Exalogic includes a tool called DCLI (Distributed Command Line Interface) that can be used to run the same commands on all or a subset of compute nodes in parallel. This saves a lot of time and helps avoid the sorts of silly errors that often occur when running a command over and over again. DCLI is a tool that originally came with Exadata (as documented in the Oracle Exadata Storage Server Software User's Guide - E13861-05 chapter 9), and is now incorporated into the new Exalogic product too. It is worth noting that if you are ever involved in performing the initial configuration of a new Exalogic rack, using OneCommand to configure the Exalogic's networking, then under the covers OneCommand will be using DLCI to perform a lot of its work.
Introduction to Exalogic's DCLI
The Oracle Enterprise Linux 5.5 based factory image running on each Exalogic compute node has the exalogic.tools RPM package installed. This contains the DCLI tool in addition to other useful Exalogic command line utilities. Running 'rpm -qi exalogic.tools' on a compute node shows the following package information:
Name : exalogic.toolsWhen you run 'rpm -ql exalogic.tools' you will see that the set of command line utilities are all placed in a directory at '/opt/exalogic.tools'. Specifically, the DCLI tool is located at '/opt/exalogic.tools/tools/dcli'.
Version : 22.214.171.124
Release : 1.0
Now run the DCLI command with the '-k' option as shown below which pushes the current user's SSH public key to each other compute node's '.ssh/authorized_keys' file to establish SSH Trust. You will again be prompted to enter the password for each compute node, but this will be the last time you will need to. With the '-k' option, each compute node is contacted sequentially rather than in parallel, to give you chance to enter the password for each node in turn.
You can then run the original date-time test again, to satisfy yourself that SSH Trust and User Equivalence is indeed established between the master compute node and each other compute node and that no passwords are prompted for.
# /opt/exalogic.tools/tools/dcli -t -g nodeslist /bin/date
Now lets have a look at some examples common DCLI commands you might need to issue for your new Exalogic system.
# /opt/exalogic.tools/tools/dcli -t -g nodeslist groupadd -g 500 oracle
# /opt/exalogic.tools/tools/dcli -t -g nodeslist useradd -g oracle -u 500 oracle
echo welcome1 | passwd root --stdin
echo welcome1 | passwd oracle --stdin
# chmod u+x setpasswds.scl
# /opt/exalogic.tools/tools/dcli -t -g nodeslist -x setpasswds.scl
# /opt/exalogic.tools/tools/dcli -t -g nodeslist chown -R oracle:oracle /u01/common/general
# vi addmount.scl
cat >> /etc/fstab << EOF
el01sn-priv:/export/common/general /u01/common/general nfs rw,bg,hard,nointr,rsize=131072,wsize=131072,tcp,vers=3 0 0
# chmod u+x addmount.scl
# /opt/exalogic.tools/tools/dcli -t -g nodeslist mount /u01/common/general
In the default Exalogic set-up, DCLI executes as root user when issuing all of its commands regardless of what OS user's shell you use to enter the DCLI command from. Although root access is often necessary for creating things like OS users, groups and mount points, it is not desirable if you just want to use DCLI to execute non-privileged commands under a specific OS user on all computes nodes. For example, as a new 'coherence' OS user, you may want the ability to run a script that starts a Coherence Cache Server instance on every one of the compute nodes in the Exalogic rack, in one go, to automatically join the same Coherence cluster.