The file system size must be larger than the number of blocks used by the superblock and the list of inodes. The number of inodes must be less than the maximum number allowed for the file system. The file system size and layout information are the most critical pieces of information for fsck. Although there is no way to actually check these sizes, because they are statically determined when the file system is created, fsck can check that the sizes are within reasonable bounds. All other file system checks require that these sizes be correct. If fsck detects corruption in the static parameters of the primary superblock, it requests the operator to specify the location of an alternate superblock.