reference
https://www.zybuluo.com/harpsword/note/207478
https://blog.csdn.net/hejinjing_tom_com/article/details/52319189
http://www.cnblogs.com/zhangchaoyang/articles/1896605.html
https ://www.cnblogs.com/codestub/archive/2011/08/31/2160739.html
http://bachue.is-programmer.com/user_files/Bachue/File/Linux%200.11 file system implementation.pdf
http ://www.voidcn.com/article/p-vizxcuae-dd.html
https://blog.csdn.net/ac_dao_di/article/details/54670516
http://www.rutk1t0r.org/2016/12/22 /Linux Kernel 0-11 Completely Annotated-Come-Minix/
https://blog.csdn.net/fukai555/article/details/42060837
Prepare
Create a 128KB file named disk and format the file into the minix file system. There are 3 versions of the minix file system. The default here is version 1:
$ dd if=/dev/zero of=disk bs=1K count=128
$ mkfs.minix disk
64 inodes
128 blocks
Firstdatazone=6 (6)
Zonesize=1024
Maxsize=268966912The minimum reading and writing unit of a disk is a block. The general disk block size is 512 bytes, and the block size defined by Linux is 1024.
The above is divided into 128 1KB disk blocks;
ZoneSize >= BlockSize, here are all 1024;
the first data Zone starts from the Zone of index 6;
the maximum file size can reach 268966912.
Create several directories and text files:
$ mkdir mnt
$ mount disk -o loop -t minix mnt
.......
$ tree
mnt/
├── document
│ └── uname.txt
├── number.txt
└── text.txthexdump -C disk displays as follows:
00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 引导块1K
*
00000400 40 00 80 00 01 00 01 00 06 00 00 00 00 1c 08 10 |@...............| 超级块
00000410 8f 13 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000420 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000800 3f 00 00 00 00 00 00 00 fe ff ff ff ff ff ff ff |?...............| inode bitmap
00000810 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
*
00000c00 3f 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f8 |?...............| zone bitmap
00000c10 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
*
00001000 ed 41 e8 03 a0 00 00 00 1b 92 f3 5b e8 03 06 00 |.A.........[....| inode1
00001010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001020 b4 81 e8 03 0a 00 00 00 ec 91 f3 5b e8 01 07 00 |...........[....| inode2
00001030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001040 b4 81 e8 03 08 00 00 00 0f 92 f3 5b e8 01 08 00 |...........[....| inode3
00001050 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001060 fd 41 e8 03 60 00 00 00 35 92 f3 5b e8 02 09 00 |.A..`...5..[....| inode4
00001070 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001080 b4 81 e8 03 72 00 00 00 35 92 f3 5b e8 01 0a 00 |....r...5..[....| inode5
00001090 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00001800 01 00 2e 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| ZONE 6
00001810 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001820 01 00 2e 2e 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001830 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001840 02 00 6e 75 6d 62 65 72 2e 74 78 74 00 00 00 00 |..number.txt....|
00001850 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001860 03 00 74 65 78 74 2e 74 78 74 00 00 00 00 00 00 |..text.txt......|
00001870 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001880 04 00 64 6f 63 75 6d 65 6e 74 00 00 00 00 00 00 |..document......|
00001890 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00001c00 31 32 33 34 35 36 37 38 39 0a 00 00 00 00 00 00 |123456789.......| ZONE7
00001c10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00002000 61 62 63 64 65 66 67 0a 00 00 00 00 00 00 00 00 |abcdefg.........| ZONE8
00002010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00002400 04 00 2e 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| ZONE9
00002410 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00002420 01 00 2e 2e 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00002430 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00002440 05 00 75 6e 61 6d 65 2e 74 78 74 00 00 00 00 00 |..uname.txt.....|
00002450 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00002800 4c 69 6e 75 78 20 75 62 75 6e 74 75 20 34 2e 31 |Linux ubuntu 4.1| ZONE10
00002810 35 2e 30 2d 33 36 2d 67 65 6e 65 72 69 63 20 23 |5.0-36-generic #|
00002820 33 39 7e 31 36 2e 30 34 2e 31 2d 55 62 75 6e 74 |39~16.04.1-Ubunt|
00002830 75 20 53 4d 50 20 54 75 65 20 53 65 70 20 32 35 |u SMP Tue Sep 25|
00002840 20 30 38 3a 35 39 3a 32 33 20 55 54 43 20 32 30 | 08:59:23 UTC 20|
00002850 31 38 20 78 38 36 5f 36 34 20 78 38 36 5f 36 34 |18 x86_64 x86_64|
00002860 20 78 38 36 5f 36 34 20 47 4e 55 2f 4c 69 6e 75 | x86_64 GNU/Linu|
00002870 78 0a 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |x...............|
00002880 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
000200000. Boot block
The first 1KB is the boot area, which is used to store the boot code of the system startup. It is not used and all are 0;
1. Super block
The minix file system superblock takes up 1KB:
00000400 40 00 80 00 01 00 01 00 06 00 00 00 00 1c 08 10 |@...............| 超级块
00000410 8f 13 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000420 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*struct minix_super_block {
__u16 s_ninodes; //0x0040, 64个索引节点
__u16 s_nzones; //0x0080, 128个zone, 每个1K
__u16 s_imap_blocks; //0x0001, inode 位图点用一个块（1KB）
__u16 s_zmap_blocks; //0x0001, zone位图占用一个块（1KB）
__u16 s_firstdatazone; //0x0006第一个数据ZONE索引号
__u16 s_log_zone_size; //0x0000, log2(zone/block), zone与block 都为1024
__u32 s_max_size; //0x10081c00, 十进制268966912， 文件最大尺寸
__u16 s_magic; //0x138f（MINIX1.0文件系统）
__u16 s_state;
__u32 s_zones;
};2. inode bitmap
3f 00 00 00 00 00 00 00
0011_1111 ......bit0 is reserved but set to 1, and bit1 indicates the root directory of the file system, occupying a total of 5 inodes (root directory, document and 3 files).
3. zone bitmap
3f 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f8
0011_1111 ......Bit0 is reserved but set to 1. Bit1 represents the root directory data area of the file system (storing multiple directory entries), which occupies a total of 5 zones. The firstdatazone of the previous super block is 6, so bit1 here corresponds to DataZone 6 and bit2 corresponds to 7. , bit3 corresponds to 8...
4. inode
00001000 ed 41 e8 03 a0 00 00 00 1b 92 f3 5b e8 03 06 00 |.A.........[....| inode1
00001010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001020 b4 81 e8 03 0a 00 00 00 ec 91 f3 5b e8 01 07 00 |...........[....| inode2
00001030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001040 b4 81 e8 03 08 00 00 00 0f 92 f3 5b e8 01 08 00 |...........[....| inode3
00001050 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001060 fd 41 e8 03 60 00 00 00 35 92 f3 5b e8 02 09 00 |.A..`...5..[....| inode4
00001070 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001080 b4 81 e8 03 72 00 00 00 35 92 f3 5b e8 01 0a 00 |....r...5..[....| inode5
00001090 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*32 bytes is an inode, the first two lines are the inode of the root directory, the inode number is 1; the inode is 0 means free:
struct minix_inode {
__u16 i_mode; //0x41ed, 040755, 目录文件, rwxr-xr-x
__u16 i_uid; //0x03e8, 1000
__u32 i_size; //000000a0, 160
__u32 i_time; //0x5bf3921b
__u8 i_gid; //0xE8, 232
__u8 i_nlinks; //0x03, 自身引用，上级目录引用，document引用
__u16 i_zone[9]; //0x06, 0x00..... 目前只占用了6号ZONE，存储目录项
};stat device root directory (current directory) output verification:
konga@ubuntu:~/work/temp/mnt$ stat .
File: '.'
Size: 160 Blocks: 2 IO Block: 1024 directory
Device: 700h/1792d Inode: 1 Links: 3
Access: (0755/drwxr-xr-x) Uid: ( 1000/ konga) Gid: ( 232/ UNKNOWN)
Access: 2018-11-20 12:48:28.000000000 +0800
Modify: 2018-11-20 12:48:27.000000000 +0800
Change: 2018-11-20 12:48:27.000000000 +0800
Birth: -The next two lines, inode is 2, content analysis:
struct minix_inode {
__u16 i_mode; // 0x81b4, 0100664 常规文件 rw-rw-r--
__u16 i_uid; // 0x03e8, 1000
__u32 i_size; // 0000000a, 10
__u32 i_time; // 0x5bf391ec
__u8 i_gid; // 0xE8, 232
__u8 i_nlinks; // 0x01, 没有其他硬链接
__u16 i_zone[9]; //0x07, 0x00..... 目前只占用了7号ZONE，存储目录项
};konga@ubuntu:~/work/temp/mnt$ stat number.txt
File: 'number.txt'
Size: 10 Blocks: 2 IO Block: 1024 regular file
Device: 700h/1792d Inode: 2 Links: 1
Access: (0664/-rw-rw-r--) Uid: ( 1000/ konga) Gid: ( 1000/ konga)
Access: 2018-11-20 12:47:40.000000000 +0800
Modify: 2018-11-20 12:47:40.000000000 +0800
Change: 2018-11-20 12:47:40.000000000 +0800
Birth: -
5. DATA
The first data ZONE starts from the 6th block. The first 1KB here is the data area of the current file system root directory, corresponding to bit1 of the zone bitmap; ZONE7 is number.txt corresponding to the i_zone[9] record occupied by inode2. One block stores the file contents.
00001800 01 00 2e 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| ZONE 6
00001810 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001820 01 00 2e 2e 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001830 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001840 02 00 6e 75 6d 62 65 72 2e 74 78 74 00 00 00 00 |..number.txt....|
00001850 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001860 03 00 74 65 78 74 2e 74 78 74 00 00 00 00 00 00 |..text.txt......|
00001870 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00001880 04 00 64 6f 63 75 6d 65 6e 74 00 00 00 00 00 00 |..document......|
00001890 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00001c00 31 32 33 34 35 36 37 38 39 0a 00 00 00 00 00 00 |123456789.......| ZONE7
00001c10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*ZONE6 stores directory entries, here is 32 bytes for a project entry.
struct minix_dir_entry {
__u16 inode;
char name[0];
};The first two directory items are the current directory "." and the previous directory ".."