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I just partitioned my hard disk, and made the sdb6, sdb7.

next, I installed file systems, reiserfs, on sdb6 and ,xfs, on sdb7.

after that, I viewed my hard disk information using fdisk -l, but found that sdb6, sdb7 have FAT12 systems. is that something wrong? or IS FAT12 somewhat same with reiserfs, xfs ?

Disk /dev/sda: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0xe9ffe9ff

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1       10199    81923436    7  HPFS/NTFS
/dev/sda2           10200       19457    74364885    f  W95 Ext'd (LBA)
/dev/sda5           10200       19457    74364853+   7  HPFS/NTFS

Disk /dev/sdb: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0xf16cf16c

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *           1       10199    81923436    7  HPFS/NTFS
/dev/sdb2           10200       19457    74364885    f  W95 Ext'd (LBA)
/dev/sdb5           10200       19075    71296438+   7  HPFS/NTFS
/dev/sdb6           19076       19267     1542208+   1  FAT12
/dev/sdb7           19268       19457     1526143+   1  FAT12
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migrated from stackoverflow.com Apr 9 '11 at 14:08

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3 Answers 3

up vote 2 down vote accepted

The MBR partition type flag may be set to FAT12, but that is erroneous. That doesn't mean that ReiserFS and XFS even remotely resemble FAT12 (they don't). Most modern software don't even look at the partition type flag anymore, as it doesn't even cover the range of filesystems available today; they look at the superblock of the file system directly and identify it accurately.

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you mean when using fdisk -l, showed term "System" doesn't mean filesystem? –  KayKay Apr 9 '11 at 14:02
1  
@KayKay It means file system, yes, but the information's wrong. It's not stored as a name on the disk, but as a numeric identifier code; and AFAIK we ran out of available codes some time ago. –  Daniel Beck Apr 9 '11 at 14:15
    
thanks. and i knew i can change FAT12 to linux with t command^^ –  KayKay Apr 11 '11 at 14:43

FAT12 was used in older floppy disk drives and was limited to 32mb. So, chances are you simply have mislabeled partitions. There's no reason it should be on a HDD partition.

It predates reiser and XFS (and ext2/3/4) by a fair bit as well.

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As others have pointed out, what fdisk is telling you is the partition type, not the filesystem format used on the volume. Partition types do not denote, and really have never denoted, filesystem formats; and to determine the filesystem format you must usually probe the actual contents of the volume. Such probing is done by mount when it is autodetecting the filesystem format, for example.

The partition type is simply a field in the partition table, and all that it really controls is which operating systems will try to mount the volume. Operating systems know what partition types they understand, and thus will attempt to automatically mount by default.

It's confusing that some people mistakenly call partition types things like FAT12 or HPFS, and that these misnomers have made their ways into things like fdisk. Try to ignore this confusion. The filesystem format is actually governed in such cases by the actual volume contents and labels such as FAT12 and NTFS for the partition types are simply misnomers. Better labels would be something like Microsoft Data partition <1KiCyl <16GiB and Microsoft Data partition (OS/2 and Windows NT only), respectively, because that is what type codes 01 and 07 actually denote to operating systems.

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