Reinstall of Mac OS

[Nisdrac]

Hi,

Yesterday I attempted to download & install High Sierra on my iMac 27. It downloaded fine but the install failed. When I restarted I received the no access symbol ie circle with a line through it along with a file with a question mark. After reading some threads I have managed to start with original OS (Yosemite) CD in the drive. I have run diagnostics on the HD and it is saying nothing wrong with it.

I have read a thread saying if I install Yosemite I will not lose any files. However, the thread states if I chose "Archive & Install". So far I have not had this option. So far I have chosen the language and from the next step run diagnostics. My questions are does this choose come later on, if not if I continue will I lose all my files?

Thank you in advance for any help.

 

[Fishrrman]

If you have the "full OS installer" in your Applications folder (check to be sure, there is a "full installer", and there is also a "stub installer" that is only about 15mb in size), in my opinion, your best course of action is to do this:

1. Get a USB flashdrive of 16gb capacity or greater.
2. Download either "Install Disk Creator" or "DiskMaker X" (I used IDC).
3. Use either app above to create a bootable copy of the installer on the USB flashdrive
4. Boot from the flashdrive and try the install again.

IMPORTANT:
BEFORE you create the flashdrive, make a copy of the installer somewhere else for safekeeping. It could be an "archival drive", anywhere you have sufficient space.