1.. SPDX-License-Identifier: GPL-2.0 2 3Special inodes 4-------------- 5 6ext4 reserves some inode for special features, as follows: 7 8.. list-table:: 9 :widths: 6 70 10 :header-rows: 1 11 12 * - inode Number 13 - Purpose 14 * - 0 15 - Doesn't exist; there is no inode 0. 16 * - 1 17 - List of defective blocks. 18 * - 2 19 - Root directory. 20 * - 3 21 - User quota. 22 * - 4 23 - Group quota. 24 * - 5 25 - Boot loader. 26 * - 6 27 - Undelete directory. 28 * - 7 29 - Reserved group descriptors inode. (“resize inode”) 30 * - 8 31 - Journal inode. 32 * - 9 33 - The “exclude” inode, for snapshots(?) 34 * - 10 35 - Replica inode, used for some non-upstream feature? 36 * - 11 37 - Traditional first non-reserved inode. Usually this is the lost+found directory. See s_first_ino in the superblock. 38 39Note that there are also some inodes allocated from non-reserved inode numbers 40for other filesystem features which are not referenced from standard directory 41hierarchy. These are generally reference from the superblock. They are: 42 43.. list-table:: 44 :widths: 20 50 45 :header-rows: 1 46 47 * - Superblock field 48 - Description 49 50 * - s_lpf_ino 51 - Inode number of lost+found directory. 52 * - s_prj_quota_inum 53 - Inode number of quota file tracking project quotas 54 * - s_orphan_file_inum 55 - Inode number of file tracking orphan inodes. 56