Thursday, December 15, 2011

XenServer - Cannot Shut VM

Have you ever experienced  a situation where you could not shut one of your running XenServer running VM's?   In this brief article I'll present a workaround for this common problem...  From my personal experiences this problem is often caused when the domain of the specific VM is still active (this often happens as a result of inproper shutdown and/or storage cutoffs) - in such case the domain needs to be destroyed manually.  OK, so here's the problem - from the XenServer (v 5.6 SP1) dom0 CLI I'm trying to shut a VM (using the force option): #xe vm-reset-powerstate vm=xxxxxxx force=true
However the output I get is:  The operation could not be performed because a domain still exists for the specified VM.
vm: f087dxxxxx (xxxxxx)
domid: 5
  From the output we will need  two parameters :the domain id (5 in our case) and the UUID of the problematic VM , so write them down somewhere. Now we need to destroy the currently active domain, XenServer includes couple of good tools under /opt/xensource, the command that is relevant is:   #/opt/xensource/debug/destroy_domain -domid 5  Now, finally, we will be able shut the VM with:  #xe vm-reboot uuid=XXXX --force  And we're done.  Hope that helped some one out there. Cheers!

Wednesday, December 7, 2011

Perl SSH Log-in

Hi Folks, 

In the following post I will demonstrate a password-less login into Cisco appliance via the SSH protocol using a Perl script.

When combined with cron, it can be a great solution for saving your appliance configuration (show run) or checking status without the need to log-in into the appliance each time.

Pre requirements:
  • Perl
  • SSH client (duh!)
  • Net-SSH-Perl module

On Red-Hat (and friends) the module can be obtained via:
#yum install perl-Net-SSH-Perl -y 

Be sure to have a proper repository installed such as rpmforge 
Our simple script connects to the Cisco appliance via SSH and runs "show run" command (this account has enabled privilege).
The script itself should look like this:

#!/usr/bin/perl -w
use strict;
use warnings;
use Net::SSH::Perl;
my $ssh = Net::SSH::Perl->new('hostname');
$ssh->login('username', 'password');
my($out) = $ssh->cmd("show run");
print $out;

Since the script contains your appliance username & password don't forget to remove permissions for others:
#chmod o-rwx

Now, let's run the script:

Building configuration...

Current configuration : 8011 bytes
...more output ommited...

Works like charm!
Now, the only thing is left is to synchronize it with cron :)