| .. SPDX-License-Identifier: GPL-2.0 |
| |
| Special inodes |
| -------------- |
| |
| ext4 reserves some inode for special features, as follows: |
| |
| .. list-table:: |
| :widths: 6 70 |
| :header-rows: 1 |
| |
| * - inode Number |
| - Purpose |
| * - 0 |
| - Doesn't exist; there is no inode 0. |
| * - 1 |
| - List of defective blocks. |
| * - 2 |
| - Root directory. |
| * - 3 |
| - User quota. |
| * - 4 |
| - Group quota. |
| * - 5 |
| - Boot loader. |
| * - 6 |
| - Undelete directory. |
| * - 7 |
| - Reserved group descriptors inode. (“resize inode”) |
| * - 8 |
| - Journal inode. |
| * - 9 |
| - The “exclude” inode, for snapshots(?) |
| * - 10 |
| - Replica inode, used for some non-upstream feature? |
| * - 11 |
| - Traditional first non-reserved inode. Usually this is the lost+found directory. See s\_first\_ino in the superblock. |
| |
| Note that there are also some inodes allocated from non-reserved inode numbers |
| for other filesystem features which are not referenced from standard directory |
| hierarchy. These are generally reference from the superblock. They are: |
| |
| .. list-table:: |
| :widths: 20 50 |
| :header-rows: 1 |
| |
| * - Superblock field |
| - Description |
| |
| * - s\_lpf\_ino |
| - Inode number of lost+found directory. |
| * - s\_prj\_quota\_inum |
| - Inode number of quota file tracking project quotas |
| * - s\_orphan\_file\_inum |
| - Inode number of file tracking orphan inodes. |
