Ext2 compression extension

The Ext2 Compression Extension (E2compr) is a powerful patch that can seamlessly compress and decompress files on-the-fly within the ext2 filesystem. This patch can compress only regular files, excluding the administrative data such as the superblock, inodes, and directory files for safety reasons. E2compr allows read and write operations to access compressed blocks.

The compression algorithm and cluster size can be specified on a per-file basis, and directories can also be marked for compression. In case a directory is marked for compression, every newly created file in the directory will automatically inherit the directory's compression flag, algorithm, and cluster size. E2compr is not a new filesystem but an ext2 patch built to support the EXT2_COMPR_FL flag, which can read or write existing ext2 filesystems without making a new partition.

Usage of E2compr is relatively easy. A file is compressed with the command `chattr c filename', and decompressed with the command `chattr-c filename'. Similarly, directories can be compressed with `chattr c' and decompressed with `chattr -c'. To check if a file should be compressed, use `lsattr' to see what compression algorithm and cluster size will be used. The e2ratio command can show how much disk space the compressed form takes compared to the uncompressed form. For directories, e2ratio finds the disk usage of the entire directory tree, whereas `lsattr-u' only shows the space taken by the directory file.

One thing to note about E2compr is that it does not compress administrative data for safety reasons. Overall, E2compr is an excellent patch that can coexist with compressed and uncompressed files on the ext2 partitions, making it an excellent choice for those looking to compress files in the ext2 filesystem.