This is a test implementation of ext4 in pure-Python, not supporting all ext4 features. The aim is not to write in the ext4 file system, but only to read some (and not all) structure into it. The supported features are those required to implement these standard commands:
ls [-a] [-l] <path>cat <path>
These implementations are in the two scripts ls.py and cat.py. To get rid
of difficulties of mounting the file system into the kernel, the project
directly read the block device (/dev/sdXY). This requires the root rights.
You can safely provide your own ext4 file system, as it is never mounted
read-write, but only read-only. You should provide the device block path while
running scripts:
sudo python ls.py /dev/sdXY [-a] [-l] <path>sudo python cat.py /dev/sdXY <path>
You may compare with output of the real ls and cat on a mounted file system.
For the supported features, the output should be the same.
Another script, called dump.py, allows raw dump of some structures
(superblock, block group descriptors,…). Useful for debugging.
Based on the wiki of kernel.org: [https://www.kernel.org/doc/html/latest/filesystems/ext4/index.html]. Tested on some real ext4 filesystem (e.g. the true root filesystem on which development were done). Based on that documentation, we implemented:
- Read the superblock
- Checksum is checked (if they are computed in the filesystem!)
- Read block group descriptors
- Checksum is checked
- Read inode table
- Read file content
- direct block addressing
- extent tree of depth 1
- Read directory entries
- Linear directories