Shared Nothing Diskless Boot

It is possible to run a computer with no persistent storage for its root file system other than a single image downloaded an held in RAM. The computer does not needs a local disk. The computer also does not need a SAN or NAS device for the Root File system.

There are numerous uses for this style of booting.  A short list:

  • Debugging the installation processes of software packages
  • Running computationally intensive tasks on a large array of nodes
  • Inventorying the hardware on new servers
  • Deploying a light management framework for virtualization hypervisors

Here is a brief overview of the pieces needed to set this up for testing purposes on a workstation running KVM.

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Finding Java Classes

I’m back on a Java project. Been a while, and I want to capture some of the tricks I’m using.

Right now, I’m just trying to import the project into eclipse.  Seems that the current team members don’t use it.  I’m an IDE kind of guy, at least when it comes to Java.

Building the .classpath file can be tricky.  However, since I know that I have a good build, and that this project it a good participant in the Fedora build process, I have the advantage of knowing that my packages reside in /usr/share/java.  Still, all eclipse gives me is a set of classes that it can’t find.  how to find them?

This project uses CMake.  I could look for all of the Jar files in the CMakeLists.txt files, and I might do that in the future.  However, a trick I’ve developed in the past has come in handy.


echo $1 | sed 's!\.!\/!g'


for JAR in `find /usr/share/java -name \*.jar -type f ` 
	do for CLASS in `jar -tf $JAR |  grep \.class` 
		do echo $JAR $CLASS  
done > /tmp/alljars.txt


First, the make_alljars function creates a map in (value key) order. The value is the Jar file name, and the key is the class name. To fine a Jar file that contains a given class (in this example netscape.ldap.LDAPConnection) , run:


grep `class2path  netscape.ldap.LDAPConnection` /tmp/alljars.txt

And the output is

/usr/share/java/ldapjdk.jar netscape/ldap/LDAPConnection$ResponseControls.class
/usr/share/java/ldapjdk.jar netscape/ldap/LDAPConnection.class

This works really well with eclipse, in that the error messages have the name of the class. You can then just highlight the class name, paste it into the command line in place of the class I have above, and when you get the Jar file name, you can highlight to save to the clipboard. From The right click context menu pick Java Build Path and then Add External Archive and then paste the whole path in.

IPAddress for local Virtual Machines

When running Fedora as a KVM/Qemu  host for  virtual machines, you have the issue that you don’t know the IP Address for a virtual machine once you create it.  IP addresses that are assigned via

The MAC Address is in the config file saved in


Once you start the virtual machine, you can fetch the IP Address from the DHCP lease file in:


To correlate the two:




MAC=`cat /etc/libvirt/qemu/$VMNAME.xml |   xml2 | awk 'BEGIN{FS="="} /mac..address/ {print $2}'`

IP=`grep $MAC /var/lib/dnsmasq/dnsmasq.leases | cut -d' ' -f3`

#$VMNAME has MAC $MAC and IPAddress $IP
echo $IP


This must be called as root or via sudo.


Chris Lalancette notes that the cannonical version of the MAC address can be found using

virsh -c qemu:///system dumpxml $VMNAME

Removing empy comment blocks

Eclipse can automate a lot of stuff for you. One thig is did for me was automating the serialVersionId generation for all the serializable classes in my tree.
They look like this:

     private static final long serialVersionUID = -9031744976450947933L;

However, it put an empty block comment in on top of them, something I didn’t notice until I had mixed in this commit with another. So, I want to remove those empty comment blocks.


for JAVAFILE in `find . -name \*.java`
     sed -n '1h;1!H;${;g;s! */\*\*\n *\* *\n *\*/ *\n!!g;p;}' \
         < $JAVAFILE > $
     mv $ $JAVAFILE

Thanks to this article for how to do the multiline search and replace.

Snapshot VMs

This past week at the  Red Hat summit I got the chance to demonstrate Enterprise IPA, the Red Hat version of FreeIPA, at the Red Hat booth.  One of the aspects of IPA we want to showcase is registering client systems.  That means that I wanted to be able to get a client system in the pre-installed state pretty very quickly.  My approach was to use Qemu/KVM virtual machines.  I had one VM image that I did not touch, and all the rest of the virtual machines will be snapshots that overlay that image.

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