Node/Host Setup

Today I want to begin to show you how to step LCMC.  I discovered LCMC when I was looking for a GUI that would aid me in creating a Linux Based High Availability SAN.  LCMC is powerful and has the ability to make a cluster of most systems in Linux (MySQL, Apache to name a few).  To get LCMC to work with SCST, there are a few things to add and adjust so that LCMC can stop and start the required SCST services in Linux.  LCMC requires that SSH is installed on the Hosts that will be managed.  Let’s start with the basic installation…LCMC Start Page

  When you first launch LCMC, you will be presented with a basic screen which will allow you to add the hosts which you will use to create your cluster.  You’ll want to hit the button “Add Host / Wizard” which will prompt you for the information for your first node.AddHost1

 You will need to enter the Host FQDN (if you use a hostfile) or IP address, the SSH port the computer will respond to (22 is default) and a username to log into.  If you select “root”, the “Use sudo:” box will be greyed out.  It’s recommended that you create a user and setup “Use sudo:” for added security.  It should be noted that LCMC uses text based commands it send via a SSH connection to perform the tasks you would normally do via a command line.  When you are done, hit “Next”AddHost2LCMC will next attempt a DNS lookup of the hostname if you’ve entered one.  Hit “Next”.AddHost3You will now be presented with a dialog to accept the hostkey for the SSH connection.  This popup should only show up the first time you attempt to connect to the host..  Hit “Yes”.AddHost4LCMC will then log into the Host and run a query for any installed applications.  Hit “Next” when done.AddHost5

You should then have a window which indicates which Linux Distribution LCMC detected.  Hit “Next”.AddHost6

 You will now be presented with the package selection window shown above.  This is where you tell LCMC which application sets to install.  You can install either Pcmk/Heartbeat or Pcmk/Corosync (but not both).  Once you install one set, the other “Install” button gets greyed out.  I’ve setup Pcmk/Heartbeat so my instructions in up-coming modules will be based on that.AddHost7 When you hit install the above window will display the progress of the installation and return you to the package selection window.  You can elect to install Drbd at this point.  I would install it anyway even if you are following the instructions to build a Gluster iSCSI Head Node Unit.  Drbd is rather small and it doesn’t get in the way if you don’t configure it.  This way you don’t get any reds and the “Next” button won’t be greyed out.  If you choose to install Drbd, you’ll get a similar windows showing the progress of the installation.AddHost8Once you are done, the package selection window should report what version of the selected packages were installed.AddHost9Hit next and you are done with installing the required software packages on this host.
AddHost10 You will now perform the process again for the 2nd Host in the cluster.  Repeat the steps outlined above and setup the next host.  When you are done you will be brought back to the above window.  The next step will be in setting up the cluster itself.

Cluster Setup

When I left off last time, I showed you how to install Hosts into an LCMC setup.  When you finish the 2nd host install, you’ll be prompted to create a new Cluster using the Cluster Wizard.  Select an appropriate name and press “Next”.

cluster-1The next window will prompt you for the names of the hosts which you want to add to the cluster.  Below are my two example hosts drdb1 and drbd2.  After you’ve selected the hosts, press “Next”.


In the next window you will select which Cluster Communication stack to use with the cluster.  In my case, Heartbeat was installed so that was automatically selected.  If you’ve installed more than one, you should be able to choose either (I haven’t tested this setup however).

cluster-3The next window is a bit more complicated.  It’s where you setup the default /etc/ha.d/ file.  In my case I already had an existing file, so I was prompted to either keep it or to overwrite it.  In a blank new install, you’d be shown a default setup and you’ll have to add the appropriate nics to your setup.  I’ve been able to setup this up with only a single nic, but in a real setup, there would be more than one nic and one would be used solely for Heartbeat.  I’ll update this part of the setup further with more info in the future.  Right now, just select one nic which you will use for Heartbeat and I’d suggest using mcast and leave the ip and port numbers as default.cluster-4

The next window will display information if DRBD and Heartbeat (or Corosync) is loaded and running.  LCMC is designed to use DRBD and a service which uses it as it’s data store.  Even if you choose not to utilize DRBD in your setup, I’d still recommend installing it so LCMC doesn’t throw any error at you.  I realize it uses some CPU resources, but should be a bit deal if you’re not managing a data folder.

cluster-5You should now see a windows with a “Save” checked off and now you’re done.  Press “Finish” to complete the Cluster and LCMC setup.



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