HP 3PAR RedHat and Oracle Linux Implementation Guide

You can use the following commands to configure multipath devices:
• multipath inspects Linux devices to see if there are multiple paths to the same device and
communicates to the kernel device-mapper to set up a device map (dm) device for the device
and is responsible for the path coalescing and device map creation.
• The multipathd daemon checks path health and will reconfigure the multipath map whenever
a path comes up or goes down so as to maintain correctly the path mapping state.
• kpartx reads partition tables on specified devices and creates device maps over partition
segments that are detected.
Device-mapper also depends on the udev and sysfsutils filesystem packages. udev is a user
space process which dynamically manages the creation of devices under the /dev/ filesystem.
The sysfsutils package exports the view of the system hardware configuration to udev
userspace process for device node creation. These packages must be present on the system.
For example:
# rpm -qa | grep udev
udev-039-10.19.el4
# rpm -qa | grep sysfs
sysfsutils-devel-1.2.0-1
sysfsutils-1.2.0-1
In RHEL 5.4, the following packages appear after installation:
# rpm -qa | grep udev
udev-095-14.21.el5
# rpm -qa | grep sysfs
libsysfs-2.0.0-6
sysfsutils-2.0.0-6
If /usr is a separate partition and is not part of the root (/) partition in the installed RHEL Operating
System, then copy the shared library libsysfs.so and create the required sysmlinks from
the /usr/lib directory to the /lib directory.
The following examples show partitions for 32-bit and 64-bit operating systems:
• On a 32-bit installed operating system:
# cp /usr/lib/libsysfs.so.1.0.2 /lib/
# ln -s /lib/libsysfs.so.1.0.2 /lib/libsysfs.so.1
# ln -s /lib/libsysfs.so.1 /lib/libsysfs.so
• On 64-bit installed operating system:
# cp /usr/lib64/libsysfs.so.1.0.2 /lib64/
# ln -s /lib64/libsysfs.so.1.0.2 /lib64/libsysfs.so.1
# ln -s /lib64/libsysfs.so.1 /lib64/libsysfs.so
CAUTION: If /usr is a separate partition, there will be a system hang during bootup when
multipath starts and cannot find the shared library libsysfs.so.1 because /usr partition gets
mounted at the later stage of the boot process. So, copying the shared library libsysfs.so.1
to the /lib directory will resolve the issue.
Setting Up Multipathing Software 49