Primary Database
Oracle Release:	Oracle10g Release 2 - (10.2.0.3.0)
Machine Name:	vmlinux3.idevelopment.info
Operating System:	Red Hat Linux 4 - (CentOS 4.5)
Oracle SID:	TESTDB
Instance Service Names:	TESTDB.IDEVELOPMENT.INFO
TNS Service Name:	TESTDB_VMLINUX3.IDEVELOPMENT.INFO
Standby Database
Oracle Release:	Oracle10g Release 2 - (10.2.0.3.0)
Machine Name:	vmlinux4.idevelopment.info
Operating System:	Red Hat Linux 4 - (CentOS 4.5)
Oracle SID:	TESTDB
Instance Service Names:	TESTDB.IDEVELOPMENT.INFO
TNS Service Name:	TESTDB_VMLINUX4.IDEVELOPMENT.INFO

The rsh daemon on the standby database server validates UNIX users using the /etc/hosts.equiv file or the .rhosts file found in the user's (oracle's) home directory.

The use of rcp (and any other of the r* commands) is not required for normal Data Guard operation. rcp, however, does expedite the initial copying of database files from the primary host to the standby host! After copying all database files from the primary database server to the standby database server, this feature can be disabled.

Before configuring the .rhosts file, we must first make sure that we have the rsh RPMs installed on each node in the RAC cluster:

# rpm -q rsh rsh-server
rsh-0.17-25.3
rsh-server-0.17-25.3

If rsh is not installed, run the following command from the CD where the RPM is located: # su - # rpm -ivh rsh-0.17-25.3.rpm rsh-server-0.17-25.3.rpm

To enable the "rsh" service, the "disable" attribute in the /etc/xinetd.d/rsh file must be set to "no" and xinetd must be reloaded. This can be done by running the following commands on both nodes in the Data Guard configuration:

# su -
# chkconfig rsh on
# chkconfig rlogin on
# chkconfig rsync on
# chkconfig rexec on
# service xinetd reload
Reloading configuration: [  OK  ]

Here is a copy of the .rhosts file I have configured on both of my Linux servers for the oracle user account. This file should reside in the $HOME directory for the oracle user account:

Example .rhosts File

+vmlinux3.idevelopment.info oracle +vmlinux4.idevelopment.info oracle

Before attempting to test the rsh command, ensure that you are using the correct version of rsh. By default, Red Hat Linux puts /usr/kerberos/sbin at the head of the $PATH variable. This will cause the Kerberos version of rsh to be executed. I will typically rename the Kerberos version of rsh so that the normal rsh command will be used. Use the following: # su - # which rsh /usr/kerberos/bin/rsh # mv /usr/kerberos/bin/rsh /usr/kerberos/bin/rsh.original # mv /usr/kerberos/bin/rcp /usr/kerberos/bin/rcp.original # mv /usr/kerberos/bin/rlogin /usr/kerberos/bin/rlogin.original # which rsh /usr/bin/rsh

For security reasons, the permissions of the .rhosts file should be 600 and owned by the "oracle" user account. If instead, you are using a global /etc/hosts.equiv file, it should be owned by root and the permissions be set to 600. In fact, some systems will only honor the content of this file if the owner of this file is root and the permissions are set to 600.

$ chmod 600 ~/.rhosts
$ ls -l ~/.rhosts
-rw-------  1 oracle dba 0 Jun 21 17:08 /u01/app/oracle/.rhosts

After configuring the .rhost file on both computers, I like to perform a simple test from each machine to ensure that the configuration is valid:

FROM vmlinux3 MACHINE

    $ id
    uid=175(oracle) gid=115(dba) groups=115(dba) context=user_u:system_r:unconfined_t

    $ rsh vmlinux4 hostname
    vmlinux4


FROM vmlinux4 MACHINE

    $ id
    uid=175(oracle) gid=115(dba) groups=115(dba) context=user_u:system_r:unconfined_t

    $ rsh vmlinux3 hostname
    vmlinux3