How does the Apple file system work


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In a file system, data of a computer that has been leaked from outside by whoever is organized in the form of files and directories. The file system itself is an organization and access system for this data. The access routines to the file system are part of the operating system. The operating system itself is also stored in a file system.

A file system is understood to mean both the structurehow data is stored on a medium filestore), as well as the Regulationhow this is to be done (this takes place in the driver of the system).

The MacOSX file system is a mixture of file systems from older Mac operating systems and has inherited the concept of a global namespace from Unix, i.e. all file paths have a common root known as the top directory "/" from the Unix world. If you search in the Mac OS X file system using the terminal, you will find directories from a BSD Unix as well as Apple-specific directories.

Directory as the Finder showsThe same directory expanded and original as you can see in the BSD substructure via the terminal

File systems are mounted on a specific directory (mounted, from English. mount). A directory that suffers this fate is called mount point. In Mac OS X, a separate directory is created under / Volumes / for each additional file system that is needed and is saved as mount point used. With the command (without parameters) you can get an overview of the current 'mounts' in the terminal.

File systems exist for a variety of purposes. In addition to the most common, namely data storage on a partition on a hard drive, there are file systems for certain removable media (e.g. CD-ROMs and DVDs) or the iPod. In addition, there are file systems that store their raw data on files within another file instead of on partitions (this is exactly what happens with DiskImages), or the data just retained in memory and cannot be retained beyond a restart.

1.1 Other types of file systems

  • More partitions on the hard drives
  • Hand-mounted disk images
  • Via command -> mounted network file systems
  • Apple DOS (first Apple file system)
  • Apple SOS
  • Apple ProDOS (file system of the late Apple II models)
  • HFS (Hierarchical File System)
  • HFS + (extension of HFS to include file names with more than 32 characters, with journaling)
  • HFSX case-sensitive variant of HFS +
  • MFS (Macintosh File System)
  • Xsan, is a SAN file system for Mac OS X that is used to consolidate very large mass storage devices over a network.
  • The Zetta ZFS meta file system. This was supposed to come with Leopard, which it didn't. ZFS is an advanced 128-bit file system with integrated volume management. It was developed by Sun Microsystems. For licensing reasons, it will probably not be integrated into an Apple operating system in the foreseeable future.

2.1 Important file systems under MacOSX

When installing the system for the first time or for the first time, you have the option of choosing between two or three types of file systems for your partitions. If you want to delete a partition with the program "Disk Utility" or "Disk Utility", you have the same choice. The most important file systems would be:

Mac OS Extended (HFS +)

This is probably the best implemented file system and also has a journaling function. It runs faster than UFS (see below). There is also the journaling variant "Mac OS Extended (Journaled)", in which the write processes on the plate Protocol (the "Journal") is kept, this should, among other things. result in less data loss in the event of a system crash. Both variants are not completely case-sensitive, i.e. they save the spelling of a file or a directory, but afterwards they can also be accessed under different spellings. Example: You create a directory with the name "Sylvia's Photos" and you can then also access it under "syLVIa'S pHoTOs". Likewise, no folder with the name "ApfelWiki" and "apfelwiki" can exist in one directory. This fact makes HFS + unusable for the usual package management systems and you should switch to UFS or HFSX in this case. If you don't shy away from the trouble, you should definitely read the man page and use "HFSX" as the file system type parameter.

If you boot the computer with another operating system (such as Linux), you can only access the data in an HFS + system with luck and only read. This may also only apply to the variant without a journal.

UFS (Unix File System)

UFS is very old in principle and actually very well understood. Other operating systems, such as FreeBSD, use modern advancements of this file system. The UFS of Mac OS X 10.3 or earlier is an implementation of the "forefather" of these further developments and is therefore very slow. UFS makes a meticulous distinction between upper and lower case and therefore works well with package management systems.

UFS is easier to access from other systems than HFS +. Even write access is supposedly possible under Linux, but this is tricky.

2.2 All file systems under Mac OS X

  • Local file systems
    • HFS, HFS +, HFSX, ISO 9660, Microsoft MS-DOS (FAT12, FAT16 and FAT32), exFAT, UDF, UFS
  • Network file systems

More file systems on Mac OS X

Many other file systems can be integrated into the operating system with the help of MacFUSE. There are, among others, NTFS access, EncFS (an encrypted file system, GmailFS, with which you can use Gmail mailboxes as file storage, SSHFS (mount drives via SSH), ZFS, various WebDAV systems and much more.

Some programs require specific file systems. This is often the case when a program has been created that is to run on multiple platforms. Then you form the greatest common denominator as far as the file system is concerned. However, this can also result in certain programs not running on unusual Mac file systems.

This applies to Civilization IV (Mac), Legion Arena (Mac), Big Bang Board Games (Mac), and all Mac file systems that are case sensitive. These programs may not run on such file systems.

  • MacFUSE for easy activation of many file systems
  • MacFusion is the graphical user interface for MacFUSE
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