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 intended to work with all kernel versions since 4.12, but testing is focused on 5.18 and above.
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.
This module is the result of reverse engineering and testing has been limited. If you make use of the write support, there is a real risk of data corruption, so mounts are read-only by default. Please report any issues that you find.
Encryption is not yet implemented even in read-only mode, and neither are fusion drives.
If you encounter any problem, the first thing you should do is run (as root):
dmesg | grep -i apfs
to see all the error messages. If that doesn't help you, please file a github issue at https://github.com/eafer/linux-apfs-rw/issues. Or send me an email if you prefer.
Note that at this point the driver has been packaged for several distros, so it may be more convenient to install it from there instead of building it yourself. The distro packages are often outdated though, so be sure to check the version.
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
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 may 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
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 |
