Netscaler 10.x, XenServer 6.2 and Cloudstack

Quick tech note. After my Cloudstack testbed upgrade my Netscaler VMs no longer booted. The issue was similar to the one described in CTX135226 but affected both Netscaler 9.3 and 10.1 VMs.

After wasting a few good hours it turns out that this is caused by the presence of a DVD drive in the VM. The mere presence of a DVD drive, even if no ISO is loaded, somehow messes up with the Netscaler boot process under XenServer 6.2. The workaround is trivial:

  1. 1. Spot the DVD drive (hdd) using the vbd-list command

  2. # xe vbd-list vm-name-label=NetScaler\ Virtual\ Appliance
    uuid ( RO) : 5e218b95-68e9-37b2-860f-8b97678e2c02
    vm-uuid ( RO): ab229b8f-2b18-4931-b80b-30ab8265b843
    vm-name-label ( RO): NetScaler Virtual Appliance
    vdi-uuid ( RO): 5bcf6d76-1d2f-411a-9dd7-469aad0f86ae
    empty ( RO): false
    device ( RO): hdd

    uuid ( RO) : 9d6ff62c-93fa-3af5-b4b5-c5c66a0556e4
    vm-uuid ( RO): ab229b8f-2b18-4931-b80b-30ab8265b843
    vm-name-label ( RO): NetScaler Virtual Appliance
    vdi-uuid ( RO): 7b1fa1ff-7388-4e5a-8c67-00e4d943a470
    empty ( RO): false
    device ( RO): hda

  3. Destroy it

  4. # xe vbd-destroy uuid=5e218b95-68e9-37b2-860f-8b97678e2c02

  5. 3. Power on the Netscaler VM again; this time it should work like a charm

This is good enough if you have access to the XenServer running the VM. Not as good of a workaround for a Cloudstack environment which requires you to jump a few extra hoops. Specifically, if you are using XenServer you can update the StartAnswer method to selectively invoke the createVbd function in CitrixResourceBase.java: if the guest OS type evaluate the guest OS type matches “Other install media” and the disk type is ISO skip VBD creation. Here is the relevant sample code snippet:


public StartAnswer execute(StartCommand cmd) {
...
String guestOsTypeName = getGuestOsType(vmSpec.getOs(), vmSpec.getBootloader() == BootloaderType.CD);
for (DiskTO disk : vmSpec.getDisks()) {
if (type == Volume.Type.ISO && gguestOsTypeName.toLowerCase().contains("other install media")) {
s_logger.debug("mperedim: skipping VBD creation");
} else {
createVbd(conn, disk, vmName, vm, vmSpec.getBootloader());
}
}
...

One can improve this workaround by mapping Netscaler VPXs to a dedicated OS template, so that DVD drives are still created for other VMs that get mapped to the “Other install media” XS template.

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