Installing, Upgrading, Backing Up, and Restoring Mac OS X

What Happened to Disk Copy?

Disk Copy is a well-known Mac utility, a version of which has been around through many iterations of the Classic Mac OS as well as previous versions of Mac OS X (up to and including Jaguar). In Panther and later versions of Mac OS X, however, it's conspicuously absent. What happened?

In Panther, Apple took most (but not all!) of the functionality of Disk Copy and split it up into two new locations.

To create new image files or edit existing ones, you now use the Images menu in Disk Utility.

To mount image files, you simply double-click the file to launch a background application called DiskImageMounter. This program is located in /System/Library/CoreServices. If you go there, you will see that it still retains the old Disk Copy icon!

Unlike Disk Copy, DiskImageMounter gives no sign that an application has launched (for example, no icon gets added to the Dock). This streamlines the process of mounting images a bit, which I suppose is the rationale behind the change.

If you use Terminal, Panther and Tiger still include the hdiutil command, which is the Terminal equivalent of the former Disk Copy application. This provides access to all of the old Disk Copy features, even the ones not included in Disk Utility's Images menu.

See

• Running Mac OS X software from Terminal," in Chapter 10, for more on the hdiutil command.

Internet-Enabled Disk Images

Beginning with Mac OS X 10.2.3, Apple has simplified the procedure of working with downloaded disk images. For starters, .dmg files that are created as compressed (and read-only) are flat files that can be directly downloaded from the Internet. This eliminates the need to download a file as a .bin or .sit file and then expand it to a disk image—which in turn allows the user to skip the step that requires Expander.

To make things even simpler, the person who creates the disk image (.dmg) file can make it an Internet-enabled disk image. When you download an Internet-enabled disk image, some or all of the following occurs:

• The image is automatically mounted when the download is complete.
• The contents of the mounted image are copied to the user's drive—in the same location as the .dmg file itself or in a folder created at that location.
• If the mounted image contains a .pkg file, the Installer application may automatically launch and open the file, prompting you to install the software.
• The image is then unmounted, and the .dmg file is placed in the Trash.

The net result is that the user is left with the downloaded software ready to run or install—no additional steps required.

To save a .dmg file that has been moved to the Trash—for example, for archival purposes—just drag it out of the Trash before you next choose Empty Trash. Alternatively, in Tiger you can prevent these types of images from being moved to the Trash after they've been mounted via Disk Utility's preferences; select the option "Don't move Internet-enabled images to Trash."

Tip: Would you find it quicker and more convenient to access Disk Utility's Preferences via a System Preferences pane? You can do it. Just go to /System/Library/PrivateFrameworks/DiskImages.framework/Versions/A/Resources. Here you will find a file called DiskImages.prefPane. Double-click it to install it as a System Preferences pane. Done.

Note that the Internet-enabled feature is cleared after the first time the image is mounted. This means that, after retrieving a .dmg file from the Trash, if you mount the image a second time, the automated actions will not occur.

Creating an Internet-enabled disk image. The Disk Utility application currently does not include an option to create an Internet-enabled disk image. If you want to create one yourself, you must use the hdiutil command in Terminal. In particular, type the following:

hdiutil internet-enable -yes {path to disk image}/imagename.dmg

In the above command, imagename.dmg is the name of an existing read-only disk image. If you now double-click the image file, it should behave as described above.

Substitute no for yes in the above command to remove an already-present flag.

Note that this feature is dependent on the Web browser you are using. That is, it will work as described here only if your Web browser supports this feature. Obviously, Safari includes this support, and you will see it in action when downloading software. However, I have had trouble getting the above command to work when double-clicking an image file from the Finder.

Image Files That Won't Mount

Occasionally, if you double-click a .dmg file, it may open as text in a text editor or otherwise fail to open. This may happen because the file is corrupted. If you downloaded it from the Web, the solution may be to simply download it again.

More likely, however, the problem is that the Finder doesn't know what application is needed to open the file. In this case, if instead of double-clicking the file you drag it to the DiskImageMounter icon (in /System/Library/CoreServices), it should mount just fine.

If you want to fix the file so that double-clicking works, you can use the Open With section of the Get Info window for the file. Basically, you just change the selected application from whatever it is to DiskImageMounter. Then click the Change All button to apply the change to all future image files.

Inside Packages

Installer package files (as described in the main text) represent just one of several types of package files in Mac OS X. Receipt files (stored in /Library/Receipts) represent another type of package file and are very similar to Installer packages.

Most Mac OS X applications are also packages. Such files have an .app extension. The Finder hides the extension, however, so all you see is a single file called AppleWorks, as opposed to a file called AppleWorks.app—or, more properly, a folder called AppleWorks.app. The application file itself, as well as various accessory files used by the application (such as international language support), are stored within the package.

Inside the Mac OS X System folder, you will find .framework and .bundle files or folders. These are also considered packages and are covered in more detail in Chapter 4.

Viewing package contents. If you want to view the contents of a package from the Finder, simply Control-click (or right-click on a multibutton mouse) the package icon and choose Show Package Contents from the contextual menu. The same command is also accessible from the Action menu in Finder window toolbars. If that menu choice does not appear, the file is not a package.

Although the Finder is designed to see a package as a single file, other applications may play by different rules. For example, the Open and Save dialogs of some applications—especially older applications that don't understand the package concept—allow you to view a package as a folder and navigate within it. As a rule, you should not attempt to add new files to packages or delete or modify files within packages via this route unless you're confident of the consequences and specifically intend to do this (as in some hacks).

Search package contents. The Finder's Find/Search function does not search the contents of package files by default. If you want to do a volumewide search to locate an item inside any package, I recommend that you get the shareware utility Locator, which is a front end for the Unix locate command. To use it, first update the locate database (as Locator will request you to do on launch), type / (meaning the root level of the volume) in the In text box, and then type your search term in the Locate text box. Click Start, and you should find what you seek. Just remember that search terms are case sensitive (unless you check the Case Insensitive box).

To search the contents of an individual package, you can use the Show Package Contents command to enter the package and then enter the desired text in the Search field in the Finder window's toolbar. Alternatively, you can do a Finder search, but in the location bar click the Others button and then drag the package's Contents folder to the Search In list.

Another way to quickly navigate your volumes so that you can see inside packages, as well as all the normally invisible Unix directories and files, is to type file://local in your Web browser. In most browsers, this displays a list of the items at the root level of your startup volume. Each directory name is a hypertext link to the contents of that directory (assuming you have permission to view it). You can even display the contents of certain text documents via this method. However, in Safari this command simply opens a Finder window for the root level of your startup volume; thus, in Safari the command offers no advantages over using the Finder directly.

What's inside a package? If you use the Show Package Contents contextual-menu command to open a package file, the first thing you will typically see is yet another folder, called Contents. Inside most Contents folders is an Info.plist file.

The Info.plist file is a key file: It contains all of the critical information that the Finder and other system software needs to understand what the package contains and how the package's files should be treated. You can look at this .plist file (and similarly structured files) with any text editor (I recommend the free TextWrangler, from Bare Bones Software[www.barebones.com]). Even better, use the Apple Developer Tools utility called Property List Editor (covered more in Chapter 4).

Some packages also include a PkgInfo file, which contains a subset of the Info.plist data; the Finder uses it for quicker access.

If the package is an application, the top level (where the Contents folder resides) also sometimes contains an alias file to the actual executable code file, which is more deeply nested within the package.

Depending on the type of package, the Contents folder may include MacOS and MacOS Classic folders (where the actual applications are stored) and a Resources folder, which contains graphics and other accessory items, as well as information for multiple-language support (in .lprog folders).

What's inside an Installer package? Given that this chapter is about installing software, I want to note two files of particular interest that are included within Installer packages:

• Archive.bom. The filename extension .bom stands for bill of materials. This file contains the list of everything that the Installer will install; it creates the list that appears when you choose Show Files from the Installer's File menu. You may also see a matching file with the extension .bomout. This file contains essentially the same data, but in a form that can be read by any text editor, such as TextEdit, included in Mac OS X.Note: Receipt files left in the Receipts folder after an installation also contain an archive.bom file. This allows Mac OS X to check the .bom file for information as needed (such as when repairing permissions via Disk Utility).

  See

  • "Technically Speaking: Repair Disk Permissions and Receipts," in Chapter 5, for more details.
• Archive.pax.gz. The .gz and .pax extensions refer to separate compression schemes designed to reduce the size of this file, which contains all the files to be installed by the update.

  See

  • "Extracting from an expanded .pax.gz file," earlier in this chapter, for more details.

Filename extensions and packages. In most cases, adding the appropriate extension to a folder's name is enough to convert the folder to a package. For example, if you take an ordinary folder and change its name from foldername to foldername.pkg, you will get a message that says, "Are you sure you want to add the extension 'pkg' to the end of the name? If you make this change, your folder may appear as a single file." If you click the Add button, the folder will now appear as a package file and launch the Installer if you double-click it. Of course, the Installer will ultimately fail to open this pseudo-package, as the contents do not conform to what the Installer expects to find.

You can make this same package conversion using the .app extension. In this case, the folder will adopt the generic application icon. If you double-click it, it will attempt to launch but ultimately fail to do so (as your folder is not really an application).

Can you reverse this process? Yes. You can take any file with a .pkg or .app extension and remove the extension. When you do this for an .app file, for example, you will get a message that says, "Are you sure you want to remove the extension '.app'? If you make this change, your application may appear as a folder." However, you cannot typically remove the extension directly in the Finder. Doing so simply prevents the extension from appearing in the Finder; it does not actually delete the extension. To truly delete it, open the Finder's Get Info window for the file and click the disclosure triangle for Name & Extension. Delete the extension from the name as it appears here. Then click the disclosure triangle again. At this point, the message described above will appear.

Note: To be safe, I advise that you not try these tricks unless you're experimenting with files you've backed up elsewhere or don't care if they get ruined.

Bundle bits and packages. Another way the Finder determines whether a folder is treated as a package lies in something called Finder attributes (or bits). These bits determine whether a file is locked, for example. One of these bits is called the bundle bit (or package bit). Before the invention of packages (back in the Mac OS 8 days), this bit was relevant only to applications and had no effect on folders (whether on or off). Typically, the bundle bit was enabled for applications: It instructed the Finder to check the application for information about the type of documents the application creates. Starting in Mac OS 9, Apple decided to use the bundle bit with folders to indicate that a folder should really be treated as a package. Mac OS X similarly continues to use this bundle bit for folders.

Although bits are intended primarily for developer manipulation, numerous shareware utilities, such as Rainer Brockerhoff's XRay (www.brockerhoff.net/xray) and Gideon Softworks' FileXaminer (www.gideonsoftworks.com), make it possible for anyone to manipulate them. Turn the bundle bit on to indicate a package; turn it off to indicate a normal folder. In this case, enabling the bit for an ordinary folder will typically result in the folder's adopting a document icon. However, if you double-click it, the item will still open as a folder. In most cases, assuming you have any need as a troubleshooter to make these conversions, I would recommend using the name extension method rather than fiddling with the bundle/package bit.

Creating a package. Creating a functional package (one that truly operates as an installer file or an application), as opposed to one that looks like a package but does nothing, requires more than just converting a folder to a package: You must set up the contents of the package according to specific guidelines described in Apple's Mac OS X documentation for developers. Apple's PackageMaker utility (available as part of Apple's Xcode Developer software) provides a convenient graphical interface for automating most of this process. You can only use it, however, to create new package files or to open an existing package template (.pmsp or .pmsm) file. You cannot, for example, download a package file from the Internet and open the file in PackageMaker with the intention of modifying the contents. Further details on using PackageMaker exceed what you need to know for typical troubleshooting.

See

• "Technically Speaking: Repair Disk Permissions and Receipts," in Chapter 5, for related information.