Chapter 1. Kernel

Enhanced SCSI Unit Attention Handling

The kernel in Red Hat Enterprise Linux 6.6 has been enhanced to enable user space to respond to certain SCSI Unit Attention conditions received from SCSI devices via the udev event mechanism. The supported Unit Attention conditions are:
  • 3F 03 INQUIRY DATA HAS CHANGED
  • 2A 09 CAPACITY DATA HAS CHANGED
  • 38 07 THIN PROVISIONING SOFT THRESHOLD REACHED
  • 2A 01 MODE PARAMETERS CHANGED
  • 3F 0E REPORTED LUNS DATA HAS CHANGED
The default udev rules for the supported Unit Attention conditions are provided by the libstoragemgmt RPM package. The udev rules are located in the /lib/udev/rules.d/90-scsi-ua.rules file.
The default rules handle the REPORTED LUNS DATA HAS CHANGED unit attention. Additional example rules are present to enumerate the other events that the kernel can generate. Note that the default rules do not automatically remove logical unit numbers (LUNs) that are no longer present on the SCSI target.
Because SCSI Unit Attention conditions are only reported in response to a SCSI command, no conditions are reported if no commands are actively being sent to the SCSI device.
The default behavior can be customized by modifying or removing the udev rules. If the libstoragemgmt RPM package is not installed, the default rules are not present. If no udev rules are present for those events, no action is taken, but the events themselves are still generated by the kernel.

Open vSwitch Kernel Module

Red Hat Enterprise Linux 6.6 includes the Open vSwitch kernel module as an enabler for Red Hat's layered products. Open vSwitch is supported only in conjunction with products that contain the accompanying user-space utilities. Please note that without these required user-space utilities, Open vSwitch will not function and cannot be enabled for use. For more information, please refer to the following Knowledge Base article: https://access.redhat.com/knowledge/articles/270223.