3.4. Checking the inode state An individual inode is not as likely to be corrupted as the allocation information. However, because of the great number of active inodes, a few of the inodes are usually corrupted. The list of inodes in the ﬁle system is checked sequentially starting with inode 2 (inode 0 marks unused inodes; inode 1 is saved for future generations) and progressing through the last inode in the ﬁle system. The state of each inode is checked for inconsistencies involving format and type, link count, duplicate blocks, bad blocks, and inode size. Each inode contains a mode word. This mode word describes the type and state of the inode. Inodes must be one of six types regular inode, directory inode, symbolic link inode, special block inode, special character inode, or socket inode. Inodes maybe found in one of three allocation states unallocated, allocated, and neither unallocated nor allocated. This last state suggests an incorrectly formated inode. An inode can get in this state if bad data is written into the inode list. The only possible corrective action is for fsck is to clear the inode.