The File Allocation Table (FAT) - filesystem originally created for use with MS-DOS (and later pre-NT Microsoft Windows). Currently a later revision of FAT (FAT32) is used for USB flash disks. It has made its way over to Linux systems and has official support in the Linux kernel.
As of August 26th, 2019 Microsoft has published the exFAT filesystem specification which means support for exFAT can be worked into the mainline Linux kernel. Kernel 5.4 includes initial staging code for exFAT support.
File systems ---> DOS/FAT/NT Filesystems ---> < > MSDOS fs support <*> VFAT (Windows-95) fs support (437) Default codepage for FAT (iso8859-1) Default iocharset for FAT [ ] Enable FAT UTF-8 option by default -*- Native language support ---> (iso8859-1) Default NLS Option <*> Codepage 437 (United States, Canada) <*> NLS ISO 8859-1 (Latin 1; Western European Languages) -*- NLS UTF-8
When planning on mounting FAT partitions, users may need to specify a
codepage= option with mount. In the example above the codepage for the United States and Canada is used, however other codepages can be enabled a necessary. Optionally, users can also set a default codepage for FAT in the kernel configuration. Be sure each codepage value which is to be used has been enabled in the kernel.
codepageoption via the mount will override the settings used in the kernel.
Default iocharset for fat to UTF-8; it is not recommended. Instead, pass the
utf8=true option when mounting FAT partitions (this requires CONFIG_NLS_UTF8 to be enabled in the kernel). For further information see mount man page or see the appropriate kernel documentation at /usr/src/linux/Documentation/filesystems/vfat.rst
The sys-fs/dosfstools package is needed for FAT userspace utilities:
emerge --ask sys-fs/dosfstools
It should be possible to mount FAT filesystems with the mount command. Resizing could be done using sys-fs/fatresize.
Slow file transfer speeds
If file transfer speeds are slow (can be viewed using iotop), ensure the filesystem is mounted with the
async filesystem option. Edit /etc/fstab (or /etc/autofs/auto.misc when using autofs) system files as needed, likely removing the
sync mount option. By default, filesystems are mounted using the
async mount option.
syncmount option inhibits slower transfer speeds than the default
asyncmount option. The
syncmount option may cause flash media life-cycle shortening also! See man mount option
If file transfer speeds are still slow, try remounting the filesystem with the
flush mount option:
mount -o remount,flush /path/to/mountpoint
Alternative operating system compatible filesystems
Try UDF filesystem using UDFTools, requiring sys-fs/udftools and Linux kernel UDF filesystem driver. Recently code was added to mkudffs for a fix for creating a mock partition increasing compatibility with Microsoft related operating systems. If using an older Linux kernel, ensure block size is set to 512 for increased compatibility. Most options are now default for compatibility, except for the required
--bootarea=mbr creating the mock partition.
mkudffs --bootarea=mbr --label=your_label /dev/device_file
Try Samsung's F2FS filesystem.
UTF-8/UTF-16 character hardware bugs
Sometimes hardware firmware bugs will occur on embedded devices (eg. car radios) when reading their required formatted FAT/FAT32 filesystems containing UTF-8 characters. A workaround is to ensure initially mounting the FAT filesystem using (current default) mount options
For short filenames,
codepage=437 is IBM-PC characters or basically ASCII. For long filenames,
iocharset=iso8859-1 specifies ASCII. The option
shortname=mixed is default, and can also try
shortname=win95 option. Of which, are all current defaults. Additionally to further remedy UTF-8/UTF-16 incompatible characters, use a loop with sed to replace all incompatible UTF-8/UTF-16 characters with an underscore or other ASCII character. (See this replace_chars.sh script.)
For reference, this bug was encountered with a Sony car radio. The MEX-GS610BT radio model would hard reset upon attempting to read a USB flash media/drive containing UTF-8/UTF-16 characters.
As mentioned previously, see /usr/src/linux/Documentation/filesystems/vfat.txt, the Linux Kernel vfat source code documentation, for further explanation on whether to use codepage, iocharset, or utf8 mount options.
Unsorted files and folders
When writing files to the FAT/FAT32 filesystem, devices used for reading the filesystem may show the files and folders as unsorted. Commonly, viewer prefer seeing files and folders sorted alphabetically. Install sys-fs/fatsort, and issue the following command:
- ExFAT — a Microsoft file system optimized for flash memory storage
- ext4 — an open source disk filesystem and most recent version of the extended series of filesystems.
- btrfs — a copy-on-write (CoW) filesystem for Linux aimed at implementing advanced features while focusing on fault tolerance, self-healing properties, and easy administration.
- removable media — any media that is easily removed from a system.
- /etc/fstab — a configuration file that defines how and where the main filesystems are to be mounted, especially at boot time.
- /usr/src/linux/Documentation/filesystems/vfat.txt - Documentation on the VFAT filesystem included with the Linux kernel sources.
- FAT filesystem and Linux - from Wikipedia
- FAT - from the Arch Linux wiki