Using fsck_s5 to check directory data blocks

Directories are distinguished from regular files by an entry in the mode field of the inode. Data blocks associated with a directory contain the directory entries. Directory data blocks are checked for inconsistencies involving:

• Directory inode numbers pointing to unallocated inodes. See ``Using fsck_s5 to check directory unallocated''.

• Directory inode numbers greater than the number of inodes in the filesystem. See ``Using fsck_s5 to check bad inode number''.

• Incorrect directory inode numbers for ``.'' and ``..'' directories. See ``Using fsck_s5 to check incorrect ``&.'' and ``..'' entries''.

• Directories disconnected from the filesystem. See ``Using fsck_s5 to check disconnected directories''.

Using fsck_s5 to check directory unallocated

If a directory entry inode number points to an unallocated inode, fsck can remove that directory entry. This condition occurs if the data blocks containing the directory entries are modified and written out while the inode is not yet written out.

Using fsck_s5 to check bad inode number

If a directory entry inode number is pointing beyond the end of the inode list, fsck can remove that directory entry. This condition occurs if bad data are written into a directory data block.

Using fsck_s5 to check incorrect &. and .. entries

The directory inode number entry for "." is the first entry in the directory data block. Its value is equal to the inode number for the directory data block.

The directory inode number entry for ``..'' is the second entry in the directory data block. Its value is equal to the inode number for the parent of the directory entry (or the inode number of the directory data block if the directory is the root directory). If the directory inode numbers for ``.'' and ``..'' are incorrect, fsck can replace them with the correct values.

Using fsck_s5 to check disconnected directories

The fsck program checks the general connectivity of the filesystem. If a directory is found that is not linked to the filesystem, fsck links the directory to the lost+found directory of the filesystem. (This condition can occur when inodes are written to the filesystem but the corresponding directory data blocks are not.) When a file is linked to the lost+found directory, the owner of the file must be notified.