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