mklost+found (8) - Linux Man Pages
mklost+found: create a lost+found directory on a mounted Linux
mklost+found - create a lost+found directory on a mounted Linux second extended file system
DESCRIPTIONmklost+found is used to create a lost+found directory in the current working directory on a Linux second extended file system. There is normally a lost+found directory in the root directory of each filesystem.
mklost+found pre-allocates disk blocks to the lost+found directory so that when e2fsck(8) is being run to recover a filesystem, it does not need to allocate blocks in the filesystem to store a large number of unlinked files. This ensures that e2fsck will not have to allocate data blocks in the filesystem during recovery.