°Ô½Ã¹° 20°Ç
   
[SUSE] ¼öÆÛºí·Ï º¹±¸ ¹æ¹ý
±Û¾´ÀÌ : theko ³¯Â¥ : 2012-09-23 (ÀÏ) 11:12 Á¶È¸ : 4640

EXT2 filesystem

In my machine, there is an ext2 filesystem /dev/sda6 which its mount point is /fs2.

Firstly, I should know the location of superblocks and the size of block.
[root@localhost ~]# dumpe2fs /dev/sda6 | grep –i superblock
dumpe2fs 1.40.8 (13-Mar-2008)
  Primary superblock at 1, Group descriptors at 2-2
  Backup superblock at 8193, Group descriptors at 8194-8194
  Backup superblock at 24577, Group descriptors at 24578-24578
  Backup superblock at 40961, Group descriptors at 40962-40962
  Backup superblock at 57345, Group descriptors at 57346-57346
  Backup superblock at 73729, Group descriptors at 73730-73730
[root@localhost ~]# dumpe2fs /dev/sda6 | grep –i ¡®block size¡¯
dumpe2fs 1.40.8 (13-Mar-2008)
Block size:                               1024 

From the above, I knew there are 5 backup superblocks and the block size is 1024 bytes. The location of primary superblock is at 1. The locations of these 5 backup superblocks are at 8193,24577,40961,57345 and 73729 respectively. If you want to know the filesystem¡¯s block size, there are another two ways that you can use tune2fs and ext3grep commands. For example,
[root@localhost ~]# tune2fs –l dev/sda6 | grep –i ¡®block size¡¯
[root@localhost ~]# ext3grep /dev/sda6 | grep –i ¡®block size¡¯ 

Then, I destroyed the superblock as below.
[root@localhost ~]# dd if=/dev/zero count=1 bs=1024 seek=1 of=/dev/sda6 

I checked the effect, and found I still could change to /fs2 directory. I could still list its contents. But the system gave me error messages when I tried to create a file or copy files.
[root@localhost ~]# cd /fs2
[root@localhost ~]# ll
total 19
drwx—— 2 root root 12288 2009-06-25 08:57 lost+found
-rw-r—r—1 root root   135 2009-06-25 18:15 qaz
 ¡¦ ¡¦ 

[root@localhost fs2]#cp qaz wsx
cp: overwrite  `wsx¡¯? y
cp: writing `wsx¡¯: No space left on device
 [root@localhost fs2]#cp qaz edc
cp: cannot create regular file `edc¡¯: Input/output error 

When I run the dumpe2fs command, it told me the superblock had been destroyed.
[root@localhost fs2]#dumpe2fs /dev/sda6
dumpe2fs 1.40.8 (13-Mar-2008)
dumpe2fs: Bad magic number in super-block while trying to open /dev/sda6
Couldn¡¯t find valid filesystem superblock. 

I recovered the superblock.
[root@localhost ~]# dd if=/dev/sda6 count=1 bs=1024 skip=8193 seek=1 of=/dev/sda5

After that, I checked if I can create and copy files. I found they worked. And the command dumpe2fs could display normally. 

EXT3 filesystem

In my machine, there is another ext3 filesystem /dev/sda5 which its mount point is /fs3.

Check the location of superblocks and the size of block.
[root@localhost ~]# dumpe2fs /dev/sda5 | grep –i superblock
dumpe2fs 1.40.8 (13-Mar-2008)
  Primary superblock at 0, Group descriptors at 1-1
  Backup superblock at 32768, Group descriptors at 32769-32769
  Backup superblock at 98304, Group descriptors at 98305-98305
  Backup superblock at 163840, Group descriptors at 163841-163841
  Backup superblock at 229376, Group descriptors at 229377-22937
[root@localhost ~]# dumpe2fs /dev/sda5 | grep –i ¡®block size¡¯
dumpe2fs 1.40.8 (13-Mar-2008)
Block size:                               4096 

From the above, I knew there are 4 backup superblocks and the block size is 4096 bytes. The location of primary superblock is at 0. The locations of these 4 backup superblocks are at 32768, 98304, 163840, and 229376.

Destroy the superblock.
[root@localhost ~]# dd if=/dev/zero count=1 bs=4096 seek=0 of=/dev/sda5 

I found I still can change to /fs3 directory. But when I listed its contents, there is nothing. I used dumpe2fs command to check, it told me the superblock has problem. Then I tried to recover the superblock like the above approach, however, it did not work. I restarted the system. The system displayed it unable to resolve the filesystem and could not boot up. I entered the maintenance mode and tried to recover using the method as below. It did not work.
(Repair filesystem) 1 # e2fsck –f –b 32768 /dev/sda5
e2fsck 1.40.8 (13-Mar-2008)
e2fsck: Device or resource busy while trying to open /dev/sda5
Filesystem mounted or opened exclusively by another program? 

Then I used another method, after I reboot the system it worded.
(Repair filesystem) 2 # e2fsck –f  /dev/sda5
(Repair filesystem) 3 # reboot 

From the test, I realized that the information of the filesystem¡¯s superblock is very important. We¡¯d better backup it to the root because we can still read it through maintenance mode even if the system can not boot up normally. Don¡¯t forget run the following command.
#dumpe2fs /dev/sda5 > /dumpe2fs-sda5


À̸§ Æнº¿öµå
ºñ¹Ð±Û (üũÇÏ¸é ±Û¾´À̸¸ ³»¿ëÀ» È®ÀÎÇÒ ¼ö ÀÖ½À´Ï´Ù.)
¿ÞÂÊÀÇ ±ÛÀÚ¸¦ ÀÔ·ÂÇϼ¼¿ä.
   

miwit.com sir.co.kr DNS Powered by DNSEver.com DNS Powered by DNSEver.com