality of Disk Manager, but the product HD was not bootable even on my MacBookPro (2011) with High Sierra. After that I have posted my problem here.

3.: Anyway, I wanted to save my Mail stuff stored on my old HD. but I do not know, where is it stored on disk: I could not find this stuff by Finder App. That is why I wanted to boot from my old HD to Mojave. So, I have to forget this mails …

Thank You for your cooperation.

Best Regards

Dr. Józsa, László

from Hungary

Hi Fuzzymo,

Thank you. It seems to be a good idea for migrating from High Sierra to Mojave on my old external HD. Probably I will try it in the near future.

I should think it out, because, there are some APPS, which do not work in Mojave (for example: ScanJet for my EPSON XP-700 multifunction printer and Camera Windows for my Canon IXUS 1000 HS camera etc). Do not forget, I have a MacBook Pro with High Sierra too. So, at the moment I do not want to do this upgrade.

Anyway, your recommendations are very useful, thanks for them.

Best Regards, László

Hi Garry,

I wanted to save my Mail stuff stored on my old HD. but I do not know, where is it stored on disk: I could not find this stuff by Finder App. That is why I wanted to boot from my old HD to the new iMac. Anyway, practically all of my important stuff was migrated successfully, manually by Finder, from the old HD.

Best Regards, László

OK, thanks!