In contrast, file-system–wide operations are implemented using VFS calls. Examples include VOP_OPEN to open a file and VOP_READ to read file contents. VOP calls are used for operations on individual files or directories (such as open, close, read, or write). Within a file system, operations on specific files and directories are implemented via vnodes and VOP (vnode operation) calls. There is a unique vnode allocated for each active file or folder, including the root. In OS X, the vnode structure provides the internal representation of a file or directory (folder). If you want to support a new volume format or networking protocol, you’ll need to write a file-system kernel extension. Examples of file systems that are not currently supported in OS X but that you may wish to add to the system include the Andrew file system (AFS) and the Reiser file system ( ReiserFS). These include such characteristics as Finder Info, file ID access, and aliases.īy using the OS X Virtual File System (VFS) capability and writing kernel extensions, you can add support for other file systems.
#Hfs file system overview mac os#
The Carbon application environment mimics many expected behaviors of Mac OS Extended format on top of both UFS and NFS. NFS provides access to network servers as if they were locally mounted file systems. Other file systems can also be mounted, allowing users to gain access to additional volume formats and features. That is, OS X can boot from and mount a volume of any of these types and use it as the primary, or root, file system. OS X currently can boot and “root” from an HFS+, UFS, ISO, NFS, or UDF volume. In contrast, Mac OS Extended Format is not case-sensitive (but is case-preserving). UFS provides case sensitivity and other characteristics that may be expected by BSD commands. The Mac OS Extended format provides many of the same characteristics as Mac OS Standard format but adds additional support for modern features such as file permissions, longer filenames, Unicode, both hard and symbolic links, and larger disk sizes. OS X cannot boot from these file systems, nor does the Mac OS Standard format provide some of the information required by OS X. Support is also included for reading the older, Mac OS Standard format ( HFS) file-system type however, you should not plan to format new volumes using Mac OS Standard format.
#Hfs file system overview iso#
These include Mac OS Extended format ( HFS+), the BSD standard file system format ( UFS), NFS (an industry standard for networked file systems), ISO 9660 (used for CD-ROM), MS-DOS, SMB (Windows file sharing standard), AFP (Mac OS file sharing), and UDF. OS X provides “out-of-the-box” support for several different file systems.
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