The one and only enterprise grade virtualization software available in Open Source world is Xen. It's highly secure, reliable and works with minimum hardware overhead. The reason why it has minimum overhead lies with para-virtualization, in which the virtualization layer doesn't create a full-fledged virtual machine. Instead, it forks out the host OS to create virtual instances of the host OS itself. But with all the positives, there is also a huge drawback-the configuration and installation of the same is a nightmare.
Traditionally, everything is done through command line interface and by modifying the text based configuration files. So, if you are not a Linux geek, this is obviously not your cup of tea. Still an important point to note is that with the release of this latest offering of Fedora Core 6, things have become a lot easier. Now you can use a graphical tool to install and use virtualized Linux instances very easily. Let's see how you can do it.
Step 1: Installing Xen
To install Xen and all required components, including the graphical configuration interface, all you have to do is to select 'Virtualization' in the 'Base' package group, while doing a customized package selection during FC6 installation.
After the installation is over, while booting, you will see two kernel instances in the Grub menu. Next, to make Xen active and usable you have to select the kernel entry that ends with 'Xen'. The system will boot up normally, but with Xen support.
Step 2: Pre-requisites
After the system is installed, you have to configure a few things to make sure that XEN works perfectly fine. First of all you have to create a share, which can be either HTTP, FTP or NFS and then copy the full FC6 installation repository into it. This is required because the graphical installer for XEN can only read installation data from these three media. We tried creating an HTTP site with FC6 installation repository using Apache but some unknown problem occurred and we were not able to connect our guest OS with the site, so we decided to go for an NFS-based installation.
You can create an NFS share on any machine, which is in the same network of the host machine. It can even be the host machine itself. To create an NFS share, you have to first open the file called /etc/exports. You can do it by running the '#vi /etc/exports' command.
Now write the following line in the file, save and exit.
/FCTree (rw)
Here FCTree is the folder where you have copied the installation files of FC6. Now start/ restart NFS server by running the following.
#service nfs restart
Now your NFS share is ready to work.
Step 3: Installing the Guest OS
After the system boots up, go to the Application menu, select Programming submenu and click on Virtualization. This will open up a graphical window. The first screen is only a Help screen, so just press Forward to proceed. The next screen will ask you for the name of the VM instance. Give a relevant name and proceed.
In the third screen you have to fill in the UNC (Universal Naming Convention) and share name of the NFS share you have just created. The string will look something like “Nfs:<ip-address-of-the-nfs-server>:/<share-name”. For example, in our case it was 'Nfs:192.168.5.56:/FCTree'. And after you have given the path properly, just hit the Forward button once.
Step 4: Allocating hard disk
On the next screen, you have to select either a physical or a virtual (a blank file) hard disk. Since our test machine had only one disk, we decided to create a virtual hard disk. For this, all you have to do is to first select the 'Simple File' radio button and then give a file name and file system location where you have all read and write rights. Just below the text box, you have to fill in the desired size of this virtual hard disk. After this is done, proceed to the next screen.
Step 5: Allocating CPU and RAM
On the screen that you see now, fill in the CPU and RAM for the GuestOS. For instance, if you have a machine with multiple processors or a multi-core processor, you can dedicate one to each of the VMs you install. In the RAM field, you have to specify the exact RAM capacity you want to allocate to the guest machines.
Step 6: Installing and saving the OS
At this point you are done with the entire configuration. The next screen of the wizard will just show you the summary of all the settings you have made and clicking on the Finish will start a new window where you can see the guest machine's installation process.
Just keep one thing in mind that while installing, if you press Shutdown button at the top of the window, the GuestOS will either stop or vanish. Also there is no way you can retrieve the changes you had made.
So if you want to exit or pause the GuestOS, you have to first go to the 'Virtual Machines' Menu and select Save. To restore the saved session, you have to click on the 'Restore Saved Session' in the same menu.
Source: PCQuest
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