Installation guide

# initrd /initrd-[generic-]version.img
#boot=/dev/hda
default=0
timeout=5
serial --unit=0 --speed=115200
terminal --timeout=5 serial console
title Red Hat Enterprise Linux Server (2.6.32-193.el6.x86_64)
root (hd0,0)
kernel /vmlinuz-2.6.32-193.el6.x86_64 ro
root=/dev/mapper/vg_doc01-lv_root console=ttyS0,115200n8 acpi=off
initrd /initramrs-2.6.32-131.0.15.el6.x86_64.img
In this example, acpi= o ff has been appended to the kernel boot command line — the line
starting with " kernel /vmlinuz-2.6.32-193.el6.x86_64.img".
2.6. Considerat ions for Configuring HA Services
You can create a cluster to suit your needs for high availability by configuring HA (high-availability)
services. The key component for HA service management in the Red Hat High Availability Add-On,
rg manager, implements cold failover for off-the-shelf applications. In the Red Hat High Availability
Add-On, an application is configured with other cluster resources to form an HA service that can fail
over from one cluster node to another with no apparent interruption to cluster clients. HA-service
failover can occur if a cluster node fails or if a cluster system administrator moves the service from
one cluster node to another (for example, for a planned outage of a cluster node).
To create an HA service, you must configure it in the cluster configuration file. An HA service
comprises cluster resources. Cluster resources are building blocks that you create and manage in the
cluster configuration file — for example, an IP address, an application initialization script, or a Red
Hat GFS2 shared partition.
To ensure data integrity, only one node can run a cluster service and access cluster-service data at
a time. You can specify failover priority in a failover domain. Specifying failover priority consists of
assigning a priority level to each node in a failover domain. The priority level determines the failover
order — determining which node that an HA service should fail over to. If you do not specify failover
priority, an HA service can fail over to any node in its failover domain. Also, you can specify if an HA
service is restricted to run only on nodes of its associated failover domain. When associated with an
unrestricted failover domain, an HA service can start on any cluster node in the event no member of
the failover domain is available.
Figure 2.1, “Web Server Cluster Service Example” shows an example of an HA service that is a web
server named "content-webserver" . It is running in cluster node B and is in a failover domain that
consists of nodes A, B, and D. In addition, the failover domain is configured with a failover priority to
fail over to node D before node A and to restrict failover to nodes only in that failover domain. The HA
service comprises these cluster resources:
IP address resource — IP address 10.10.10.201.
An application resource named "httpd-content" — a web server application init script
/etc/i ni t. d /httpd (specifying httpd).
A file system resource — Red Hat GFS2 named "gfs2-content-webserver".
⁠Chapt er 2 . Before Configuring t he Red Hat High Availabilit y Add- O n
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