A disk management library than can be used to build filesystems

Clone this repo:


  1. 0c93c9d [thinfs] Add support for VfsQueryFs IOCTL by Tricia Landers · 14 days ago master
  2. 2290773 [fs] Fixes to pass runtests (fcntl, pipeline, not empty errno) by Sean Klein · 11 days ago
  3. a55c6c4 Improve fsck-related error message by Sean Klein · 5 weeks ago
  4. 32cdbe8 Remove .. from FAT by Sean Klein · 5 weeks ago
  5. a2e55f0 [rpc] Update VFS-related ioctls by Sean Klein · 6 weeks ago


Thinfs is a collection of disk managment utilities which can be used to build a filesystem.

Thinfs currently includes an implementation of:

  • FAT16 and FAT32

Download Sources

Download ThinFS sources

Thinfs should be included in the full Fuchsia checkout by default.

jiri import thinfs
jiri update


Thinfs will be built as a part of the Fuchsia build. Follow the instructions on the Fuchsia landing pages.

To build Thinfs exclusively, the “--modules” parameter can be provided to gn. This is useful if the rest of the build is broken, or if you're trying to incrementally rebuild Thinfs alone.

./packages/gn/gen.py --modules=thinfs
./buildtools/ninja -C out/debug-x86-64


Running on Fuchsia

If you have a partition (either on a hard disk or USB) which is formatted as FAT, it will be automatically detected by the Magenta kernel and mounted using thinfs under “/volume”.

If you want to manually mount a block device, use the following steps:

Use lsblk to determine which block device you'd like to mount.


Let‘s arbitrarily choose block device ‘000’. If it is formatted as FAT, you can skip to the mounting stage immediately. Otherwise, you’ll need to format it as a FAT filesystem (which, as a warning, will wipe all data present on the partition).

To format the block device:

mkfs /dev/class/block/000 fat

To mount the block device:

mount /dev/class/block/000 /mount/path/of/your/choice