在sdb上挂载USB 设备

 

在主机上挂载 USB 设备后我们查看系统当前磁盘设备：
1. [root@FCoE ~]# fdisk -l  
2. 
3. Disk /dev/sda: 43.0 GB, 42991616000 bytes  
4. 255 heads, 63 sectors/track, 5226 cylinders  
5. Units = cylinders of 16065 * 512 = 8225280 bytes  
6. Sector size (logical/physical): 512 bytes / 512 bytes  
7. I/O size (minimum/optimal): 512 bytes / 512 bytes  
8. Disk identifier: 0x00032735  
9. 
10.   Device Boot      Start         End      Blocks   Id  System  
11. /dev/sda1   *           1          17      131072   83  Linux  
12. Partition 1 does not end on cylinder boundary.  
13. /dev/sda2              17         147     1048576   82  Linux swap / Solaris  
14. Partition 2 does not end on cylinder boundary.  
15. /dev/sda3             147        5227    40803328   83  Linux  
16. 
17. Disk /dev/sdb: 2147 MB, 2147483648 bytes  
18. 255 heads, 63 sectors/track, 261 cylinders  
19. Units = cylinders of 16065 * 512 = 8225280 bytes  
20. Sector size (logical/physical): 512 bytes / 512 bytes  
21. I/O size (minimum/optimal): 512 bytes / 512 bytes  
22. Disk identifier: 0x00000000  
23. 
24. Disk /dev/sdb doesn't contain a valid partition table 
ocp认证现在我们在 sdb 这个设备上创建一个新的分区：
1. [root@FCoE ~]# fdisk /dev/sdb  
2. Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel  
3. Building a new DOS disklabel with disk identifier 0xcdd48395.  
4. Changes will remain in memory only, until you decide to write them.  
5. After that, of course, the previous content won't be recoverable.  
6. 
7. Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)  
8. 
9. WARNING: DOS-compatible mode is deprecated. It's strongly recommended to  
10.         switch off the mode (command 'c') and change display units to  
11.         sectors (command 'u').  
12. 
13. Command (m for help): n  
14. Command action  
15.   e   extended  
16.   p   primary partition (1-4)  
17. p  
18. Partition number (1-4): 1  
19. First cylinder (1-261, default 1):  
20. Using default value 1  
21. Last cylinder, +cylinders or +size{K,M,G} (1-261, default 261):  
22. Using default value 261  
23. 
24. Command (m for help): p  
25. 
26. Disk /dev/sdb: 2147 MB, 2147483648 bytes  
27. 255 heads, 63 sectors/track, 261 cylinders  
28. Units = cylinders of 16065 * 512 = 8225280 bytes  
29. Sector size (logical/physical): 512 bytes / 512 bytes  
30. I/O size (minimum/optimal): 512 bytes / 512 bytes  
31. Disk identifier: 0xcdd48395  
32. 
33.   Device Boot      Start         End      Blocks   Id  System  
34. /dev/sdb1               1         261     2096451   83  Linux  
35. 
36. Command (m for help): w  
37. The partition table has been altered!  
38. 
39. Calling ioctl() to re-read partition table.  
40. Syncing disks. 
ocp认证在新分区 sdb1 上创建文件系统：
1. [root@FCoE ~]# mkfs.ext3 /dev/sdb1  
2. mke2fs 1.41.12 (17-May-2010)  
3. Filesystem label=  
4. OS type: Linux  
5. Block size=4096 (log=2)  
6. Fragment size=4096 (log=2)  
7. Stride=0 blocks, Stripe width=0 blocks  
8. 131072 inodes, 524112 blocks  
9. 26205 blocks (5.00%) reserved for the super user  
10. First data block=0  
11. Maximum filesystem blocks=536870912  
12. 16 block groups  
13. 32768 blocks per group, 32768 fragments per group  
14. 8192 inodes per group  
15. Superblock backups stored on blocks:  
16.        32768, 98304, 163840, 229376, 294912  
17. 
18. Writing inode tables: done  
19. Creating journal (8192 blocks): done  
20. Writing superblocks and filesystem accounting information: done  
21. 
22. This filesystem will be automatically checked every 24 mounts or  
23. 180 days, whichever comes first.  Use tune2fs -c or -i to override. 
ocp认证挂载新的文件系统：
1. [root@FCoE ~]# mount /dev/sdb1 /mnt/ 
ocp认证通常我们通过备份硬盘的 MBR 来备份硬盘分区表：
1. [root@FCoE ~]# dd if=/dev/sda of=/mnt/sda.mbr bs=512 count=1  
2. 1+0 records in  
3. 1+0 records out  
4. 512 bytes (512 B) copied, 0.000777948 s, 658 kB/s 
ocp认证现在我们来写零硬盘分区表来实现类似分区表被破坏的结果：
1. [root@FCoE ~]# dd if=/dev/zero of=/dev/sda bs=1 count=64 skip=446 seek=446  
2. 64+0 records in  
3. 64+0 records out  
4. 64 bytes (64 B) copied, 0.00160668 s, 39.8 kB/s 
ocp认证查询硬盘 sda 上的分区信息，发现其已不包含任何分区：
1. [root@FCoE ~]# fdisk -l  
2. 
3. Disk /dev/sda: 43.0 GB, 42991616000 bytes  
4. 255 heads, 63 sectors/track, 5226 cylinders  
5. Units = cylinders of 16065 * 512 = 8225280 bytes  
6. Sector size (logical/physical): 512 bytes / 512 bytes  
7. I/O size (minimum/optimal): 512 bytes / 512 bytes  
8. Disk identifier: 0x00032735  
9. 
10.   Device Boot      Start         End      Blocks   Id  System  
11. 
12. Disk /dev/sdb: 2147 MB, 2147483648 bytes  
13. 255 heads, 63 sectors/track, 261 cylinders  
14. Units = cylinders of 16065 * 512 = 8225280 bytes  
15. Sector size (logical/physical): 512 bytes / 512 bytes  
16. I/O size (minimum/optimal): 512 bytes / 512 bytes  
17. Disk identifier: 0xcdd48395  
18. 
19.   Device Boot      Start         End      Blocks   Id  System  
20. /dev/sdb1               1         261     2096451   83  Linux 
当主机硬盘分区表丢失了之后，再次启动后 GRUB 会因找不到配置文件而进入命令行模式。