#ext4 #tools

ext4

Read information from EXT4 filesystem images

12 releases (7 breaking)

0.8.0 Jan 11, 2021
0.7.0 Oct 27, 2019
0.6.0 Jun 27, 2018
0.5.0 Dec 10, 2017
0.1.1 Jun 3, 2017

#71 in Filesystem

MIT license

165KB
1.5K SLoC

Status

Build status

ext4-rs can extract the basic stat information, directory listings, and file content from real images generated by other tools, and by the Linux kernel.

This operates directly on partitions. To read actual disc images, probably need to handle partition tables. This can be accomplished with the bootsector crate.

All basic file types are represented: files, directories, symlinks, char and block devices, fifos and sockets. Hard links are not a type of thing that makes sense: the item is just in multiple directories.

Practical problems

  • No support for extended flags (e.g. immutable, append-only).
  • Probably contains overflows and fencepost errors, many of which Rust will translate to panics for you. At least, in debug mode.

Non-goals

This is not a filesystem driver. It does not support efficiently modifying real filesystems. Currently, it doesn't support modifying anything at all, but that may change.

I'm not especially interested in resource-constrained platforms: memory and IO are not used efficiently.

Changelog

  • 0.7.0: use rust 1.34 features to remove cast dependency
  • 0.6.0: use failure for error handling
  • 0.5.0: update bitflags for associated constants, and rename some public constants.
  • 0.4.1: fix for an infinite loop parsing directory entries

MSRV

Rust 1.34 (TryFrom) is supported, and checked by Travis. Updating this is a semver bump.

Development

Tests

Some of the tests read generated image files. These images are not directly checked into git, and will be unpacked by build.rs. These files are apparently very large, but should take very little space. This requires a decent tar to be on the path.

These test assets can be rebuilt (on Linux, with root) by running ./extract-test-data --refresh.

License note

The code is licensed under the super-permissive MIT license.

However, a number of struct and bitfield definitions, and some maths expressions, are lifted directly from the Linux, or e2fsprogs, source code. These code-bases are under the GPLv2. I believe this to be fair use: these places are the documentation, and only interface definitions have been extracted, no code. I leave the final decision to you.

Thanks

This would have been practically impossible without the work a Djwong has done on the ext4 disk layout page on the kernel wiki. I believe this person is Darrick Wong. Thanks, man.

Dependencies

~0.6–1.1MB
~25K SLoC