In this Document

Applies to:

Goal

Real Application Clusters (RAC) requires special ownership (owner, group and permissions) for the OCR (Oracle Cluster Registry) and Voting devices on Linux.

In the 2.6 kernel, the UDEV system is the default method through which the kernel controls the creation of the special files that represent resources such as block devices. 
In Oracle 10g RAC, where raw devices are a mandatory requirement for use by CRS, raw devices require specific ownership and permissions.  Prior to UDEV, device nodes
could be created and their access permissions persistently set using the mknod(1) utility; the UDEV facility dynamically recreates the /dev content each reboot, preventing this approach. 
The solution is to add UDEV rules to set these attributes automatically.   The configuration file syntax for UDEV in SLES10, RHEL5 and OEL5 have vary slightly compared depending on the software version.

For SuSE Linux Enterprise Server 10 (SLES10), UDEV rules for raw device permission setting should be placed into rule files under the /etc/udev/rules.d/ directory. 
The files are processed in ls(1) order, with default system rules contained in the 50-udev-default.rules file.

 From SLES10, there is no separation between rules for creating devices and rules for device permissions - both  are now set from the same rule file.
In order to alter the permissions for raw devices, create a permission rule file that sets the appropriate device permissions in the rules.d/ directory,
so that it is processed before the default rules:

Solution

1.  Create The New UDEV Rules

Choose one of the following methods, depending upon your RAC version.

1.1  Create UDEV Permission Rule Prior Up-To Version 11.1.0.7

Create a custom UDEV permission rule file (for example, /etc/udev/rules.d/99-raw.rules) and ensure the file name lists after the default 50-xxx.rules file. 
The filename must end in ".rules" to be recognized.

Add the required raw device ownership and permissions, for example:

1.2  Create UDEV Permission Rule For Version 11.2 And Later

Create a UDEV rules file for the Oracle ASM devices, setting permissions to read/write for the group and owner (0660) for the installation
owner and the group whose members are to be administrators of the grid infrastructure software.

For example, using the installation owner grid and using a role-based group configuration, with the OSASM group asmadmin:

 For RHEL5/OL5/OEL5,

 For RHEL6/OL6:

Copy this rules.d/file to all other nodes on the cluster. For example:

2. Restart The UDEV Service

Restart the UDEV service as follows. Then verify the devices now reflect their intended ownership and permissions:

On SLES10:

On RHEL5/OEL5/OL5:

On RHEL6/OL6:

3. Additional UDEV information

For additional information on UDEV, including how to manage multiple partitions, refer to the following article:

      Using udev with Oracle Architecture (RAC & ASM) - Red Hat 4.0 Note:371814.1

References