老师推荐的书是《The Design of the UNIX Operating System》，有压力，每天都觉得自己在欠技术债。
引用阮一峰写的一篇日志，他将对inode的理解写的通俗易懂，点个赞。
inode的内容
[root@chances126 product]# stat hn_dcms.sql
File: "hn_dcms.sql"
Size: 6375968 Blocks: 12456 IO Block: 4096 普通文件
Device: 808h/2056d Inode: 9459975 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2016-01-29 14:27:19.618772319 +0800
Modify: 2016-01-29 14:26:34.897772357 +0800
Change: 2016-01-29 14:26:34.897772357 +0800
Blocks 占用数目的单位 是什么？ Block 还是 sector?
block size 512,分配时4个block 一起分配 一个整数
12456/4=3114
[root@chances126 product]# fdisk -lu /dev/sda8
Disk /dev/sda8: 221.0 GB, 220971663360 bytes
255 heads, 63 sectors/track, 26864 cylinders, total 431585280 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x00000000
每个sector为512，IO block 为4096
[root@chances126 product]# stat hn_dcms.sql
File: "hn_dcms.sql"
Size: 6375968 Blocks: 12456 IO Block: 4096 普通文件
Device: 808h/2056d Inode: 9459975 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2016-01-29 14:27:19.618772319 +0800
Modify: 2016-01-29 14:26:34.897772357 +0800
Change: 2016-01-29 14:26:34.897772357 +0800
获取文件对应的inode信息
File sizes/ Sector = 共需多少个Sector
6375968 / 512 = 12453.0625 = 12454
8个sector 为一个block ，因此所需Block为=12454/8=1556.75
虽有偏差，但能大致能对应上，但有个问题：
计算出的 Sector是 12454，查询出的Blocks: 12456 ，还有2个Sector 也就是1024字节 是什么呢？
[root@chances126 product]# debugfs /dev/sda8
debugfs: stat hn_dcms.sql
Inode: 9459975 Type: regular Mode: 0644 Flags: 0x80000
Generation: 2744091751 Version: 0x00000000:00000001
User: 0 Group: 0 Size: 6375968
File ACL: 0 Directory ACL: 0
Links: 1 Blockcount: 12456
Fragment: Address: 0 Number: 0 Size: 0
ctime: 0x56ab061a:d60bad14 -- Fri Jan 29 14:26:34 2016
atime: 0x56ab0647:9386dd7c -- Fri Jan 29 14:27:19 2016
mtime: 0x56ab061a:d60bad14 -- Fri Jan 29 14:26:34 2016
crtime: 0x56ab061a:05e7fc20 -- Fri Jan 29 14:26:34 2016
Size of extra inode fields: 28
EXTENTS:
(0-1556): 38119424-38120980
(0-1556): 38119424-38120980 为文件数据具体在磁盘上的位置
inode 大小
[root@chances126 product]# sudo dumpe2fs -h /dev/sda8 | grep "Inode size"
dumpe2fs 1.41.12 (17-May-2010)
Inode size: 256
