Random Reboots

[Denomfug]

Hey I'm new and was wondering if there was an one on here currently that could help me with my mac problem.
It randomly started rebooting itself
I can't get disk recovery to open using command option r p
It just goes to the Apple starts booting then 3/4 of the way restarts itself. If I hold option I get 2 hd icons one regular one that system recovery but both have the same result as above.
You guys got anything ?
Thanks in advance
D.

 

[Spawn_Dooley]

can you provide as much info about your iMac please, model Mac OS X version etc

 

[Denomfug]

Not really it's an i mac form 2008 I had Yosemite other than that I can't get into the about this mac to tell you more . I never thought to write this stuff down sadly.

 

[honestone]

Have you been making any backups to an external device?

Also, do you have another Mac available? If it has a Firewire 800 port, then your iMac can be attached to it and booted up in "Target Disk Mode". What will happen is that the iMac's internal drive will appear on that other Mac's desktop, and tools on that other Mac can be used to check out/repair the iMac's drive.

By the way, what are you using to make posts here?

 

[Denomfug]

Well I made a el capitan install recovery disk on my external hd and am currently trying to reinstall from that. I used my brothers MacBook. And I'm making posts on here from my phone.

 

[Denomfug]

Well I made a el capitan install recovery disk on my external hd and am currently trying to reinstall from that. I used my brothers MacBook. And I'm making posts on here from my phone.

Actually now when I'm trying to start from the ext.hd the load bar gets about 3/4 and reboots itself . I know the ext. Hd is is working correctly . What could be causing this ?

 

[honestone]

Actually now when I'm trying to start from the ext.hd the load bar gets about 3/4 and reboots itself . I know the ext. Hd is is working correctly . What could be causing this ?

First of all, do you have a backup of the stuff on the iMac's internal hard drive?

Secondly, assuming you have no backup, can you afford to lose everything off the iMac's drive? Assuming that is the case, what you need to do is the following:

1. Purchase a Firewire 800 cable.

2. Plug one end of the cable into a Firewire 800 port on your brother's MacBook, and the other end to a Firewire 800 port on the iMac.

3. Boot up the MacBook.

4. After that boot up completes, boot up the iMac while holding down the T key.

5. Once that completes, as I mentioned above (and assuming the drive is OK), the iMac's internal hard drive will appear on the MacBoo's desktop. You can then use Disk Utility on the MacBook to Verify and Repair the iMac's drive, and then use Disk Utility to Erase and Format that drive. Then, assuming you have the file "Install OS X El Capitan" on the Mac Book, perform a clean, "virgin" installation of El Capitan onto the iMac's drive.