Booting fails with disk0s2: I/O error and EXITED WITH SIGNAL 8

Please tell us your iMac model (or what in year it was new) and your Mac OSX version. iMacs have been in continuous production since 1998 and in four broad families and hundreds of variants. Troubleshooting recommendations can vary with model.

That's a start, but there is no "G6", so it could be Intel powered. Although the last G5s and the first Intel iMacs look almost identical externally, there are major internal differences between troubleshooting a PowerPC (G3, G4, or G5) Mac and the newer intel Macs, so let's pin it down farther,

As the computer apparently does not start, we can go from the serial number which I believe is on a sticker on the underside of the "foot" upon which the computer stands. Get the serial number and enter it into this Apple web page:

https://selfsolve.apple.com/agreementWarrantyDynamic.do

It should return a model designation. If this computer is too old (possible) for this to work, you have the same function on this external site:

http://www.everymac.com/ultimate-mac-lookup/

We are looking for the model description ( ex., "iMac G5 17-inch iSight" or "iMac 2006 17-inch") rather than a model number but, if all you get is a model number (starts with "A" or "M"), we can work with that.

As it's Christmas Eve and we have a house full of people, I may not be able to get back here right away but I will try to check in within a couple of hours.

Allan

Did you notice that the mac could not verify the filesystem. It found errors. It does try to fix the problem if it can. You could try DiskWarrior for a more expensive and extensive repair. There are no guarantees it will work.

I select a OXS Installation Disc, it boots on the internal drive, no matter what I do.

I'm concerned a out this.

Try this:

Start with DVD in drive. Power off your machine. Hold down the option key when you poweron. This will bring up the startup manager. Click on cd/dvd. Click on right arrow. ( I think that this is your best approach. )

Your statup manager may be slightly different, but this is the idea.

http://docs.info.apple.com/article.html?artnum=106178

I do not think you can get into single user mode with a firmware password. Without a firmware password, you should be able to get into startup manager. You have the correct dvd?

Robert

Article 106178 has been replaced, see this tip:

Knowledgebase links of the info.apple.com format no longer work

How to choose a startup disk on your Mac - Apple Support

Note, the Darwin version is from 2011. It must be an Intel Mac. No Darwin version newer than August 27, 2009 will run on a PowerPC Mac.

Startup Manager on Intel looks different:

Use the Option key, when possible instead of 'C' key to boot discs

I'm in agreement with my prior post.

There are other sites that have info on vintage machines. Info from:

http://www.appleserialnumberinfo.com/Desktop/index.php