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Créer une clé USB en FAT32

Afin qu’il soit lisible par d’autres systèmes (par exemple un disque USB pour des sauvegardes), voici les différentes étapes pour initialiser un disques en FAT32. Prenons l’exemple avec disque sd1 ajouté. Il faut d’abord initialiser sa table des partitions :

# fdisk -i sd1

        -----------------------------------------------------
        ------ ATTENTION - UPDATING MASTER BOOT RECORD ------
        -----------------------------------------------------

Do you wish to write new MBR and partition table? [n] y

On indique ensuite que la partition est de type FAT32 :

# fdisk -e sd1
Enter 'help' for information
fdisk: 1> p
Disk: sd1       geometry: 60801/255/63 [976773168 Sectors]
Offset: 0       Signature: 0xAA55
            Starting         Ending         LBA Info:
 #: id      C   H   S -      C   H   S [       start:        size ]
-------------------------------------------------------------------------------
 0: 00      0   0   0 -      0   0   0 [           0:           0 ] unused      
 1: 00      0   0   0 -      0   0   0 [           0:           0 ] unused      
 2: 00      0   0   0 -      0   0   0 [           0:           0 ] unused      
*3: A6      0   1   1 -  60800 254  63 [          63:   976768002 ] OpenBSD     
fdisk: 1> e 3
            Starting         Ending         LBA Info:
 #: id      C   H   S -      C   H   S [       start:        size ]
-------------------------------------------------------------------------------
*3: A6      0   1   1 -  60800 254  63 [          63:   976768002 ] OpenBSD
Partition id ('0' to disable)  [0 - FF]: [A6] (? for help) ?
Choose from the following Partition id values:
00 unused         20 Willowsoft     67 Novell         AB MacOS X boot
01 DOS FAT-12     24 NEC DOS        68 Novell         AF MacOS X HFS+
02 XENIX /        38 Theos          69 Novell         B7 BSDI filesy*
03 XENIX /usr     39 Plan 9         70 DiskSecure     B8 BSDI swap   
04 DOS FAT-16     40 VENIX 286      75 PCIX           BF Solaris     
05 Extended DOS   41 Lin/Minux DR   80 Minix (old)    C0 CTOS        
06 DOS > 32MB     42 LinuxSwap DR   81 Minix (new)    C1 DRDOSs FAT12
07 HPFS/QNX/AUX   43 Linux DR       82 Linux swap     C4 DRDOSs < 32M
08 AIX fs         4D QNX 4.2 Pri    83 Linux files*   C6 DRDOSs >=32M
09 AIX/Coherent   4E QNX 4.2 Sec    84 OS/2 hidden    C7 HPFS Disbled
0A OS/2 Bootmgr   4F QNX 4.2 Ter    85 Linux ext.     DB CPM/C.DOS/C*
0B Win95 FAT-32   50 DM             86 NT FAT VS      DE Dell Maint  
0C Win95 FAT32L   51 DM             87 NTFS VS        E1 SpeedStor   
0E DOS FAT-16     52 CP/M or SysV   8E Linux LVM      E3 SpeedStor   
0F Extended LBA   53 DM             93 Amoeba FS      E4 SpeedStor   
10 OPUS           54 Ontrack        94 Amoeba BBT     EB BeOS/i386   
11 OS/2 hidden    55 EZ-Drive       99 Mylex          EE EFI GPT     
12 Compaq Diag.   56 Golden Bow     9F BSDI           EF EFI Sys     
14 OS/2 hidden    5C Priam          A0 NotebookSave   F1 SpeedStor   
16 OS/2 hidden    61 SpeedStor      A5 FreeBSD        F2 DOS 3.3+ Sec
17 OS/2 hidden    63 ISC, HURD, *   A6 OpenBSD        F4 SpeedStor   
18 AST swap       64 NetWare 2.xx   A7 NEXTSTEP       FF Xenix BBT   
19 Willowtech     65 NetWare 3.xx   A8 MacOS X     
1C ThinkPad Rec   66 NetWare 386    A9 NetBSD      
Partition id ('0' to disable)  [0 - FF]: [A6] (? for help) 0B
Do you wish to edit in CHS mode? [n]
offset: [63]
size: [976768002]
fdisk:*1> w
Writing MBR at offset 0.
fdisk: 1> q

La partition est ainsi accessible en sd1i comme l’indique disklabel :

# disklabel sd1
disklabel: warning, DOS partition table with no valid OpenBSD partition
# /dev/rsd1c:
type: SCSI
disk: SCSI disk
label: HM500JI
flags:
bytes/sector: 512
sectors/track: 63
tracks/cylinder: 255
sectors/cylinder: 16065
cylinders: 60801
total sectors: 976773168
rpm: 3600
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0           # microseconds
track-to-track seek: 0  # microseconds
drivedata: 0

16 partitions:
#                size           offset  fstype [fsize bsize  cpg]
  c:        976773168                0  unused      0     0
  i:        976768002               63   MSDOS

Enfin, on la formate ensuite en FAT32 :

# newfs_msdos sd1i
/dev/rsd1i: 974863936 sectors in 121857992 FAT32 clusters (4096 bytes/cluster)
bps=512 spc=8 res=32 nft=2 mid=0xf8 spt=63 hds=255 hid=63 bsec=976768002 bspf=952016 rdcl=2 infs=1 bkbs=2

Tutoriel volé sur le wiki d'evolix.