Multiple LUNs (scsi_mod) and RHEL4

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I'm trying to kickstart a machine, and partition disks on 3 fibre
attached LUNs (lpfc/emulex), but the installer only sees the first one
(/dev/sda), and not the other two (/dev/sdb, /dev/sdc)

Out of the box, the RHEL4 initrd is configured to only discover a
single scsi LUN.  In order to fix this, you have to use a custom
initrd:

# echo "options scsi_mod max_luns=xx" >> /etc/modprobe.conf
# mkinitrd -f
# reboot
(where xx > 1)

This works fine *after* the box is installed, but is there a way to
make this work during the kickstart install?  I tried using some %pre
scripts, but it didn't work:

---ks.cfg---
...
%pre
rmmod scsi_mod
modprobe scsi_mod max_luns=128
...
%post
echo "options scsi_mod max_luns=255" >> /etc/modprobe.conf
mkinitrd -f -v
---ks.cfg---

Howto: Linux see new fiber channel attached disk LUNs without rebooting

Posted in Linux

Q. How do I force fdisk to see new fiber channel attached disk LUNs without rebooting my Linux server or system?

A. Hot swapping or hot plugging is the ability to remove and replace components of a machine, usually a computer, while it is operating. Once the appropriate software is installed on the computer, a user can plug and unplug the component without rebooting.

You can add new SCSI device to a Linux system through SCSI hotplug mechanism.

Type the following command as root user:

$ echo "scsi add-single-device 1 2 3 4">/proc/scsi/scsi

Where,

• 1 - HBA number
• 2 - channel id on the HBA
• 3 - SCSI ID of the new device
• 4 - LUN of the new device

You need to replace 1,2,3,4 with actual values or parameters as per above list.

http://www.cyberciti.biz/faq/howto-linux-see-new-fiber-channel-attached-disk-luns-without-rebooting/