Addressing failing software installations in OS X
Sometimes software installations may fail in OS X, which can be caused by faults with the installation media or by improper system set-ups.
On rare occurances, people may find that installing software from an installation CD, DVD, or downloaded installer may result in a failed installation. Sometimes the install will either hang or crash, but other times an error may be presented. Some of these errors can be cryptic-looking codes, but others might be more general such as the installer stating the software "cannot be installed on the system, please contact the developer."
The first thing to do is to double-check the system requirements for the software. While many installers will run a program that ensures the hardware and OS version meet the minimum requirements, others may not have this feature and will rely on you to have the supported system requirements. Usually, as long as the OS version and CPU architectures meet the software's requirements, then the software will run, but sometimes there are other hardware requirements that need to be met.
In addition to system requirements, the OS will also need to be able to accept the installed files. Sometimes permissions problems on the boot drive can result in a failed installation if the installer cannot write to specific folders (e.g., the Fonts or Applications directories). In this case, running a permissions fix on the boot drive with Disk Utility is an easy way to check for and address possible file system access problems. An alternative to this is to perform ato clear caches and reset other temporary items on the disk in addition to fixing permissions.
Permissions issues might also extend to the application-specific directories for the program being installed, which might be especially true for program updaters. Sometimes folders that an application or its installer creates will not be checked in a permissions-fix routine, and if there are access problems with these files or folders then application updaters may fail. This kind of error can happen after restoring a system or migrating to a new system. In this case, try first uninstalling and reinstalling the software before updating.
While system requirements and set-up might sometimes be the cause of installation problems, in many cases the problem happens because of faults with the installation media itself. In the case of physical media, you might have scratches or dirt on the installation discs, in which case inspecting and cleaning it with a soft rag might be helpful.
In addition, sometimes specific media might not be readable by the optical drive or even the system installer programs. In this case, you can try creating a disk image of the media using Disk Utility and then mounting the image or re-burning it to another disc. Since the problem may be with how the current system is reading the optical disc, you might try using a second computer to duplicate the disc or create the image file.
The last option is with errors in downloaded media. Many programs these days are distributed in a packaged format such as a zip file or disk image, and if there are problems with the downloaded file then the installer may not run correctly, if at all. Try re-downloading the file and seeing if a fresh copy works. If the developers provide a check-sum (usually an "md5" or "sha" check-sum) for the file you can check it in the terminal by typing "md5" or "shasum" followed by a space, dragging the downloaded file to the terminal window, and then pressing enter. The resulting string of characters should match that given by the developer, but if not then it is likely the file has become corrupted somewhere along the line.