Mac OS X file attributes and permissions


Mac OS X uses a unique file system, the Mac OS Extended format, that provides both perceived simplicity and enhanced metadata attributes. These file system features are responsible for the simplification of the Mac OS X file structure. A prominent example of this simplification is that an entire application can be represented as a single icon to the user in the Finder. The enhanced metadata attributes make advanced technologies such as

Spotlight and Time Machine possible.

The downside to these file system features is the increased complexity of the underlying file system. This complexity affects both compatibility and deployment practices. In this section, you will briefly explore the unique file elements used in Mac OS X and why you need to use file containers to deploy these items.

Unique File Elements

The Mac OS Extended file system uses several unique file elements to hide complexity from the user: file attributes, resource forks, bundles, and packages. These file elements need special attention when using deployment tools.

File Attributes

Every file and folder on a Mac OS Extended volume has additional file attributes that are not immediately visible to the user but are an essential part of the file system. These attributes include creation date, modification date, ownership, permissions, access control lists, Spotlight information, Finder labels, and legacy file type information. They also includefile system flags, which are used to identify special file types such as aliases and locked files. Some of these attributes are accessed from the Get Infowindow of the Finder.

Other file systems have similar file attributes and, in general, offer support for common attributes such as ownership and permissions. However, these attributes can change or even be lost when files are copied using traditional methods. Even when items are copied between Mac OS X systems, file ownership is usually modified to match the account of the user who is performing the operation. When files are transferred to third-party file systems that don’t support all of the attributes of the Mac OS Extended file system, unsupported attributes are simply stripped away.

Resource Forks

Resource forks have a long history in the Macintosh operating system, dating back to the original Mac OS. To simplify the user experience, Apple created a forked file system to make complex items, such as applications, appear as a single icon, allowing multiple pieces of data to appear as a single item in the file system. For instance, a file will appear as a single item, but it will actually be composed of two separate pieces: a data fork and a resource fork. For many years, the Mac OS used forked files when working with both applications and documents. This system made the user experience simpler in most cases, but because most other operating systems don’t use a forked file system, compatibility was an issue. Only volumes formatted with the Mac OS Extended file system could properly use forked files.

However, when using Mac OS X to copy a forked file to any other third-party file system, the resource fork information will be separated and stored as a hidden file. For example, if you were to copy a forked file called Report.doc on a Windows FAT32 volume, the Mac file system would automatically split the forked file and write it as two discrete pieces on the FAT32 volume. The data fork would have the same name as the original, but the resource fork would end up in a file called ._Report.doc, which would remain hidden from the user in the Finder.

Legal Disclaimer

Our website is not responsible for the information contained by this article. Webworldarticles.com is a free articles resource thus practically any visitor can submit an article. However if you notice any copyrighted material, please contact us and we will remove the article(s) in discussion right away.


This article was sent to us by: George Zenitti at 06272010

Related Articles

1. Optimizing NetBoot Performance
The NetBoot service, and network-based system deployment in general, is among the most demanding services you can subject your network and servers to. Therefore, before s...

2. Mac OS X users manage their authorization rights
Even if you don’t want to enforce strict usage policies, you will still create accounts on Mac OS X for your users. The choices you make regarding user account types...

3. How to create simple NetBoot images
Many clients can read from the same NetBoot image, but when a client needs to write anything (such as print spools, browser caches, and other temporary files) back to its ...

4. Enabling ARD Remote Management
Apple Remote Desktop (ARD) 3 is the remote control, management, reporting, and deployment tool for Mac OS X systems. Every Mac OS X v10.5 system includes the client-side ...

5. Printers in Snow Leopard and Gutenprint
Printers come in varying shapes, sizes, and configurations. As the primary output device on your computer, the printer becomes an important tool for converting the digital...

6. The NetBoot service explained in detail
The NetBoot service is most commonly used to provide a temporary operating system. In this article you will learn how to further accelerate the system deployment process b...

7. How to create ZIP archives in Mac OS X
Pros: Mac OS X file elements are retained if encoded and decoded using the correct Mac OS X tools. Multiple items contained in a single file tha...

8. Acessing the Internet if you have Snow Leopard
Internet access refers to the ability of your computer to access the Internet, which allows you to browse web sites, check e-mail, and much more. The method by which you a...