Linux File System

Linux file system is stored in partition, which is a logical disk. There are 3 type of partitions in Linux - Linux, FAT32 and Linux Swap.

ext2 (Second Extended File System) is a conventional FS using inode etc. ext3 built on ext2 is a journal file system. Change to the file system (e.g. date, size, blocks used etc) are stored in a special file so recovery is possible from known journal point. It eliminate the weakness of long check time for ext2 after abnormal shutdown. ext4 is also a journal file system with larger fs and file size support.

ReiserFS is also a journal fs like ext3. Reiser4 introduced a API for system programmer to guarantee the atomicity of file system transaction. A jfs guarantee the metadata changes have been stored in the journal file so that the kernal can at least establish a consistent state of the file system. That is, if file A was reported to have 16KB before the system failure, it will be reported as having 16KB afterward in the inode. This does not mean that the file data was properly written to the file.