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
68 * filetype, recover, meta_bg, extents, 64bit, flex_bg: **yes**
69 * compression, journal_dev, mmp, ea_inode, dirdata, bg_meta_csum, largedir, inline_data: **no**
73 * has_journal, ext_attr, dir_index: **yes**
74 * dir_prealloc, imagic_inodes, resize_inode: **no**
78 * sparse_super, large_file, huge_file, gdt_csum, dir_nlink, extra_isize, metadata_csum: **yes**
79 * quota, bigalloc, btree_dir: **no**
83 * blockdev - block devices set, supported blockdev
84 * fs_test - test suite, mkfs and demo application
86 * include - header files
87 * toolchain - cmake toolchain files
88 * CMakeLists.txt - CMake config file
89 * ext_images.7z - compressed ext2/3/4 100MB images
90 * fs_test.mk - automatic tests definitions
91 * Makefile - helper makefile to generate cmake and run test suite
92 * README.md - readme file
100 Download MSYS-2: https://sourceforge.net/projects/msys2/
102 Install required packages is MSYS2 Shell package manager:
104 pacman -S make gcc cmake p7zip
109 Package installation (Debian):
111 apt-get install make gcc cmake p7zip
114 Compile & install tools
123 lwext4-generic demo application
125 Simple lwext4 library test application:
126 * load ext2/3/4 images
127 * load linux block device with ext2/3/4 part
128 * load windows volume with ext2/3/4 filesystem
129 * directory speed test
130 * file write/read speed test
132 How to use for images/blockdevices:
134 lwext4-generic -i ext_images/ext2
135 lwext4-generic -i ext_images/ext3
136 lwext4-generic -i ext_images/ext4
139 Show full option set:
141 lwext4-generic --help
147 Execute tests for 100MB unpacked images:
151 Execute tests for autogenerated 1GB images (only on Linux targets) + fsck:
155 Using lwext4-mkfs tool
157 It is possible to create ext2/3/4 partition by internal library tool.
159 Generate empty file (1GB):
161 dd if=/dev/zero of=ext_image bs=1M count=1024
163 Create ext2 partition:
165 lwext4-mkfs -i ext_image -e 2
167 Create ext3 partition:
169 lwext4-mkfs -i ext_image -e 3
171 Create ext4 partition:
173 lwext4-mkfs -i ext_image -e 4
175 Show full option set:
180 Cross compile standalone library
185 Lwext4 could be compiled for many targets. Here are an examples for 8/16/32/64 bit architectures.
186 * generic for x86 or amd64
187 * arm-none-eabi-gcc for ARM cortex-m0/m3/m4 microcontrollers
188 * avr-gcc for AVR xmega microcontrollers
189 * bfin-elf-gcc for blockfin processors
190 * msp430-gcc for msp430 microcontrollers
192 Library has been tested only for generic (amd64) & ARM Cortex M architectures.
193 For other targets compilation passes (with warnings somewhere) but tests are
194 not done yet. Lwext4 code is written with endianes respect. Big endian
195 behavior also hasn't been tested yet.
197 Build avrxmega7 library:
205 Build cortex-m0 library:
213 Build cortex-m3 library:
221 Build cortex-m4 library: