How to use third party file systems on macOS


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Apple's macOS operating system allows you to mount and access storage volumes used by other operating systems on your desktop. Here's how to get started.

Your Mac can read audio CDs or most USB drives pre-formatted for Windows. The Mac has supported foreign file systems for decades, with a plug-in architecture that allows macOS to mount, read, and, in some cases, write to and from storage volumes formatted for other computers.

It also supports mounting some remote network volumes on the desktop as if they were disks.

All of this is possible thanks to Mac external file system plug-ins. Each plugin sits between native macOS file I/O APIs and the actual low-level device I/O code. When an I/O request is sent to a storage volume, macOS first checks the volume's format.

If it's a format that macOS natively understands, it just completes the I/O. But if the volume is formatted with a file system that macOS does not natively understand, it looks for an external file system (FFS) plug-in and, if it finds a match, redirects the I/O request to the FFS plug-in.

The plug-in code then takes over and processes the I/O request, ordering data into or out of the storage volume as requested.

Any number of file systems can be supported on macOS as long as there is a corresponding plug-in for each external volume format. In fact, macOS doesn't even need to know many details about — each FFS plugin does most of the work. macOS simply says “Here, read the data in this location and return it to me” or “Here, write this data and return to me with confirmation.”

This plug-in architecture makes it easy to expand FFS support in the future to support more formats and allows file systems to be upgraded independent of the operating system as a whole. Brilliant.

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Built-in FFS support

Starting with macOS 13 Ventura, macOS supports most Windows FAT formats, Windows NTFS read-only volumes, ISO 9660 CD format, DVD (UDF), Blu-Ray, other ISO optical standards, and decade-old older Mac OS formats , such as HFS Plus. used for macOS Extended.

Plugins for macOS FFS are located in two places on the boot drive:

  • /System/Library/Filesystems
  • /Library/Filesystems< /li >

    If you look inside these two folders, you'll see packages of code, each with a “.fs” file extension. Removing or installing a new, valid .fs package in any of these locations and then logging out and back in will give macOS access to all volumes that the new .fs package is designed to support.

    In general, you don't want to touch anything in /System/Library/Filesystems. This directory is used by the system, and changing it can lead to errors, crashes, or even data corruption.

    Any new FFS plugins you add should be added to /Library/Filesystems.

    Network File Systems

    Also inside both folders there is a subfolder named “NetFSPlugins”. This folder contains .fs packages that know how to mount, mount, unmount and read+write to a remote network server as if it were a network volume on the desktop.

    If you look in /System/Library/Filesystems/NetFSPlugins, for example, you'll find .fs packages for FTP, HTTP, Windows SMB shares, NFS, WebDAV, and more. Each of the .fs network packages knows how to remotely interact with these network protocols to perform I/O operations.

    Each network .fs package also mimics a real file system and “tricks” the Finder into thinking that each remote resource is a storage device so it can mount them as volumes on the Finder desktop. Once connected, you can double-click them, drag files to and from the remote location, drag files to the Trash, unmount them, and perform other Finder tasks seamlessly—all over the network.

    Some FFS plugins may not support all Finder tasks other than basic I/O, but many do. Some, for example, may prevent you from setting Finder tags, changing permissions, or displaying full information in Finder Get Info windows. Read-only .fs packages will mount, read, and unmount FFS volumes, but you won't be able to write to them.

    Because most .fs packages work at the OS kernel level, they must be very well written, tested, and reliable. One small mistake in the .fs package can corrupt the entire volume and make it unusable for mounting and restoring.

    Apple has done a wonderful job of making the FFS mechanism in macOS extremely reliable, and almost no data corruption issues have been reported.

    Third Party FFS Bundles

    The plug-in system opened up opportunities for third parties to write and release their own FFS solutions, and some of them have done just that. Some of them are free, some you have to pay for. These include, but are not limited to:

    • Tuxera NTFS for Mac is a complete NTFS FFS plug-in for reading and writing to Windows NTFS volumes.
    • NTFS by Paragon for Mac.
    • OpenAFS
    • OpenZFS
    • ProFuse is no longer supported – support for Apple II ProDOS format disks since the 1980s.

    Most of them include an installer that you can run to automatically install the .fs packages to the correct location. Some do not include installers.

    MacFUSE: User Level Filesystems

    In 2009, Amit Singh released MacFUSE, a user space extension for Mac files. The idea behind MacFUSE is that once installed, third-party filesystems can now be written to in user space instead of in the kernel.

    Theoretically, this greatly simplifies writing and testing them, since a bug in the MacFUSE file system will not bring the entire system to a halt, as a buggy FFS at the kernel level can.

    Many macOS FFS MacFUSE plugins followed, including one for Google File System (GFS), Linux (optional) and more. MacFUSE hasn't been updated in over 10 years, but still works with most FFS plugins in macOS 13 Ventura on Intel-based computers. Your mileage may vary.

    One FUSE-based FFS for macOS is TabFS by Omar Rizwan. Once installed, TabFS allows you to mount all open browser tabs to a folder on your desktop and access them from there.

    Once you know how foreign filesystems work on macOS, as long as you can find the correct system for the third-party volume format you want to mount and access, everything else will be hassle-free.< /p>

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