fatprogs is FAT32 utility project by being developed from dosfstools v2.11, which is released under the last version of GPL v2 license.

fatprogs support mkdosfs, dosfsck, dosfslabel like dosfstools and additionally dosfsdump for debugging.

dosfstools is excellent project and developed and verified for long time. But, found some issues when it is applied to embedded device. In test with 4K cluster on 32G volume, checked that dosfstools uses very large memory.(80M above) So, it may be hard to use for embedded device with small resources.

Also, there is even issue of license. Many embedded companies are hesitant to use software with a GPL v3 due to it's restriction. So some utilities including dosfstools are also provided as a yocto meta layer to preserve GPL v2 license. (meta-gplv2). But their codes are very old at leat 7~10 years ago.

To resolve above issues, fatprogs is developed from dosfstools v2.11 and patches of distribution vendors based on v2.11. And found missing features through comparison of corrupted images' recovery results with serveral FAT32 tools existing in linux and Windows chkdsk utility. Also I checked published documents for fat32 specification.

After adding missing features, optimized to use less memory. Verified the MAX RSS memory was reduced by about 90% compared to latest dosfstools version(v4.2). Tested results are attached below.

Build target 'distclean' will remove all object and execution files. And 'clean' will remove all object files except execution files.

$ make [distclean | clean]

$ make
$ make install

'asan' represent building with address sanitizer library for runtime memory debugging. 'debug' build will include debug information to trace code well with tools like gdb.

$ make debug
$ make asan

fatprogs verified the cross build test only in yocto. You may should add below statement in your bb/bbappend file to build fatprogs, which refer to dosfstools bb file in meta-gplv2.

SRC_URI = "git:https://github.com/fatprogs-org/fatprogs.git;branch=main;protocol=https"

S = "${WORKDIR}/git"

CFLAGS += "-D_GNU_SOURCE -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I${S}/include"

TARGET_CC_ARCH += "${LDFLAGS}"
EXTRA_OEMAKE = "CC='${CC}' CFLAGS='${CFLAGS}' LDFAGS='${LDFLAGS}'"

do_install() {
        oe_runmake "PREFIX=${D}" "SBINDIR=${D}${base_sbindir}" \
                "MANDIR=${D}${mandir}/man8" install
}

fatprogs was tested on x86-64, aarch64. fatprogs built and tested on full 64bit on x86-64, and with -m32 option on aarch64.

test script for fatprogs are in here

Tested images deatils are described in README file above link.

One of developement goal of fatprogs was use less resources. The following result is memory usage of fatprogs and latest dosfstools, mesasured by 'time -v' command for corrupted images.

Data is average value of each corrupted images category.

fat32\_bad\_ccXX.dump     : 1G volume, 4K cluster, about 20 files
fat32\_bad\_deXX.dump     : 1G volume, 4K cluster, about 100 files
fat32\_bad\_entXX.dump    : 1G volume, 4K cluster, about 370 files
fat32\_bad\_dirtyXX.dump  : 1G volume, 4K cluster, about 100 files
fat32\_bad\_fsinfoXX.dump : 1G volume, 4K cluster
fat32\_bad\_lfnXX.dump    : 1G volume, 4K cluster, about 60 files
fat32\_bad\_volXX.dump    : 1G volume, 4K cluster

fat32\_large.dump        : 32G volume, 4K cluster, about 400 files, full
fat32\_large\_16k.dump    : 32G volume, 16K cluster, about 400 files, full

Memory Usage (unit: KB - ratio: fatprogs/dosfstools value)
+----------------------------------------------------------+
| Images                  | fatprogs  | dosfstools | ratio |
|-------------------------+-----------+------------+-------|
| fat32_bad_ccXX.dump	  | 2224      | 6361       | 35%   |
| fat32_bad_deXX.dump     | 2208      | 6363       | 35%   |
| fat32_bad_entXX.dump    | 3963      | 34519      | 12%   |
| fat32_bad_dirtyXX.dump  | 2201      | 6369       | 35%   |
| fat32_bad_fsinfoXX.dump | 1930      | 4358       | 45%   |
| fat32_bad_lfnXX.dump    | 2190      | 6308       | 35%   |
| fat32_bad_volXX.dump    | 2179      | 6287       | 35%   |
|-------------------------+-----------+------------+-------|
| fat32_large.dump        | 9944      | 100404     | 10%   |
| fat32_large_16K.dump    | 3708      | 26820      | 14%   |
+----------------------------------------------------------+

dosfstools need about 100M memory in worst case, so embedded device might not be able to handle this type of FAT32 device. Of course, fatprogs memory also need to optimize more.

Reporting issues and suggesting features for fatprogs are always welcome. License of fatprogs is GPL-2.0. So, to avoid license violation and compatibility, fatprogs can't apply code with GPL-3.0 and other license which conflict with GPL-2.0.

Somebody who contribute to fatprogs should be careful for that. You can use fosslight scanner to check license for free. (https://fosslight.org/)

• More optimization for logic of traversing file tree and memory.
• Improve build script for cross compile.
• fatprogs does not support code page.