OS X Mavericks offers a number of new features and enhancements to OS X, both in features you might use as well as under-the-hood optimizations; however, in order to take advantage of these you must first successfully install the OS, and this is where a few users have run into issues.
In some cases, people attempting to install the OS are running into a problem where the Mavericks installer claims the hard disk is damaged and needs to be repaired. Other times Mavericks might be hung up downloading from the Mac App Store, or never complete its final installation steps.
If these, or similar issues are preventing your installation from proceeding, then you can likely overcome them with a few easy steps.
- Stuck download
If your download from the Mac App Store appears to be stuck and no longer progressing, then you can clear it by quitting the App Store, restarting your system, and then re-trying the download at a later time. Since Mavericks is free, at least initially Apple's servers may be a bit taxed, so in some cases connections may time out or otherwise stop working. Re-downloading at a later time may clear the issue up.
- Hard disk errors found
A second issue may occur when the OS X installer finds fault with your hard drive and will not install. In these cases you can usually clear the problem by rebooting to the OS X recovery partition by holding Command-R immediately after hearing the boot chime at startup. Once the recovery partition has loaded, you can open Disk Utility and use it to run a disk repair routine on your main boot drive. After any found errors have been fixed, you can then reboot normally and try the installation again.
- Hung up installation
If you are able to run the installer but the progress has halted, at first do not try to interrupt it. Sometimes OS X installations may hit a small snag or two that take a while to overcome, so initially wait it out. If the progress has not advanced after an hour, then it is time to try fixing the issue. If you are still in your main OS X installation before the system reboots to install Mavericks, then you can attempt to quit the Mavericks installer or force-quit it. Following this, reboot the system and try the installation again (open the installer in the Applications folder, or re-download it from the Mac App Store).
If the system has restarted and you are at the Mavericks installation progress with no OS running in the background, then your only option is to force-restart the system by holding the power button. This unfortunately can be risky, but in most cases should allow the system to reboot normally in the prior version of OS X. If so, then try running some general maintenance routines, and optionally download and re-apply the latest "Combo" updater for your version of OS X, before attempting the installation again.
Lastly, if you reset the system and you cannot boot to OS X again, then you will have to reinstall OS X from the recovery partition. To do this, reboot with the Command-R keys held down and then either restore your system from a backup, or use the OS X installer tool to reinstall the OS (your data and program installations should not be affected). When finished, you can then re-try the Mavericks installation.