Editing Ext2 (section)

==Compression extension==
'''e2compr''' is a modification to the ext2 driver in the [[Linux kernel]] to support compression and decompression of files by the file system, without any support by user applications. e2compr is a small patch against ext2.

e2compr compresses only regular files; the administrative data (superblock, inodes, [[directory (file systems)|directory]] [[Computer file|files]], etc.) are not compressed (mainly for safety reasons). Access to compressed [[Block size (data storage and transmission)|blocks]] is provided for read and write operations. The [[compression algorithm]] and [[Cluster (file system)|cluster size]] is specified on a per-file basis. Directories can also be marked for compression, in which case every newly created file in the directory will be automatically compressed with the same cluster size and the same algorithm that was specified for the directory.

e2compr is not a new file system. It is only a patch to ext2 made to support the EXT2_COMPR_FL flag. It does not require user to make a new partition, and will continue to read or write existing ext2 file systems. One can consider it as simply a way for the read and write routines to access files that could have been created by a simple utility similar to gzip or compress. Compressed and uncompressed files coexist nicely on ext2 partitions.

The latest e2compr-branch is available for current releases of Linux 2.4, 2.6, and 3.0. The latest patch for Linux 3.0 was released in August 2011 and provides [[Symmetric multiprocessor system|multicore]] and [[High memory]] support. There are also branches for Linux 2.0 and 2.2.