iMac won't finish booting..looking for ideas

[VideoBeagle]

Something happened on my iMac last night... I found the finder, dock, and more and more unresponsive, So
I restarted, and the boot up wouldn't finish. It being super late, I just didn't want to deal with it, so saved it for today.

Unplugged everything, tried, same thing...booted from an older backup (no curent one ) and it booted fine, and ran disk utility and that showed things were good. Ran disk warrior, that showed fine.

Booted back to main drive, in safe mode, brought me to the user select screen, and the main user account I couldn't get in... it would start logging in and beach ball. But the Guest account it went fine.

I set up a new account, but it would beach ball when I tried to get into that one.

Verbose mode runs thru the writeouts, then gets to the same point and beach ball.

I've spent the past X hours copying the drive contents to a new backup, and have downloaded El Capitan installer.. I figure the best idea is just to try to reinstall over the current and hope that fixes the issue, otherwise, do a clean wipe and install and go from there, rather than going deeper and deeper into fix and troubleshooting, BUT, I wanted to poll the brain trust if anyone has any thoughts I should try.

 

[Hellhammer]

You could run Apple Hardware Test just to make sure that the hardware is fine. If it is, then proceed with OS X installation. It sounds like a corrupted OS, so a reinstall should fix it.

 

[VideoBeagle]

You could run Apple Hardware Test just to make sure that the hardware is fine. If it is, then proceed with OS X installation. It sounds like a corrupted OS, so a reinstall should fix it.

Oh, Great idea! I had meant to do that earlier, then got all involved with the user accounts and forgot about it!

 

[VideoBeagle]

Well, hardware test came up fine,
but attempts to re-install over have failed...it would go then give me a install failed due to blah try again message
Blah was several times some script in the installer, then some mounting or unmounting error...it's 3am now, so I think I'll just erase the whole drive and start fresh tomorrow...I hate doing that but nothing else to do at this point I think.

 

[Hellhammer]

Well, hardware test came up fine,
but attempts to re-install over have failed...it would go then give me a install failed due to blah try again message
Blah was several times some script in the installer, then some mounting or unmounting error...it's 3am now, so I think I'll just erase the whole drive and start fresh tomorrow...I hate doing that but nothing else to do at this point I think.

Do you have a backup? If so, reinstalling will be easy as you can migrate everything from the backup. If the reinstall doesn't work, then it sounds like you have a failed hard drive.

 

[VideoBeagle]

Nope, no current backup :-(

I from Apple service diagnostics on the drive and it came up good I am right now just finishing a full system diagnostic just in case but I don't expect any problems :-(

 

[Fishrrman]

This is what backups are for.

Your problem demonstrates why I post again and again -- you MUST have a SECOND external drive with a fully-bootable copy of the OS on it.

If you had that, you wouldn't be flopping around like a fish, as you are now.

My suggestion:
Get an external drive.
Install a fully-bootable copy of the OS on it
Connect it to the problem Mac
See if it will boot that way
If it does, see if the internal drive will mount
If it does, GET WHAT YOU NEED TO GET OFF OF IT
Then, re-initialize and test the internal drive
Run Disk Utility's "Repair disk" on it five times in succession
If you "get a good report" each and every time, install a fresh copy of the OS onto it (or clone from your external).