리눅스 (하드링크&소프트링크)

장치파일


[root@hostname /root]# df -h
Filesystem Size  Used  Avail  Use% Mounted on
/dev/hda1  39G   2.5G  35G    7%   /
/dev/hda5  132G  24G   102G   19%  /home
tmpfs      2.0G  0     2.0G   0%   /dev/shm
/dev/hda2  49G   309M  46G    1%   /backup

[root@systech-dev /root]# ls -l /dev/hda1
brw-r----- 1 root disk 3, 1 2011-12-03 10:58 /dev/hda1

3, 1 은 커널이 장치를 식별하는 식별자이며, Major Number 식별자는 3, Minor Number 식별자는 1 임을 의미한다.

Block 장치파일 I/O단위(Block)
Character 장치파일 I/O단위(Byte)


하드링크 - inode 데이터블럭 낭비가 없다.

[root@systech-dev /root/test]# touch a.txt

[root@systech-dev /root/test]# ln a.txt b.txt
[root@systech-dev /root/test]# cp -p a.txt c.txt
[root@systech-dev /root/test]# ls -l
total 0
-rw-r--r-- 2 root root 0 2012-11-29 00:40 a.txt
-rw-r--r-- 2 root root 0 2012-11-29 00:40 b.txt
-rw-r--r-- 1 root root 0 2012-11-29 00:40 c.txt

a.txt 는 원본이고 b.txt 는 링크이다. (원본과 링크의 구별이 어려움)

-rw-r--r-- 다음으로 오는 숫자는 하드링크가 걸린 갯수를 나타낸다.
c.txt 는 하드링크가 자기 자신밖에 없으므로 1이 된다.

b.txt 는 a.txt 가 사용하는 데이터 블록을 같이 사용하며, inode table도 같이 사용한다.
원본 = 하드링크라고도 말할 수 있음(원본이 지워져도 링크파일에는 지장 없다.)



inode table 파일 속성 정보

[root@systech-dev /etc]# dumpe2fs /dev/hda1 | more
dumpe2fs 1.39 (29-May-2006)
Filesystem volume name:   /
Last mounted on:          <not available>
Filesystem UUID:          3e6cd2fe-ff77-471c-a7f8-57905b81c67f
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      has_journal ext_attr resize_inode dir_index filetype n
eeds_recovery sparse_super large_file
Default mount options:    user_xattr acl
Filesystem state:         clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              10487712
Block count:              10486420
Reserved block count:     524321
Free blocks:              9626144
Free inodes:              10407784
First block:              0
Block size:               4096
Fragment size:            4096
Reserved GDT blocks:      1022
Blocks per group:         32760
Fragments per group:      32760
Inodes per group:         32672
Inode blocks per group:   1021
Filesystem created:       Sat Apr 30 16:06:25 2011
Last mount time:          Sat Dec  3 10:58:46 2011
Last write time:          Sat Dec  3 10:58:46 2011
Mount count:              14
Maximum mount count:      -1
Last checked:             Sat Apr 30 16:06:25 2011
Check interval:           0 (<none>)
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:               128
Journal inode:            8
First orphan inode:       5554829
Default directory hash:   tea
Directory Hash Seed:      f67d43ec-3545-45d8-9196-986238fe1726
Journal backup:           inode blocks
Journal size:             128M


Group 0: (Blocks 0-32759)
  Primary superblock at 0, Group descriptors at 1-3
  Reserved GDT blocks at 4-1025
  Block bitmap at 1026 (+1026), Inode bitmap at 1027 (+1027)
  Inode table at 1028-2048 (+1028)
  0 free blocks, 32661 free inodes, 2 directories
  Free blocks:
  Free inodes: 12-32672
Group 1: (Blocks 32760-65519)
  Backup superblock at 32760, Group descriptors at 32761-32763
  Reserved GDT blocks at 32764-33785
  Block bitmap at 33786 (+1026), Inode bitmap at 33787 (+1027)
  Inode table at 33788-34808 (+1028)
  28613 free blocks, 32672 free inodes, 0 directories
  Free blocks: 36907-65519
  Free inodes: 32673-65344
Group 2: (Blocks 65520-98279)
  Block bitmap at 65520 (+0), Inode bitmap at 65521 (+1)
  Inode table at 65522-66542 (+2)
  31729 free blocks, 32664 free inodes, 0 directories
  Free blocks: 66543-75754, 75762, 75764-98279
  Free inodes: 65353-98016
Group 3: (Blocks 98280-131039)
  Backup superblock at 98280, Group descriptors at 98281-98283
  Reserved GDT blocks at 98284-99305
  Block bitmap at 99306 (+1026), Inode bitmap at 99307 (+1027)
  Inode table at 99308-100328 (+1028)
  30711 free blocks, 32670 free inodes, 0 directories
  Free blocks: 100329-131039
  Free inodes: 98019-130688
Group 4: (Blocks 131040-163799)
  Block bitmap at 131040 (+0), Inode bitmap at 131041 (+1)
  Inode table at 131042-132062 (+2)
  31737 free blocks, 32672 free inodes, 0 directories
  Free blocks: 132063-163799
  Free inodes: 130689-163360
Group 5: (Blocks 163800-196559)
  Backup superblock at 163800, Group descriptors at 163801-163803
  Reserved GDT blocks at 163804-164825
  Block bitmap at 164826 (+1026), Inode bitmap at 164827 (+1027)
  Inode table at 164828-165848 (+1028)
  30711 free blocks, 32672 free inodes, 0 directories
  Free blocks: 165849-196559
  Free inodes: 163361-196032
Group 6: (Blocks 196560-229319)
  Block bitmap at 196560 (+0), Inode bitmap at 196561 (+1)
  Inode table at 196562-197582 (+2)
  31737 free blocks, 32672 free inodes, 0 directories
  Free blocks: 197583-229319
  Free inodes: 196033-228704
.
.
.


?
파일의 실제 위치
431715   issue
/etc/issue  -----> 2728546(실제 파일의 위치)
링크파일의 속성변경 -> 원본 파일의 속성이 변경됨



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