October 4, 2007 by Arun PC
Note:- This article is technical.May not be useful for people NOT working with virtual machines
Scenario
The Host machine runs Vmware Server on Linux and the guest also runs Linux virtual machine.
Problem Summary
When trying to ssh from the Host Linux box into the guest Linux box, it just stays with the command and fails to execute or throw an error.It just remains like this.
ssh user@192.168.X.Y
<nothing happens after this.No error thrown>
The logs(/var/log/ssh or /var/log/auth.log) also doesnt show anything useful.
Test
Host machine can ssh into other machines in the network.
Host machine cannot ssh into any Vms it carries.
Host machine can PING to all Vms aswell as the other machines on the network.
Diagnosis
The problem is with the ethernet card settings. We need to tune the ethernet card settings with a tool called ethtool.(see MAN ethtool pages for various options).
By executing the below given command we disable some kernel modules like Rx checksum and scatter gather which solves the problem.
ethtool -K eth0 sg off rx off tx off tso off
Hope some of you found it useful.
Thanks,
Arun.PC
Posted in Technical | 7 Comments »
October 1, 2007 by Arun PC
What is VDI?
VDI is Virtual Desktop Infrastructure.
In order to understand VDI, you need to understand what ‘virtual desktops’ are. Virtual Desktops are not real desktops but who cares? You don’t need to if you are an end user.
What i mean by that is, you interact with your virtual desktops just like the way you interact with real desktops. Nothing changes. Nothing.
Let us take an example.Assume that you are using your Windows XP/Vista desktop with all your favorite applications like Yahoo messenger, Photoshop, MS excel, PowerPoint etc….You also have picture of your dog as the wallpaper. This is the desktop you use at home.You love your desktop and you are so familiar and accustomed to it. You don’t want to change it because it works for you and it is very personal.
Imagine this desktop is accessible to you everywhere. ie..an omnipresent desktop. You can access your applications and data from a friend’s place, local bar, your in-law’s house, office or a different country altogether.This is possible through virtualization and virtual desktop infrastructure. Ubiquity of access is just one of the feature of VDI. There are numerous others like security, cost, backup etc..
From an end user’s perspective, nothing changes in terms of his interaction with his desktop. He just needs to login to the network and his desktop is click away. His desktop gets streamed to him wherever he is and whenever he needs it.He can always save the changes he make; his preferences of applications, and all the other desktop settings remain intact.The difference lies in the system administrator’s job.Desktops are no more deployed.They are hosted and delivered.The user has an individual virtual desktop on the server elsewhere and they are allotted to him as and when they are needed. These desktops are streamed over the network and user gets his desktop irrespective of his physical location.
The obvious constraint to this technology is that desktops always need to be connected to the network.With the increasing adoption of broadband and companies working on caching and offline technologies, this issue sure to be mitigated to a large extent.
If you find the whole idea confusing, foggy and abstract, don’t worry; you are not alone. This is a whole new technological shift.This trend is not an evolutionary or an incremental change in application and desktop computing but it is a radical shift.
I am also eagerly waiting to see the how the story will unfold and in the coming days, i will keep you posted on the intricacies and developments in this area.
See you.
Thanks,
Arun.PC
Posted in VDI, virtualization | 2 Comments »
