D'accord, merci pour l'explication, je crois que je comprends un peu mieux le principe et la possibilité du conflit !
J'ai réalisé les commandes que vous m'avez demandées, les voici :
mornagest@affreux:~$ sudo mkfs.fat -v /dev/sdc2
mkfs.fat 4.1 (2017-01-24)
Auto-selecting FAT32 for large filesystem
/dev/sdc2 has 255 heads and 63 sectors per track,
hidden sectors 0x1385000;
logical sector size is 512,
using 0xf8 media descriptor, with 146325504 sectors;
drive number 0x80;
filesystem has 2 32-bit FATs and 64 sectors per cluster.
FAT size is 17920 sectors, and provides 2285775 clusters.
There are 64 reserved sectors.
Volume ID is 0cf3e21a, no volume label.
mornagest@affreux:~$ sudo fdisk -l | grep sdb
Disque /dev/sdb : 931,5 GiB, 1000204886016 octets, 1953525168 secteurs
mornagest@affreux:~$ sudo blkid | grep sdb
/dev/sdb: LABEL="Sauvegarde2" UUID="d79ea873-1bb0-447f-a480-7578df5e6589" TYPE="ext4"
mornagest@affreux:~$ sudo dd if=/dev/sdc bs=512 count=4 skip=20467712 | hexdump -C
4+0 enregistrements lus
4+0 enregistrements écrits
00000000 eb 58 90 6d 6b 66 73 2e 66 61 74 00 02 40 40 00 |.X.mkfs.fat..@@.|
00000010 02 00 00 00 00 f8 00 00 3f 00 ff 00 00 50 38 01 |........?....P8.|
2048 bytes (2,0 kB, 2,0 KiB) copied, 0,370307 s, 5,5 kB/s
00000020 00 c0 b8 08 00 46 00 00 00 00 00 00 02 00 00 00 |.....F..........|
00000030 01 00 06 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000040 80 00 29 1a e2 f3 0c 4e 4f 20 4e 41 4d 45 20 20 |..)....NO NAME |
00000050 20 20 46 41 54 33 32 20 20 20 0e 1f be 77 7c ac | FAT32 ...w|.|
00000060 22 c0 74 0b 56 b4 0e bb 07 00 cd 10 5e eb f0 32 |".t.V.......^..2|
00000070 e4 cd 16 cd 19 eb fe 54 68 69 73 20 69 73 20 6e |.......This is n|
00000080 6f 74 20 61 20 62 6f 6f 74 61 62 6c 65 20 64 69 |ot a bootable di|
00000090 73 6b 2e 20 20 50 6c 65 61 73 65 20 69 6e 73 65 |sk. Please inse|
000000a0 72 74 20 61 20 62 6f 6f 74 61 62 6c 65 20 66 6c |rt a bootable fl|
000000b0 6f 70 70 79 20 61 6e 64 0d 0a 70 72 65 73 73 20 |oppy and..press |
000000c0 61 6e 79 20 6b 65 79 20 74 6f 20 74 72 79 20 61 |any key to try a|
000000d0 67 61 69 6e 20 2e 2e 2e 20 0d 0a 00 00 00 00 00 |gain ... .......|
000000e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
000001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U.|
00000200 52 52 61 41 00 00 00 00 00 00 00 00 00 00 00 00 |RRaA............|
00000210 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
000003e0 00 00 00 00 72 72 41 61 ce e0 22 00 02 00 00 00 |....rrAa..".....|
000003f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U.|
00000400 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000800
mornagest@affreux:~$ sudo dd if=/dev/disk/by-id/ata-Hitachi_HTS542516K9SA00_071124BB0C00WGHA3N0C-part2 bs=512 count=4 | hexdump -C
4+0 enregistrements lus
4+0 enregistrements écrits
00000000 eb 58 90 6d 6b 66 73 2e 66 61 74 00 02 40 40 00 |.X.mkfs.fat..@@.|
00000010 02 00 00 00 00 f8 00 00 3f 00 ff 00 00 50 38 01 |........?....P8.|
2048 bytes (2,0 kB, 2,0 KiB) copied, 0,364676 s, 5,6 kB/s00000020 00 c0 b8 08 00 46 00 00 00 00 00 00 02 00 00 00 |.....F..........|
00000030 01 00 06 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000040 80 00 29 1a e2 f3 0c 4e 4f 20 4e 41 4d 45 20 20 |..)....NO NAME |
00000050 20 20 46 41 54 33 32 20 20 20 0e 1f be 77 7c ac | FAT32 ...w|.|
00000060 22 c0 74 0b 56 b4 0e bb 07 00 cd 10 5e eb f0 32 |".t.V.......^..2|
00000070 e4 cd 16 cd 19 eb fe 54 68 69 73 20 69 73 20 6e |.......This is n|
00000080 6f 74 20 61 20 62 6f 6f 74 61 62 6c 65 20 64 69 |ot a bootable di|
00000090 73 6b 2e 20 20 50 6c 65 61 73 65 20 69 6e 73 65 |sk. Please inse|
000000a0 72 74 20 61 20 62 6f 6f 74 61 62 6c 65 20 66 6c |rt a bootable fl|
000000b0 6f 70 70 79 20 61 6e 64 0d 0a 70 72 65 73 73 20 |oppy and..press |
000000c0 61 6e 79 20 6b 65 79 20 74 6f 20 74 72 79 20 61 |any key to try a|
000000d0 67 61 69 6e 20 2e 2e 2e 20 0d 0a 00 00 00 00 00 |gain ... .......|
000000e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
000001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U.|
00000200 52 52 61 41 00 00 00 00 00 00 00 00 00 00 00 00 |RRaA............|
00000210 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
000003e0 00 00 00 00 72 72 41 61 ce e0 22 00 02 00 00 00 |....rrAa..".....|
000003f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U.|
00000400 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000800
mornagest@affreux:~$ ls -l /dev/disk/by-id
total 0
lrwxrwxrwx 1 root root 9 mai 17 19:46 ata-Hitachi_HTS542516K9SA00_071124BB0C00WGHA3N0C -> ../../sdc
lrwxrwxrwx 1 root root 10 mai 17 19:46 ata-Hitachi_HTS542516K9SA00_071124BB0C00WGHA3N0C-part1 -> ../../sdc1
lrwxrwxrwx 1 root root 10 mai 17 19:50 ata-Hitachi_HTS542516K9SA00_071124BB0C00WGHA3N0C-part2 -> ../../sdc2
lrwxrwxrwx 1 root root 10 mai 17 19:46 ata-Hitachi_HTS542516K9SA00_071124BB0C00WGHA3N0C-part3 -> ../../sdc3
lrwxrwxrwx 1 root root 9 mai 17 19:45 ata-ST1000DM003-1CH162_Z1D747QG -> ../../sdb
lrwxrwxrwx 1 root root 9 mai 17 19:44 ata-ST9250410ASG_5VG1F026 -> ../../sda
lrwxrwxrwx 1 root root 10 mai 17 19:45 ata-ST9250410ASG_5VG1F026-part1 -> ../../sda1
lrwxrwxrwx 1 root root 10 mai 17 19:45 ata-ST9250410ASG_5VG1F026-part2 -> ../../sda2
lrwxrwxrwx 1 root root 10 mai 17 19:45 ata-ST9250410ASG_5VG1F026-part5 -> ../../sda5
lrwxrwxrwx 1 root root 10 mai 17 19:45 ata-ST9250410ASG_5VG1F026-part6 -> ../../sda6
lrwxrwxrwx 1 root root 9 mai 17 19:45 ata-TSSTcorpDVD-ROM_TS-L333A -> ../../sr0
lrwxrwxrwx 1 root root 10 mai 17 19:45 dm-name-cryptswap1 -> ../../dm-0
lrwxrwxrwx 1 root root 10 mai 17 19:45 dm-uuid-CRYPT-PLAIN-cryptswap1 -> ../../dm-0
lrwxrwxrwx 1 root root 9 mai 17 19:44 wwn-0x5000c5001c33827b -> ../../sda
lrwxrwxrwx 1 root root 10 mai 17 19:45 wwn-0x5000c5001c33827b-part1 -> ../../sda1
lrwxrwxrwx 1 root root 10 mai 17 19:45 wwn-0x5000c5001c33827b-part2 -> ../../sda2
lrwxrwxrwx 1 root root 10 mai 17 19:45 wwn-0x5000c5001c33827b-part5 -> ../../sda5
lrwxrwxrwx 1 root root 10 mai 17 19:45 wwn-0x5000c5001c33827b-part6 -> ../../sda6
lrwxrwxrwx 1 root root 9 mai 17 19:45 wwn-0x5000c50064f331ef -> ../../sdb
lrwxrwxrwx 1 root root 9 mai 17 19:46 wwn-0x5000cca531d2b0e6 -> ../../sdc
lrwxrwxrwx 1 root root 10 mai 17 19:46 wwn-0x5000cca531d2b0e6-part1 -> ../../sdc1
lrwxrwxrwx 1 root root 10 mai 17 19:50 wwn-0x5000cca531d2b0e6-part2 -> ../../sdc2
lrwxrwxrwx 1 root root 10 mai 17 19:46 wwn-0x5000cca531d2b0e6-part3 -> ../../sdc3
mornagest@affreux:~$ sudo dd if=/dev/disk/by-id/ata-ST1000DM003-1CH162_Z1D747QG bs=512 count=1 | hexdump -C
00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
1+0 enregistrements lus
1+0 enregistrements écrits
512 bytes copied, 0,000186129 s, 2,8 MB/s
*
00000200