If the SAN-attached XIV volumes are needed early in the Linux boot process, include the HBA driver into the Initial RAM file system (initramfs) image. You must include this driver, for example, if all or part of the system is on these volumes. The initramfs allows the Linux boot process to provide certain system resources before the real system disk is set up.
Linux distributions contain a script that is called mkinitrd that creates the initramfs image automatically. They automatically include the HBA driver if you already used a SAN-attached disk during installation. If not, you must include it manually. The ways to tell mkinitrd to include the HBA driver differ depending on the Linux distribution used.
SUSE Linux Enterprise Server
Kernel modules that must be included in the initramfs are listed in the file
/etc/sysconfig/kernel on the line that starts with INITRD_MODULES. The order that they show up on this line is the order that they are loaded at system startup (Example 3-6).
Example 3-6 Telling SLES to include a kernel module in the initramfs x3650lab9:~ # cat /etc/sysconfig/kernel
...
# This variable contains the list of modules to be added to the initial
# ramdisk by calling the script "mkinitrd"
# (like drivers for scsi-controllers, for lvm or reiserfs)
#
INITRD_MODULES="thermal aacraid ata_piix ... processor fan jbd ext3 edd qla2xxx"
...
After you add the HBA driver module name to the configuration file, rebuild the initramfs with the mkinitrd command. This command creates and installs the image file with standard settings and to standard locations as illustrated in Example 3-7.
Example 3-7 Creating the initramfs x3650lab9:~ # mkinitrd
Kernel image: /boot/vmlinuz-2.6.32.12-0.7-default Initrd image: /boot/initrd-2.6.32.12-0.7-default
Root device: /dev/disk/by-id/scsi-SServeRA_Drive_1_2D0DE908-part1 (/dev/sda1)..
Resume device: /dev/disk/by-id/scsi-SServeRA_Drive_1_2D0DE908-part3 (/dev/sda3) Kernel Modules: hwmon thermal_sys ... scsi_transport_fc qla2xxx ...
Considerations:
Installing a Linux system on a SAN-attached disk does not mean that it is able to start from it. Usually you must complete more steps to configure the boot loader or boot program.
You must take special precautions about multipathing if you want to run Linux on SAN-attached disks.
For more information, see 3.5, “Boot Linux from XIV volumes” on page 129.
Tip: The initramfs was introduced years ago and replaced the Initial RAM Disk (initrd).
People sometimes say initrd when they actually mean initramfs.
(module qla2xxx.ko firmware /lib/firmware/ql2500_fw.bin) (module qla2xxx.ko ...
Features: block usb resume.userspace resume.kernel Bootsplash: SLES (800x600)
30015 blocks
If you need nonstandard settings, for example a different image name, use parameters for mkinitrd. For more information, see the man page for mkinitrd on your Linux system.
Red Hat Enterprise Linux 5 (RH-EL5)
Kernel modules that must be included in the initramfs are listed in the file
/etc/modprobe.conf. The order that they show up in the file is the order that they are loaded at system startup as seen in Example 3-8.
Example 3-8 Telling RH-EL to include a kernel module in the initramfs [root@x3650lab9 ~]# cat /etc/modprobe.conf
After you add the HBA driver module to the configuration file, rebuild the initramfs with the mkinitrd command. The Red Hat version of mkinitrd requires as the following information as parameters (Example 3-9):
The name of the image file to create
The location of the image file
The kernel version that the image file is built for Example 3-9 Creating the initramfs
[root@x3650lab9 ~]# mkinitrd /boot/initrd-2.6.18-194.el5.img 2.6.18-194.el5
If the image file with the specified name exists, use the -f option to force mkinitrd to overwrite the existing one. The command shows more detailed output with the -v option.
You can discover the kernel version that is running on the system with the uname command as illustrated in Example 3-10.
Example 3-10 Determining the kernel version [root@x3650lab9 ~]# uname -r
2.6.18-194.el5
Red Hat Enterprise Linux 6 (RH-EL6)
Dracut is a new utility for RH-EL6 that is important to the boot process. In previous versions of RH-EL, the initial RAM disk image preinstalled the block device modules, such as for SCSI or RAID. The root file system, on which those modules are normally located, can then be accessed and mounted.
With Red Hat Enterprise Linux 6 (RH-EL6) systems, the dracut utility is always called by the installation scripts to create an initramfs. This process occurs whenever a new kernel is installed by using the Yum, PackageKit, or Red Hat Package Manager (RPM).
On all architectures other than IBM i, you can create an initramfs by running the dracut command. However, you usually do not need to create an initramfs manually. This step is automatically completed if the kernel and its associated packages are installed or upgraded from the RPM packages that are distributed by Red Hat.
Verify that an initramfs corresponding to your current kernel version exists and is specified correctly in the grub.conf configuration file by using the following procedure:
1. As root, list the contents in the /boot/ directory.
2. Find the kernel (vmlinuz-<kernel_version>) and initramfs-<kernel_version> with the most recent version number, as shown in Figure 3-1.
Figure 3-1 Red Hat 6 (RH-EL6) display of matching initramfs and kernel
Optionally, if your initramfs-<kernel_version> file does not match the version of the latest kernel in /boot/, generate an initramfs file with the dracut utility. Starting dracut as root, without options generates an initramfs file in the /boot/ directory for the latest kernel present in that directory. For more information about options and usage, see man dracut and man dracut.conf.
On IBM i servers, the initial RAM disk and kernel files are combined into a single file that is created with the addRamDisk command. This step is completed automatically if the kernel and its associated packages are installed or upgraded from the RPM packages that are
distributed by Red Hat. Therefore, it does not need to be run manually.
To verify that it was created, use the command ls -l /boot/ and make sure that the
/boot/vmlinitrd-<kernel_version> file exists. The <kernel_version> must match the version of the installed kernel.
3.2.3 Determining the WWPN of the installed HBAs
To create a host port on the XIV that can map volumes to an HBA, you need the WWPN of the HBA. The WWPN is shown in sysfs, a Linux pseudo file system that reflects the installed hardware and its configuration. Example 3-11 shows how to discover which SCSI host instances are assigned to the installed FC HBAs. You can then determine their WWPNs.
Example 3-11 Finding the WWPNs of the FC HBAs [root@x3650lab9 ~]# ls /sys/class/fc_host/
# cat /sys/class/fc_host/host1/port_name 0x10000000c93f2d32
# cat /sys/class/fc_host/host2/port_name 0x10000000c93d64f5
Map volumes to a Linux host as described in 1.4, “Logical configuration for host connectivity”
on page 36.
3.2.4 Attaching XIV volumes to an Intel x86 host using the Host Attachment Kit
You can attach the XIV volumes to an Intel x86 host by using a Host Attachment Kit.