Scenario/Problem: You have a file without an extension, and the Finder says it cannot open the file. How do you determine the file type and its associated software?

Solution: Because you have a file without any identifying information, you must use a combination of social analysis and computer sleuthing to determine the type of file and its associated application. Social analysis should be done first, since it is easier and may provide results more quickly.

What is Social Analysis?

With social analysis, you want to determine the file type based on the circumstances in which you came to receive the file. For example, did a coworker email you the file because it relates to a current project? Did you try to download a file for a specific purpose (a disk image, an application, an MP3 file, etc.), but you are only left with an unrecognizable file? Is the file’s creation date relatively recent, or is it several years old? Where is it located on your hard drive? In a system folder, your Downloads folder, or some other location in which you typically work?

Let’s take a look at an example. Suppose you visited a sports team’s web site and looked at its upcoming schedule. The site said that you could download the schedule into iCal or Outlook, so you clicked the link, but nothing happened. A few days later, you notice there is a file in your Downloads folder called “0910homesched.” If you happen to remember that you clicked on a link would add the team’s schedule to iCal, you might believe this is the file. While such a conclusion may be difficult to draw, looking at the name of the file here provides an additional clue. Unfortunately, when you try to open the file, the Finder says it cannot find an application to open the file.

If, however, you believe this file belongs to iCal, there are two ways you can try to open the file:

  1. First, you can open the application (iCal in this example).
  2. Next, you attempt to open the file from within the application. This is typically done from the File menu, where you have a choice to Open a file (in iCal, you select Import…).
  3. Navigate to the Downloads folder and try to select your file. If it works, great! If the file does not open in the application (or if the application will not even let you select the file), try the following method.

Add a file extension to the end of the file name:

  1. You can add an extension to the file’s name to tell Mac OS X to associate the file with a particular application. How do you know what the proper extension is?
  2. Visit FileInfo or File-Extensions and search for the relevant application. FileInfo indicates that .ics is the extension for an iCalendar file and is used by Apple’s iCal. In this example, then, you would need to add .ics to the end of “0910homesched” so that the entire file reads “0910homesched.ics.”
  3. Once you have added the extension, you should be able to go back to the above method and attempt to open the file from within your application.

If neither solution above works, then the most common problems are that the file actually should be opened by a different application or is corrupt (requiring you to get a new copy). You might try repeating the steps above–in order to try a different file extension–if you believe you can draw other reasonable conclusions as to the file’s type.

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Scenario/Problem: You have a file with an extension, but the Finder says it cannot open the file, and you have no idea what kind of file it is. How do you determine the file type and its associated software?

Solution: After determining the file’s extension, you should look up the extension in an online database. Here are a few suggested sources:

  • FileInfo ( This site has a very large database of extensions. You can search by extension or browse by file type. The search results will describe the type of file and associated applications. What is nice about this site is that many file types include Mac applications, whereas most other sites include only Windows applications. Note: If a file extension page does not list any compatible Mac applications, that does not preclude such a possibility. It simply means the web site does not know if there are compatible applications.
  • File-Extensions ( This site is very similar to FileInfo, but there are two noteworthy differences. First, the file extension descriptions generally do not list Mac applications. Second, it is common for file extensions to have not only more than one application associated with it but also more than one type of file associated with. For example, while .asc is typically an ASCII text file that any old text editor can open, it can also be a 3D Studio Max scene file, which means that it could be a configuration file for a 3D movie renderer. Obviously, those are very different types of files. File-Extensions does a much better job than FileInfo of showing you all the possible file types – not just the most common ones.

Once you have used one of these resources to determine what kind of file you have, you will have to figure out which software can read the file. If FileInfo indicated that a Mac OS X application will open the file, and you already have that application, then you can try opening the file with that software. Otherwise, here are some further troubleshooting steps:

  1. If you have already been able to determine which Mac OS X software you need, then you simply need to acquire the software. If it is commercial software, you will need to purchase it online or in a store. You might, however, visit the software manufacturer’s website to see if it offers a free demo version of the software. This will allow you to verify whether the software can really open your file. You could also visit AlternativeTo to see if there is a more cost-effective solution.
  2. If the software is freeware/shareware, you likely can use MacUpdate or Version Tracker to find the software or do a Google search to find the author’s website.
  3. If you do not wish to purchase expensive software, or if FileInfo indicated any number of applications may be able to read the file, then it may be worth doing a Google search to see what other Mac users are doing to open these files. For example, if you’re trying to open a QIF file, you might search for “Mac OS X open QIF files.” You can visit Apple’s Discussions forums and search there, as well. –
  4. If neither FileInfo nor File-Extensions indicate there is a Mac-compatible application for the file, you should do a Google search, as well. Some files simply cannot be opened (or done so without much effort). For example, if you receive a Microsoft Publisher file (which may have a .pub extension), there is currently no Mac application that can read the file. You might still run a search, such as “Mac OS X how to open Microsoft Publisher files.” If the end result is that you will need to open the file in Publisher on Windows, at least you will know.


Scenario/Problem: After receiving your brand new Mac, you quickly discover that all you have are the applications Apple has installed by default. While it’s great to have apps such as Safari, iChat, and the iLife apps (iMovie, iPhoto, iDVD, iWeb, and GarageBand), where can you go to find other software for your Mac?

Solution: Beyond purchasing software at your local Apple Store, there are a number of great online resources from which you can download and install software on your Mac.

The easiest way to get software is to use Apple’s App Store. This application comes with Mac OS X 10.7 Lion and is available to Snow Leopard users who update to at least 10.6.6. Similar to the iOS App Store in iTunes, there are thousands upon thousands of commercial and free applications you can download. Note, however, that Apple does not permit the sale of any application, utility, plug-in, extension, or other enhancement that installs part of itself in the System or main Library folders. Developers who publish software under many versions of open source licenses cannot submit their applications to the App Store, either. This means that popular applications such as OpenOffice, and popular Internet plugins such as Adobe Flash or Microsoft Silverlight are not available. Luckily, there are several websites dedicated to distributing freeware, shareware, and commercial software for Mac OS X users.

  1. Mac Update ( Mac Update is an independent software site that has a huge collection of Mac OS X applications and utilities. Each application’s page provides links to the developer’s website, a download link, user reviews and star ratings, and popular software alternatives.
  2. AlternativeTo ( This is a newer site that suggests free or lower-cost alternatives to popular commercial software. It is driven by user submissions and has an extensive Mac software section.
  3. CNET ( CNET is very similar to Mac Update but has a slightly larger database of applications, as the site still maintains links to older Mac OS 9 software.

While these three sites are some of the largest ones on the Internet, there are dozens of other sites, too. Outside of Apple’s retail stores, it can be difficult to find Mac software locally. Your best bet is to check Apple’s online database of local resellers ( Otherwise, your best selection of commercial software comes from online vendors like Amazon, MacMall, and MacConnection.


Snow Leopard has the most advanced installer yet, and it is designed to help you avoid catastrophic failures during the installation process. If you lose power or your Mac crashes during the installation, the next time you boot from the Snow Leopard installation disc, it can continue from where the installation left off. If disaster strikes while installing an older version of Mac OS X, you are afforded no such luxury. Instead, your best-case scenario is to reboot from the install disc and attempt an archive and install.

To better understand why Snow Leopard does such a good job recovering from an installation failure, you need to understand what the installer is doing during the 45 minutes that you wait for the progress bar to move from the left end to the right.

Pre-Installing Packages

When you double click the “Install Mac OS X” icon from the Snow Leopard installation DVD or boot the DVD to begin the installation, the installer copies more than 175 packages of files to your hard drive in a folder called “Mac OS X Install Data.” If booted from your Mac’s hard drive, the path to these files is  /Volumes/Mac OS X Install DVD/System/Installation/Packages. You cannot see this folder from the Finder because Apple makes it invisible, but the “Packages” folder is the meat and potatoes of your install disc, containing nearly every bit of data that the installer needs to put Mac OS X on your hard drive.

If you are installing Snow Leopard via an internal DVD drive, as nearly everyone does, then your machine restarts and boots from the Snow Leopard DVD when it has finished copying the packages. If, however, you are doing a remote install (hosting the DVD on another computer), then the “Install Mac OS X” application repartitions your hard drive, creating a small, 2.25GB disk called “Install OS X.” It installs a very small version of Mac OS X onto the partition; this version is large enough to allow your Mac to boot from it and continue installing Mac OS X but not so large that you could use the partition for anything else. This way, your Mac does not have to access the remote disc once it reboots.

Normally, when you want to boot your computer from a remote DVD, you have to perform a special series of steps when first turning on your computer, which can be complicated if connecting to a password-protected AirPort network. Apple wanted to eliminate as much of this work as possible.

Installing Mac OS X Packages

Regardless of whether you start the installation from your Desktop or the install DVD, your installation continues once the installer has copied all of the software packages to your hard drive and rebooted your machine from the install disc. The packages include everything in Mac OS X, such as the Unix-based applications, the Mac OS X system files, applications and utilities, and drivers for all sorts of peripherals.

The installer places the packages, at first, in a hidden folder called .PKInstallSandbox-tmp, which is on the root level of your hard drive (the period that precedes the folder name tells Mac OS X to make the folder invisible). Inside that folder is another folder called “Root,” and this folder contains the upgraded files. Because the installer places all the files in a temporary folder, your existing files may survive a crash or power failure, since they have not yet been modified. If you have to reboot from your install DVD, Snow Leopard recognizes what happened and can continue the installation.

At the very last minute, when the installer has written all the files to the temporary folder, it deletes the “Mac OS X Install Data” folder. It then transfers all the new data to the proper folders on your hard drive, neutralizes incompatible software, and restarts your Mac.

Dealing with Incompatible Software

Snow Leopard is the first version of Mac OS X that fully supports 64-bit applications, but to do so, it must boot from a 64-bit “kernel.” If Mac OS X is your computer’s brain, then a kernel is Mac OS X’s brain. It is small, but it directs every bit of traffic coursing through your computer’s electronic veins. Until Snow Leopard, the kernel was 32-bit, even if some applications were 64-bit. Unfortunately, some applications rely on 32-bit drivers that do not place nicely with Snow Leopard’s 64-bit kernel. The relevant metaphor here is that you need to have the right body parts for the right brain; otherwise, disaster strikes.

In testing Snow Leopard, Apple found that some software was so incompatible that it could crash the entire operating system. During the Snow Leopard installation, the installer looks for this software, and if it finds it, it moves the software to a folder called “Incompatible Software” on the root level of your hard drive. You should not open this software. If you still need to use it, contact the software developer to see if it has a version compatible with Snow Leopard.

Each time you install a Snow Leopard update (10.6.1, 10.6.2, etc.), Apple installs a new list of incompatible software. If you try to open software and receive a message indicating the software is incompatible, this is because the software appears on Snow Leopard’s “blacklist,” contained in /System/Library/PrivateFrameworks/SystemMigration.framework/Versions/A/Resources/MigrationIncompatibleApplicationsList.plist and /System/Library/PrivateFrameworks/SystemMigration.framework/Versions/A/Resources/English.lproj/IncompatibleApplicationStrings.strings.

Combating Malware

One last addition to Snow Leopard is its limited ability to protect against malware (malicious software). While viruses, malware, and trojans generally have not invaded Mac OS X, there are currently less than a handful of malware files that can wreak some havoc. Snow Leopard keeps an updated list of malware in /System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/XProtect.plist. The first time you attempt to open a file you have downloaded from the Internet, Mac OS X checks to see if the file contains a known malware. If it does, it will tell you not to open the file. Instead, you should throw it away.



Installing Mac OS X from the Terminal

In order to keep the Mac OS X installation as painless and trouble-free as possible, Apple requires you to boot from the install disc in order to perform the installation. This makes sense when you want to install the software on the hard drive you already boot from because the installer overwrites or moves existing files that the computer depends on. If a file goes missing or is removed, your computer may crash. When you boot from the install disc, your computer relies on the files on the install disc to keep it up and running, meaning the installer is free to modify your hard drive.

You may want to install Mac OS X onto either an external hard drive or a secondary internal drive. Keeping a working copy of Mac OS X on another drive allows you to quickly boot a full copy of Mac OS X, which is helpful for advanced troubleshooting or routine use when your main hard drive crashes. Even though the Mac OS X installer could safely install all of its files onto this secondary drive while booted from your internal hard drive, you must still reboot your Mac from the install disc, which costs you 30-60 minutes (or more) of productivity. Luckily, there is a way to manually perform the installation, provided you are comfortable using the Terminal.

If you are installing Snow Leopard, its installer determines the best type of installation for your disk. If you are installing an older version of Mac OS X, however, you should know that you cannot perform an archive and install with this Terminal procedure. Archive and install is only possible while booted from the installation disc.
This procedure cannot overcome corrupt software or hard drive formatting that the standard installation falls prey to, so make sure you have reviewed the section What to Know Before You Install Mac OS X before proceeding.

To manually install Mac OS X, perform these steps in order:

  1. Insert the Mac OS X disc and connect your external hard drive (or ensure that you have mounted the secondary internal hard drive).
  2. Open the Terminal from the /Applications/Utilities folder.
  3. Navigate to the OS X installation folder on the install disc. While the retail versions of Mac OS X discs from 10.4-10.6 have been named “Mac OS X Install DVD,” your restore disc or install disc may have another name. Because of this, dragging the disc icon into your Terminal window is the best way to change directories with the proper name.
  4. Type the letters “cd” (without the quotes and in all lowercase), then press the space bar a single time. Next, drag the icon of your install disc onto Terminal’s window. This adds the path to your Mac OS X install disc. Your window may look something like Figure 6.10. Now press return. If you have done this correctly, you are rewarded with a blank terminal line. If done incorrectly, you receive the error, “No such file or directory.” Repeat this step in that case until you get the blank terminal line.

This Terminal window shows a properly formatted command to change the working directory to the Mac OS X Install DVD.

Next, type the line “cd System/Installation/Packages” (without the quotes but with the proper case use). Do not forget to put a space in between “cd” and “System.” Then press return. You should again receive a blank terminal line.

Finally, type “open OSInstall.mpkg” (without the quotes but with the proper case use) and press return. This should cause Installer to open and present you with the Mac OS X installation package. You can simply install Mac OS X like you would any other application, choosing the drive and options you want.

The Mac OS X Installer window is the fruit of your Terminal labor. It allows you to install Mac OS X just like you would any other application.

Preview the Files to Be Installed

Whenever you install an application (or an operating system) through the graphical installer built into Mac OS X, you can see which files the package intends to install. If you know which files are installed and where they are installed, it is easier to troubleshoot problems that occur as a direct result of the installation. To view the files, select “Show Files” from the File menu in Installer.

This window shows the very beginning of the several hundred thousand files in the Mac OS X installation package.



Solving Mac OS X Installation Errors

December 21, 2012

There are five common problems you can encounter when installing Mac OS X. Because you are booting from your installation CD, which is in a read-only format guaranteed to work with your computer (assuming the computer meets the minimum system requirements), it is not common for software to be at fault during an installation error. […]

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Mac OS X Software Installation Options

December 19, 2012

In Snow Leopard, as well as previous versions of Mac OS X, the installer has a default set of packages it installs, but there are other packages you can add. For example, Snow Leopard does not install Rosetta by default. Rosetta is the software that allows an Intel-based Mac to run software that was designed […]

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