When you are deploying clusters on real hardware - again and again - to test the deployment - it is quite helpful to have the hardware in a clean state. Unfortunately there is no real "Factory reset" button on hard drives.

However, there is an simple solution to this problem: When you install your cluster using PXE boot (like when using Crowbar), you can easily wipe all the hard drives of the whole cluster using this config.

A word of warning at this point: The following steps describe how to DELETE data from your whole data centre (if you are not careful). So do backups, use with care, etc. You have been warned.

Step 1: Getting DBAN

DBAN is a small custom linux boot image that has only one purpose: Delete all disks.

Download the ISO and extract the DBAN.BZI file.

Step 2: Set up PXE boot

We are using this setup out of our Crowbar installation, so the PXE environment is already setup. If you use it stand alone, with Cobbler or something else, adjust the paths accordingly.

In the Crowbar case, create a file /tftpboot/discovery/pxelinux.cfg/nuke with the following content:

DEFAULT nuke
PROMPT 0
TIMEOUT 10
LABEL nuke
  KERNEL DBAN.BZI
  append nuke="dwipe --autonuke --method zero" silent vga=785
  IPAPPEND 2

Copy the DBAN.BZI file to /tftpboot/discovery/

Step 3: Prepare the nuke

Since we are going to nuke anything anyway and do not want chef to interfere with our evil plans, we stop chef-client on the admin node:

bluepill chef-client stop

Now we enable the self destruct button:

cd /tftpboot/discovery/pxelinux.cfg/
ln -fs nuke default

Step 4: Nuke the cluster

To nuke the entire cluster (excluding the admin), just delete all nodes from crowbar - either by clicking through the UI or by using the crowbar CLI tool.

Then reboot the nodes via IPMI and wait for the data destruction to commence.

Nuking the admin node can be done using the DBAN iso via some virtual IPMI drive.

Summary

You can easily reset a lot of machines using PXE boot and DBAN. When you are using Crowbar the setup shown here makes it easy to start completely fresh any time.

Crowbar "cleans" the hard disks itself when you trigger an install, but some times this does not suffice. Some LVM parts remain intact and the following installation does not work properly. Using the DBAN nuke we can ensure that we really do start with empty hard drives on every node.

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