Inode

Inode

The inode is a data structure that describes a file system object such as a file or a directory. Unlike block addresses, inode addresses start at 1.

Starting Byte	Ending Byte	Size In Bytes	Field Description
0	1	2	Type and Permissions
2	3	2	User ID
4	7	4	Size in bytes
8	11	4	Last access time
12	15	4	Creation time
16	19	4	Last modification time
20	23	4	Deletion time
24	25	2	Group ID
26	27	2	Count of hard links (directory entries) to this inode
28	31	4	Count of disk sectors in use by this inode, not counting the actual inode structure nor directory entries linking to the inode
32	39	8
40	43	4	Direct Block Pointer 0
44	47	4	Direct Block Pointer 1
48	51	4	Direct Block Pointer 2
52	55	4	Direct Block Pointer 3
56	59	4	Direct Block Pointer 4
60	63	4	Direct Block Pointer 5
64	67	4	Direct Block Pointer 6
68	71	4	Direct Block Pointer 7
72	75	4	Direct Block Pointer 8
76	79	4	Direct Block Pointer 9
80	83	4	Direct Block Pointer 10
84	87	4	Direct Block Pointer 11
88	91	4	Singly Indirect Block Pointer
92	95	4	Doubly Indirect Block Pointer
96	99	4	Triply Indirect Block Pointer
100	119	20
120	121	2	High 16 bits of 32-bit User ID
122	123	2	High 16 bits of 32-bit Group ID
124	127	4

Inode Type and Permissions

Type Value	Type Description
0x1000	FIFO
0x2000	Character device
0x4000	Directory
0x6000	Block device
0x8000	Regular file
0xA000	Symbolic link
0xC000	Unix socket

Permission Value	Permission Description
0x001	Other - execute
0x002	Other - write
0x004	Other - read
0x008	Group - execute
0x010	Group - write
0x020	Group - read
0x040	User - execute
0x080	User - write
0x100	User - read
0x200	Sticky Bit
0x400	Set group ID
0x800	Set user ID