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Configuring the System to Boot From SAN Using Persistent Names
To use a persistent name for a boot device (SLES 11 SP1):
1. In /boot/grub/menu.lst, find the kernel line for the default boot. For example:
kernel /boot/vmlinuz root=/dev/sda2 vga=0x314
2. Find the persistent name for the root partition (following “root=” on the kernel line) by using the
instructions in “Using udev to Discover Logical to Physical Mappings for sd Devices” on
page 17.
3. In the same file, /boot/grub/menu.lst, replace the text after “root=” with the partition's persistent
name. For example:
kernel /boot/vmlinuz root=/dev/disk/by-id/scsi-32000000c5005d6e6-part2
vga=0x314
4. Change any mounts listed in /etc/fstab which refer to this root partition by either it's /dev/sd
name or a file system LABEL to use the persistent name as well.
To use a persistent name for a boot device (RHEL 6):
1. In /boot/grub/grub.conf, find the kernel line for the default boot. For example:
kernel /boot/vmlinuz -<kernel version> ro root=/dev/sda2
2. Find the persistent name for the root partition (following "root=" on the kernel line) by using the
instructions in “Using udev to Discover Logical to Physical Mappings for sd Devices” on
page 17.
3. In the same file, /boot/grub/menu.lst, replace the text after "root=" with the partition's persistent
name. For example:
kernel /boot/vmlinuz -<kernel version> ro root=/dev/disk/by-id/scsi32000000c5005d6e6-part2
4. Change any mounts listed in /etc/fstab which refer to this root partition by either it's /dev/sd
name or a file system LABEL to use the persistent name as well.
Using udev with st Devices
The udev rules for tape devices are the same for disk devices. There must be a unique ID that persists
across initiator reboots and persists regardless of discovery order.
Another thing to consider is whether or not the tape device is one of many SCSI tape devices residing
behind an FC controller, or if it is an FC-Tape device. If it an FC-Tape device, then the WWPN is unique
and can be used to create the persistent name. In fact, the scsi_id program should return this as the
unique identifier with a single digit prefix.
If the FC controller has multiple SCSI tape devices behind it, the WWPN is not unique and the persistent
name must use multiple information elements to build the unique ID.
Below are examples of each scenario. The first example is that of an FC-Tape device. This example
uses SCSI generic (sg) rather than the SCSI tape driver.
[root@localhost ~]# scsi_id -g -s /sys/class/scsi_generic/sg0
350060b000029b592
The value returned has a leading prefix of 3. This value is the NAA type and what follows is the
controller's WWPN.
Below is an example of the same tape device and a scsi_id call. The response is the same.
[root@localhost ~]# scsi_id -g -s /sys/class/scsi_tape/nst0
350060b000029b592
In both examples, -g was needed because the vendor and model for this tape device were not in /etc/
scsi_id.config.
Emulex Drivers for Linux User Manual: Configuration
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