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Ernesto A. Fernández
102 lines
3.3 KiB
Plaintext
102 lines
3.3 KiB
Plaintext
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Apple File System
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=================
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The Apple File System (APFS) is the copy-on-write filesystem currently used on
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all Apple devices. This module provides a degree of experimental support on
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Linux.
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It's supposed to work with a range of kernel versions starting at 4.9 or before,
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but only a few of those have actually been tested. If you run into any problem,
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please send a report to <linux-apfs@googlegroups.com>.
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To help test write support, a set of userland tools is also under development.
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The git tree can be retrieved from <git://github.com/eafer/apfsprogs.git>.
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Known limitations
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=================
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This module is the result of reverse engineering and testing has been limited.
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You should expect data corruption. Please report any issues that you find.
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Apple has released other versions of the filesystem to the public before the
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current one. I would not expect them to be compatible with this module at all,
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but I am open to fixing that if requested.
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Many features are not yet supported:
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o Encryption.
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o Compression, though the compressed contents of a file can be read from the
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'com.apple.decmpfs' and 'com.apple.ResourceFork' xattrs as long as they are
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under 64k.
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o Restoring to a snapshot.
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o Access control lists. This is not a priority.
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Build
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=====
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In order to build a module out-of-tree, you will first need the Linux kernel
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headers. On Debian, you can get them by running (as root):
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apt-get install linux-headers-$(uname -r)
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Now you can just cd to the linux-apfs-rw directory and run
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make
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The resulting module is the apfs.ko file. Before you can use it you must insert
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it into the kernel, as well as its dependencies. Again as root:
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modprobe libcrc32c
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insmod apfs.ko
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Mount
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=====
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Like all filesystems, apfs is mounted with
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mount [-o options] device dir
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where 'device' is the path to your device file or filesystem image, and 'dir'
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is the mount point. The following options are accepted:
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vol=n
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Volume number to mount. The default is volume 0.
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uid=n, gid=n
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Override on-disk inode ownership data with given uid/gid.
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cknodes
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Verify the checksum on all metadata nodes. Right now this has
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a severe performance cost, so it's not recommended.
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readwrite
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Enable the experimental write support. This WILL corrupt the container.
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So for instance, if you want to mount volume number 2, and you want the metadata
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to be checked, you should run (as root):
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mount -o cknodes,vol=2 device dir
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To unmount it, run
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umount dir
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Credits
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=======
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Originally written by Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>,
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with several contributions from Gabriel Krisman Bertazi <krisman@collabora.com>,
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Arnaud Ferraris <arnaud.ferraris@collabora.com> and Stan Skowronek
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<skylark@disorder.metrascale.com>. For attribution details see the historical
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git tree at <git://github.com/eafer/linux-apfs.git>.
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Work was first based on reverse engineering done by others [1][2], and later
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on the (very incomplete) official specification [3]. Some parts of the code
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imitate the ext2 module, and to a lesser degree xfs, udf, gfs2 and hfsplus.
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[1] Hansen, K.H., Toolan, F., Decoding the APFS file system, Digital
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Investigation (2017), http://dx.doi.org/10.1016/j.diin.2017.07.003
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[2] https://github.com/sgan81/apfs-fuse
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[3] https://developer.apple.com/support/apple-file-system/Apple-File-System-Reference.pdf
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