1 [![Build Status](https://travis-ci.org/gkostka/lwext4.svg)](https://travis-ci.org/gkostka/lwext4)
3 ![lwext4](https://cloud.githubusercontent.com/assets/8606098/11697327/68306d88-9eb9-11e5-8807-81a2887f077e.png)
8 The main goal of the lwext4 project is to provide ext2/3/4 filesystem for microcontrollers. It may be an interesting alternative for traditional MCU filesystem libraries (mostly based on FAT32). Library has some cool and unique features in microcontrollers world:
9 - directory indexing - fast file find and list operations
10 - extents - fast big file truncate
11 - journaling transactions & recovery - power loss resistance
13 Lwext4 is an excellent choice for SD/MMC card, USB flash drive or other block based memory device. However it is not good for flash memory–based storage devices.
15 Feel free to contact me:
16 kostka.grzegorz@gmail.com
21 The most of the source code of lwext4 was taken from HelenOS:
24 Some features are based on FreeBSD and Linux implementations.
26 KaHo Ng (https://github.com/ngkaho1234):
27 * advanced extents implementation
29 * metadata checksum support
30 * journal recovery & transactions
31 * many bugfixes & improvements
33 Lwext4 could be used also as fuse internals. Here is a nice project which uses lwext4 as a filesystem base:
34 * https://github.com/ngkaho1234/fuse-lwext4
39 * filetypes: regular, directories, softlinks
40 * support for hardlinks
41 * multiple blocksize supported: 1KB, 2KB, 4KB ... 64KB
42 * little/big endian architectures supported
43 * multiple configurations (ext2/ext3/ext4)
44 * only C standard library dependency
45 * various CPU architectures supported (x86/64, cortex-mX, msp430 ...)
46 * small memory footprint
47 * flexible configurations
52 Advanced ext4 filesystem features, like extents or journaling require some memory.
53 However most of the memory expensive features could be disabled at compile time.
54 Here is a brief summary for cortex-m4 processor:
56 * .text: 20KB - only ext2 fs support , 50KB - full ext4 fs feature set
57 * .data: 8KB - minimum 8 x 1KB block cache, 12KB - when journaling and extents are enabled
58 * .stack: 2KB - is enough (not measured precisely)
60 Blocks are allocated dynamically. Previous versions of library could work without
61 malloc but from 1.0.0 dynamic memory allocation is required. However, block cache
62 should not allocate more than CONFIG_BLOCK_DEV CACHE_SIZE.
64 Supported ext2/3/4 features
66 Features incompatible:
87 * has_journal: yes (in progress)
108 * blockdev - block devices set, supported blockdev
109 * fs_test - test suite, mkfs and demo application
111 * include - header files
112 * toolchain - cmake toolchain files
113 * CMakeLists.txt - CMake config file
114 * ext_images.7z - compressed ext2/3/4 100MB images
115 * fs_test.mk - automatic tests definitions
116 * Makefile - helper makefile to generate cmake and run test suite
117 * README.md - readme file
125 Download MSYS-2: https://sourceforge.net/projects/msys2/
127 Install required packages is MSYS2 Shell package manager:
129 pacman -S make gcc cmake p7zip
134 Package installation (Debian):
136 apt-get install make gcc cmake p7zip
139 Compile & install tools
148 lwext4-generic demo application
150 Simple lwext4 library test application:
151 * load ext2/3/4 images
152 * load linux block device with ext2/3/4 part
153 * load windows volume with ext2/3/4 filesystem
154 * directory speed test
155 * file write/read speed test
157 How to use for images/blockdevices:
159 lwext4-generic -i ext_images/ext2
160 lwext4-generic -i ext_images/ext3
161 lwext4-generic -i ext_images/ext4
164 Show full option set:
166 lwext4-generic --help
172 Execute tests for 100MB unpacked images:
176 Execute tests for autogenerated 1GB images (only on Linux targets) + fsck:
180 Using lwext4-mkfs tool
182 It is possible to create ext2/3/4 partition by internal library tool.
184 Generate empty file (1GB):
186 dd if=/dev/zero of=ext_image bs=1M count=1024
188 Create ext2 partition:
190 lwext4-mkfs -i ext_image -e 2
192 Create ext3 partition:
194 lwext4-mkfs -i ext_image -e 3
196 Create ext4 partition:
198 lwext4-mkfs -i ext_image -e 4
200 Show full option set:
205 Cross compile standalone library
210 Lwext4 could be compiled for many targets. Here are an examples for 8/16/32/64 bit architectures.
211 * generic for x86 or amd64
212 * arm-none-eabi-gcc for ARM cortex-m0/m3/m4 microcontrollers
213 * avr-gcc for AVR xmega microcontrollers
214 * bfin-elf-gcc for blockfin processors
215 * msp430-gcc for msp430 microcontrollers
217 Library has been tested only for generic (amd64) & ARM Cortex M architectures.
218 For other targets compilation passes (with warnings somewhere) but tests are
219 not done yet. Lwext4 code is written with endianes respect. Big endian
220 behavior also hasn't been tested yet.
230 Build avrxmega7 library:
238 Build cortex-m0 library:
246 Build cortex-m3 library:
254 Build cortex-m4 library: