Thursday, November 17, 2005

Upgrade to RedHat AS 4.0

Upgrading to RedHat 4.0 introduces some new challenges. With the switch to the 2.6 linux kernel the udev device filesystem was introduced. By default the udev device tree does not support raw devices anymore. Luckily it is still supported with the Redhat distribution. It can be configured in the old way with the rawdevices service configuration.

To check if it is currently enabled run the following command:
# chkconfig --list
and search for rawdevices. If it is not enabled yet add the rawdevices service with
# chkconfig --level 345 rawdevices on.
Afterwards start the service in the usual way with service start rawdevices.

The next step is to set the permissions correctly. especially for Oracle database files, OCR and the voting disks it is important to set the correct file permissions. Setting the permissions on the raw devices directly will only work partially. As soon as the node gets rebooted the raw devives will be reset tohave root privileges. To make the change final it is necessary to edit the file /etc/udev/permissions.d/50-udev.permissions. Search for the substring "raw" in this file. You will find something like
and change the line to
For the future it makes sense to no longer use /dev/raw. There are plans to completely de-support it with kernel version 2.7.

No comments: