Right off the bat I'll admit it was stupid to jump into trying to install Mavericks to the only partition without having taken adequate precautions (no backups or recovery disks), but unfortunately it's done. (the failed installation attempt, not the installation itself!) I'm on a mid-2011 MBP that was running Lion. I attempted to install Mavericks DP from the installer on my HD. The system rebooted and the installation started, but after 1 minute into the estimated 43 minutes for the installation to complete, I get an "Install Failed" message: "OS X could not be installed on your computer. The OS X upgrade couldn't be started because the disk Lion DP GM is damaged and can't be repaired. After your computer restarts, back up your data, erase your disk, and try installing again. Click Restart to restart your computer and try installing again." Restarting just repeats the process and the same problem recurs. I went into "Disk Utility" from the Installer's menu, and trying to verify the offending volume returns "This disk needs to be repaired. Click Repair Disk". Unfortunately the "Repair Disk" option stays greys out. Is there any way I can "revoke" the installation process (via the Terminal perhaps?) and get back to my previous set up with Lion (without losing data, obviously), so I can start over the right way this time? Any advice is appreciated.