Changes to Configuration Files¶
Changes to Red Hat Configuration Files¶
An installation of Red Hat sets a default configuration optimized for a stand-alone server. Installing ClusterWare on a Red Hat installation changes some of these default configuration parameters to better support a cluster. The following sections describe the changes the ClusterWare installation automatically makes to the Red Hat configuration. Any of these may be reversed; however, reversing them may adversely affect the operation of the ClusterWare cluster.
/etc/grub.confhas been modified.
After ClusterWare has been installed, the default boot becomes the newest ClusterWare kernel.
NFS Services default configuration has been modified.
By default, Red Hat configures NFS to "off" for security reasons. However, most cluster applications require that at least the home directory of the master node be accessible to the compute nodes. NFS services on the master are set with the default to "on" for run levels 3, 4, and 5.
The default out-of-box chkconfig for NFS on RHEL6 is as follows:
[root@scyld ~]# chkconfig --list nfs nfs 0:off 1:off 2:off 3:off 4:off 5:off 6:off
ClusterWare has changed the default to the following:
[root@scyld ~]# chkconfig --list nfs nfs 0:off 1:off 2:off 3:on 4:on 5:on 6:off
To get NFS to mount directories from the master to the compute nodes, the file
/etc/exportsneeds one entry per line for each file system to export from the master to the compute nodes (the RHEL-MAJOR default is a blank/non-existent file). ClusterWare creates this file if it didn't already exist, and adds several new entries of the form:
The export for
/homefrom the master is configured with an accessMode of
rw(read-write) and a syncMode of
syncby default for data reliability reasons, and the non-/home directories are exported
ro(read-only) for security reasons and
asyncfor performance reasons.
See the ClusterWare Release Notes for details about which directories are added by Scyld.
/etc/sysconfig/sysloghas been modified.
Compute nodes will forward messages to the master node's syslogd daemon, which places them in
/var/log/messages. In order for this to function correctly, ClusterWare modifies the
/etc/sysconfig/syslogfile by adding the
-roption to the
SYSLOGD_OPTIONS="-m 0 -r"
Possible Changes to ClusterWare Configuration Files¶
A clean install of ClusterWare introduces various ClusterWare configuration
files that include default settings that a local sysadmin may choose to
modify. A subsequent upgrade from one ClusterWare release to a newer
release will avoid replacing these potentially modified files. Instead,
an update installs a new version of the default file as a file of the
CWconfigFile.rpmnew. Therefore, after a ClusterWare upgrade,
the sysadmin is encouraged to compare each such existing
with the new default version to ascertain which of the new default entries
are appropriate to manually merge into the preexisting
ClusterWare specifies additional libraries for compute nodes that may help various applications and scripts execute out-of-the-box
ClusterWare specifies additional
/devdevices and NFS-mounted directories for compute nodes that may help various applications and scripts execute out-of-the-box.