What is OVF (Open Virtualization Format)

Hi , Back to coding ūüôā¬† If you are Amateur Sys-Admin like me you cannot just rely on running scripts and playing with network. You would love to write your own peice of code for solving the problem in an efficient way and the way you want it to be.

Same happening to me now , while running PDC Cloud based on OpenNebula I have to write an OVF wrapper for clients.

But First

What is OVF?

With the rapid adoption of virtualization, there is a great need for a standard way to package and distribute virtual machines. VMware and other leaders in the virtualization field have created the Open Virtualization Format (OVF), a platform independent, efficient, extensible, and open packaging and distribution format for virtual machines.

The OVF format,  provides a complete specification of the virtual machine. This includes the full list of required virtual disks plus the required virtual hardware configuration, including CPU, memory, networking, and storage. An administrator can quickly provision this virtual machine into virtual infrastructure with little or no manual intervention. In addition, the OVF is a standards-based, portable format that allows the user to deploy this virtual machine in any hypervisor that supports OVF.

Read complete here:


This does not look like a tar

Hi , if you get the following message

ÔĽŅtar tzf ubuntu-10.04-amd64-base-1.1.img.gz

This does not look like a tar archivetar: Skipping to next headertar: Exiting with failure status due to previous errors

Try only

 gzip -d ubuntu-10.04-amd64-base-1.1.img.gz

Debian update failed and its solution

W: Failed to fetch  404 Not Found

W: Failed to fetch  404 Not Found

W: Failed to fetch  404 Not Found

E: Some index files failed to download, they have been ignored, or old ones used instead.


open /etc/apt/sources.list and change security deb into

deb lenny/updates main contrib non-free


Map network drive, connect as different user to same Server

I ran into an interesting problem today. I was helping someone configure Samba and had shown him the XP/2000 trick of mapping a network drive and having it connect as a different user. He then wanted to map another network drive to another share on the same server, but this time connect as an entirely different user.

Windows won’t do that. You can’t use different credentials to connect to different shares on the same server. Once you provide a username and password for an smb server, Windows XP/2K wants to use that for ALL shares on that server.

That’s actually a useful feature. For example, I use that to connect printers that otherwise would need authentication. By mapping a share that reconnects at logon, the printers are automatically available because attempting to connect to them will automatically use the same logon/password as the mapped drive did.

But darn it, this person really needed to connect multiple times with different user ids. After some digging, we figured out how to do it: fool Windows into thinking it isn’t the same server. One way to do that is to use the ip address for one connection and the smb name for the other, but that only gives you two connections. To get more, you need to add aliases into DNS and configure Samba with the same netbios aliases. With that trick, Windows happily makes multiple connections with different user name/password logons. Basically, it doesn’t realize that it is connecting to the same machine.

See for an explanation of how Windows decides what credentials to use.


adding new disk in Linux , Partition it and Formating

after physically adding check if your disk is added in /dev

fdisk -l

Disk /dev/sda: 36.4 GB, 36420075008 bytes

Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      104391   83  Linux
/dev/sda2              14        4427    35455455   8e  Linux LVM

Disk /dev/sdb: 36.4 GB, 36420075008 bytes

My new disk is /dev/sdb

making partition as

fdisk /dev/sdb
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel. Changes will remain in memory only,
until you decide to write them. After that, of course, the previous
content won't be recoverable.

The number of cylinders for this disk is set to 4865.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
   (e.g., DOS FDISK, OS/2 FDISK)

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
Partition number (1-4): 1
First cylinder (1-4865, default 1): 1
Last cylinder or +size or +sizeM or +sizeK (1-4865, default 4865): 4865

Command (m for help): t
Partition number (1-4): 1
Hex code (type L to list codes): 83

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

Now Format it :

mkfs.ext3 -b 4096 /dev/sdb1

Add in /etc/fstab

/dev/sdb1               /srv                     ext3    defaults        1 1


mount /srv



Installing gcc on Xubuntu

gcc is not installed on Xubuntu by default and you cannot build packages from source.. do this to install and other build packages.

zss@peace-maker:/etc/apt# sudo apt-get install build-essential


Online Resources for Windows HPC Server

Online resources for this release of Windows HPC Server 2008 are available online:

  • Windows HPC Server 2008 Technical Library (
  • Windows HPC Server 2008 Command Reference (
  • Windows HPC Server 2008 PowerShell Reference (
  • HPC Server Basic Profile Web Service Operations Guide (
  • Configuring Failover Clustering in Windows HPC Server 2008 Step-by-Step Guide (
  • HPC Cluster Manager Help (

Filesharing on MSHPC


If you are running MSHPC (Microsoft HPC Cluster) and want to share folder with your users, you end up using SMB , Right ?  But This is not secure and have several vulnerabilities as mentioned here .

So what is the solution , For example in my case i have the issue to share folder with Matlab users .

Keep asking to Matlab and Microsoft team , the solutions got so far are

1) Use AFS

2) Use VPN .

I will try to use VPN now and will share my experience.

Some trail of my search so far on this issue:


SMB Sharing on Internet for MSHPC and Matlab

When Integrate Matlab parallel computing toolbox with HPC Schedular configuration , it needs a property “DataLocation” which has to be a shared folder between client desktop running Matlab and MSHPC schedular and compute nodes.

In windows sharing between Headnode and compute nodes is enabled with SMB Sharing and as this sharing is on Application network or on Private Netwok , the security concern is not so much , but in the case of Matlab this raise an issue . i.e.. Usually if you run SMB either on TCP or on Netbios for bothe ports 135 and port 445 is blocked by major ISPs.

The reason for this block as ISPs mentioned is “security concern”.

Solution: I have been in contact with Matlab support and they recommend us to Use VPN.  But it is again increase the complexity from Users side.