关于os的一些整理：第六篇：文件系统

文件系统

系统安装的时候就应该根据磁盘分区表在各个分区上建立文件系统。

 

建立文件系统的过程其实就是对磁盘进行一次格式化。也就是上面提到的软格式化。

从哪里开始文件系统的工作？

在开发的时候，可以在开始的时候，初始化时根据磁盘分区信息在各个分区上建立文件系统，以便开始文件系统的工作，同时便于后面开始做些文件系统以及文件相关的操作。

 

磁盘分区

 

磁盘分区表

 

写道

| |
| ... |
------+-----+--- ~
^ ^ | | ^
| 64k+-----+ | 1048575:0xfffff
| v | ... | |
| ---+-----+ | 983040:0xf0000
| ^ | | |
| 64k+-----+ | 983039:0xeffff
| v | ... | |
| ---+-----+ | 917504:0xe0000
| | | |
| +-----+ | 917503:0xdffff
| | ... | |
| +-----+ | 851968:0xd0000
| | | |
| +-----+ | 851967:0xcffff
| | ... | |
| +-----+ | 786432:0xc0000
| | | |
| +-----+ | 786431:0xbffff
| | ... | |
| +-----+ | 753664:0xb8000
| | | |
| +-----+ | 753663:0xb7fff
| | ... | |
| +-----+ | 720896:0xb0000
| | | |
| +-----+ | 720895:0xaffff
| | ... | |
| +-----+ | 655360:0xa0000
| | | |
| +-----+ | 655359:0x9ffff
| | ... | |
| +-----+ | 589824:0x90000
| | | |
| +-----+ | 589823:0x8ffff
| | ... | |
| +-----+ 1M 524288:0x80000
| | | |
| +-----+ | 524287:0x7ffff
| | ... | |
| +-----+ | 458752:0x70000
| | | |
| +-----+ | 458751:0x6ffff
Low | ... | |
Memory +-----+ | 393216:0x60000
(1M) | | |
| +-----+ | 393215:0x5ffff
| | ... | |
| +-----+ | 327680:0x50000
| | | |
| +-----+ | 327679:0x4ffff
| | ... | |
| +-----+ | 262144:0x40000
| | | |
| +-----+ | 262143:0x3ffff
| | ... | |
| ---+-----+ | 196608:0x30000
| ^ | | |
| 64k+-----+ | 196607:0x2ffff
| v | ... | |
| ---+-----+ | 131072:0x20000
| ^ | | |
| 64k+-----+ | 131071:0x1ffff
| v | ... | |
| ---+-----+ | 65536:0x10000
| ^ | | |
| 64k+-----+ | 65535:0x0ffff
| | | ... | |
| | +-----+ | 32256:0x07e00 - -
| | |0xaa | | ^ ^
| | +-----+ | 32255:0x07dff, mbr to here. boot sector:512 bytes 0xaa55
| | |0x55 | | | v
| | +-----+ | 32254:0x07dfe | - -
| | | ... | | | ^ ^
| | +-----+ | 32239:0x07def | | the 4th partition:16 bytes -
| | | | | | | v Boot indicator
| | +-----+ | 32238:0x07dee | | - -
| | | ... | | | | ^
| | +-----+ | 32223:0x07ddf | | the 3rd partition:16 bytes -
| | | | | | | v Boot indicator
| | +-----+ | 32222:0x07dde | dpt - -
| | | ... | | | | ^
| | +-----+ | 32207:0x07dcf | | the 2nd partition:16 bytes -
| | | | | | | v Boot indicator
| | +-----+ | 32206:0x07dce | | - -
| | | ... | | | | ^ ^
| | +-----+ | 32203:0x07dcb | | | Number of sectors in the partition:4 bytes
| | | | | | | | v
| | +-----+ | 32202:0x07dca | | | -
| | | ... | | | | | ^
| | +-----+ | 32199:0x07dc7 | | | Number of sectors preceding the partition:4 bytes
| | | | | | | | v
| | +-----+ | 32198:0x07dc6 | | | -
| | | | | | | | Ending low cylinder number
| | +-----+ | 32197:0x07dc5 | | | -
| | | | | | | | Ending sector and high cylinder number
| | +-----+ | 32196:0x07dc4 | | | -
| | | | | | | | Ending head number
| | +-----+ | 32195:0x07dc3 | | | -
| | | | | | | | System indicator
| | +-----+ | 32194:0x07dc2 | | | -
| | | | | | | | Beginning low cylinder number
| | +-----+ | 32193:0x07dc1 | | | -
| | | | | | | | Beginning sector and high cylinder number
| | +-----+ | 32192:0x07dc0 | | | -
| | | | | | | | Beginning head number
| | +-----+ | 32191:0x07dbf | | the 1st partition:16 bytes -
| | | | | | v v Boot indicator
| | +-----+ | 32190:0x07dbe | - - -
| | | ... | | (512 bytes places mbr) v
| | +-----+ | 31744:0x07c00, 0x007c0:0x0000, 0x00000:0x7c00. mbr from here.-
| | | | |
| | +-----+ | 31743:0x07bff
| | | ... | |
| | +-----+ | 01280:0x00500
| | | | |
| | +-----+ |
| | | ... | |
| | +-----+ |
| | | | |
| | +-----+ |
| | | ... | |
| | +-----+ | 01024:0x00400
| | | | |
| | +-----+ | 01023:0x003ff
v v | ... | v
------+-----+--- 00000:0x00000

 

初始化分区

在引导扇区中有一块区域存放分区信息。在编写主引导程序的时候可以对分区进行初始化。当然也可以在主引导程序中不对磁盘分区进行初始化，而在后面，如进入内核程序执行时对它进行初始化。

 

读取分区信息

根据分区信息在分区上建立文件系统。

 

分区盘符

盘符是windows系统中常见的概念。它其实就是一个分区。

 

内核加载并执行后，最好将磁盘分区表将主引导扇区移动到内核位置，以便内核加载读取磁盘分区表，并根据磁盘分区表加载文件系统。移动到内核位置也比较安全。

 

 

文件系统

 

 

文件系统格式

 

FAT

https://www.iteye.com/blog/lobin-2433943

 

EXT

https://www.iteye.com/blog/lobin-2311779

 

什么时候建立文件系统？

系统安装的时候就应该根据磁盘分区表在各个分区上建立文件系统。

 

建立文件系统的过程其实就是对磁盘进行一次格式化。也就是上面提到的软格式化。

 

文件系统操作

 

 

 

FAT

 

EXT

 

文件系统接口