=========================== Apple File System for Linux

The Apple File System (APFS) is the copy-on-write filesystem currently used on all Apple devices. This module provides a degree of experimental support on Linux.

It's supposed to work with a range of kernel versions starting at 4.9 or before, but only a few of those have actually been tested. Also, kernel versions below 4.12 will be slower for some operations. If you run into any problem, please send a report to [email protected] or file a github issue at https://github.com/eafer/linux-apfs-rw/issues.

To help test write support, a set of userland tools is also under development. The git tree can be retrieved from https://github.com/eafer/apfsprogs.git.

Known limitations

This module is the result of reverse engineering and testing has been limited. If you make use of the write support, expect data corruption. Please report any issues that you find, but I can't promise a quick resolution at this stage.

Encryption is not yet implemented even in read-only mode, and neither are fusion drives.

Build

In order to build a module out-of-tree, you will first need the Linux kernel headers. Depending on your distro, you can get them by running (as root)::

# Debian/Ubuntu
apt-get install linux-headers-$(uname -r)

# Arch/Manjaro
pacman -Sy linux-headers

# RHEL/Rocky/CentOS/Fedora
yum install kernel-headers kernel-devel

Now you can just cd to the linux-apfs-rw directory and run::

make

The resulting module is the apfs.ko file. Before you can use it you must insert it into the kernel, as well as its dependencies. Again as root::

modprobe libcrc32c
insmod apfs.ko

Mount

Like all filesystems, apfs is mounted with::

mount [-o options] device dir

where device is the path to your device file or filesystem image, and dir is the mount point. The following options are accepted:

============ ================================================================= vol=n Volume number to mount. The default is volume 0.

snap=label Volume snapshot to mount (in read-only mode).

uid=n, gid=n Override on-disk inode ownership data with given uid/gid.

cknodes Verify the checksum on all metadata nodes. Right now this has a severe performance cost, so it's not recommended.

readwrite Enable the experimental write support. This will corrupt your container. ============ =================================================================

So for instance, if you want to mount volume number 2, and you want the metadata to be checked, you should run (as root)::

mount -o cknodes,vol=2 device dir

To unmount it, run::

umount dir

Credits

Originally written by Ernesto A. Fernández [email protected], with several contributions from Gabriel Krisman Bertazi [email protected], Arnaud Ferraris [email protected] and Stan Skowronek [email protected]. For attribution details see the historical git tree at https://github.com/eafer/linux-apfs.git.

Work was first based on reverse engineering done by others [1]_ [2], and later on the (very incomplete) official specification [3]. Some parts of the code imitate the ext2 module, and to a lesser degree xfs, udf, gfs2 and hfsplus.

.. [1] Hansen, K.H., Toolan, F., Decoding the APFS file system, Digital Investigation (2017), https://dx.doi.org/10.1016/j.diin.2017.07.003 .. [2] https://github.com/sgan81/apfs-fuse .. [3] https://developer.apple.com/support/apple-file-system/Apple-File-System-Reference.pdf