Hi, I have a macbook pro model 2010-2011. I7 processors. I tried to update it to Yosemite. It made an error and went off. I tried to turn it on again. It loads the grey screen with the apple logo, and loads a boot bar. When it's done loading that after a couple of minutes, it just turns off automatically. I tried to back it up with an external drive with disk utility but it can't. I tried to run it in single user mode, but it cant check the osx as it says that there is some wrong values in the volume I think. And it can't repair it. It just keeps looping from that point, till I manually turns the machine off. It cannot safe boot either. I do not have another mac or an installation disc. Bit I do have an external drive. If I could just get it backed up so that I could re-install the osx. Hopefully someone can help. Thanks.