6. How do i know the BIOS number for my SCSI disks
The contribution from Marc Tanguy (mtanguy@ens.uvsq.fr), 2001-09-27
6.1 The theory
Actually, it exists two ways to know it :
If you have an adaptec scsi card (2940u2, 29160, 39160), you simply use the 'diagnose' mode (using BIOS v3.10.0 recommended). It must be activated in the scsi card BIOS menu. Then you just have to wait and see something like :
| ... | ID | LUN | Vendor | Product | Rev | Size | Sync | Bus | HD# |
| ... | 0 | 0 | QUANTUM | ATLAS10K2 | DDD6 | 17GB | 160 | 16 | 80h |
| ... | 1 | 0 | QUANTUM | ATLAS10K2 | DDD6 | 17GB | 160 | 16 | 81h |
| ... | 2 | 0 | IBM | DDRS | DC1B | 4GB | 80 | 16 | 82h |
| ... | 3 | 0 | IBM | DNES | SAH0 | 9GB | 80 | 16 | 83h |
If you don't own an adaptec card, you have to know what is the 'booting' disk (usually ID 0, but not necessary, it can be defined in the scsi card BIOS) where LILO is going to be found and start : this is the first disk so it has number 0x80. Then it's very simple, the BIOS follows the IDs.
By example :
ID 0 -> boot -> 0x80 ID 1 -> empty ID 2 -> disk -> 0x81 ID 3 -> disk -> 0x82
or
ID 0 -> disk -> 0x81 ID 1 -> empty ID 2 -> disk -> 0x82 ID 3 -> boot -> 0x80 ID 4 -> disk -> 0x83
This part doesn't care at all of what is installed on the scsi drives. But you should note that if you use an ID higher than the SCSI adapter it c an be a problem. So you should always try to set the SCSI adapter ID after the SCSI devices IDs.
6.2 How to swap linux and NT booting ?
OK, but NT must be the first disk to boot, so i want it in 0x80, but i already have LILO and a full ext2 only drive on 0x80 and my NT drive is in 0x83. How can i 'swap' linux and NT ? This a very easy : you just have to tell BIOS that NT drive is now 0x80 and the Linux drive is 0x83.
other=/dev/sdd1
label=nt
map-drive = 0x83
to = 0x80
map-drive = 0x80
to = 0x83
This change will produce a warning :
Warning: BIOS drive 0x8? may not be accessible
but if you know what you are doing it will run without problem.
I used it on this configuration which has a Red Hat Linux 7.1 and a Windows 2000 Pro :
Name Flags Part Type FS Type [Label] Size (MB) Disk Drive: /dev/sda - 0x80 sda1 Boot Primary Linux ext2 [/boot] 24.68 sda2 Primary Linux Swap 139.83 sda3 Primary Linux ext2 [/usr] 3150.29 sda4 Primary Linux ext2 [/home] 15044.04 Disk Drive: /dev/sdb - 0x81 sdb1 Primary Linux Swap 139.83 sdb2 Primary Linux ext2 [/] 3150.29 sdb3 Primary Linux ext2 [/opt] 1052.84 sdb4 Primary Linux ext2 [/public] 14015.88 Disk Drive: /dev/sdc - 0x82 sdc1 Primary Linux ext2 [/var] 1052.84 sdc2 Primary Linux ext2 [/tmp] 106.93 sdc3 Primary Linux ext2 [/cache] 1052.84 sdc4 Primary Linux ext2 [/chroot] 2352.44 Disk Drive: /dev/sdd - 0x83 sdd1 Boot Primary NTFS [WINDOWS_2000] 9162.97
My full /etc/lilo.conf :
boot=/dev/sda map=/boot/map install=/boot/boot.b prompt default=Linux read-only compact image=/boot/vmlinuz label=Linux root=/dev/sdb2 other=/dev/sdd1 label=Windows map-drive = 0x83 to = 0x80 map-drive = 0x80 to = 0x83
6.3 Miscellaneous
I just plugged a new scsi drive, and now LILO refuse to boot, what's going on ?
When you plug a disk, you must be careful with the IDs. If you add a drive between two already plugged disks the BIOS numbers are changed :
Before ----> After
scsi id - - BIOS id scsi id - - BIOS id
ID 0 - disk - 0x80 ID 0 - disk - 0x80
ID 1 - empty ID 1 - new disk - 0x81
ID 2 - disk - 0x81 ID 2 - disk - 0x82 !!
If you change the BIOS ids, you have to re-evaluate them.
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