June 2009 Archives

Maybe you have followed my guide to easy virtualisation with Sun's VirtualBox software and you are familiar with the basics of running a virtual machine inside your normal Windows or Linux system by now. I hope that you enjoy the many features of your new virtual machine as most devices used by the virtual machine just work out of the box. Reading CDs and using the audio device for playback should work right away and setting up a printer via the network connection is a matter of few clicks.

But the one problem you have certainly run into by now is the low display resolution which defaults to 800x600 pixels, considerably impeding your freedom on the screen. Two simple steps will sort out this problem forever. First select a suitable "Monitor Type" in the Administration - Display dialog and save the setting. Then edit the file "/etc/X11/xorg.conf" and add something like the following in the SubSection "Display" part:


After logging out and restarting the X server again you should have a much bigger screen that almost covers the whole display if you switch into FULLSCREEN mod with <Ctl>F.

Guest Extensions pave the way for a seamless desktop experience

During the installation of VirtualBox a custom kernel module was being built that enables the host system to manage the guest, but the guest system runs without any consciousness of the fact that it is only a virtual machine. To ensure a better integration between the host and the guest, SUN have developed a package called "Guest Extensions" that must be installed inside the guest to make it VBox-aware. The installation of Guest Extensions culminate in compiling another kernel module that is being used by the guest to improve communications with the host and to make additional features like shared folders available.

Before we can use these desired features we still have to prepare the guest system to compile kernel modules, that means we have to install a full development stack inside the guest system for kernel modules first, and then install the Guest Extensions. Use the following yum command to prepare the CentOS/Fedora host:
 

The Guest Extensions come as an iso-file "VBoxGuestAdditions.iso" that could be found in the directory "/usr/share/virtualbox". Make sure that this iso file is available as a CD-iso-image to the guest system by adding it to the appropriate section in the Virtual Media Manager menu. Restart your virtual machine to make sure the new, updated kernel is actually running and start the setup script "VBox LinuxAdditions-x86.run" on the CD image after you have mounted the iso-file from within the guest system. After rebooting the virtual machine the new kernel module for the guest becomes active and the extensions are ready to use. The first thing you'll notice ist that the mouse pointer is no longer confined to the guest window, you can click on everything that is visible on the screen, no matter if it is a host or a guest window. And, of course, you now can copy and paste text between the host and the guest as you like it. A much more important change took place behind the curtain, your access to the hard disk is faster now. Let's have a look at the following table which gives an overview over transfer rates measured on my laptop.

Action	CentOS 5.2 HOST	Fedora 10 GUEST WITH Guest Extensions	Fedora 10 GUEST without Guest Extensions
creating files with zeroes	27.1 MByte/sec	21.8 MByte/sec	14.1 MByte/sec
copying files	12.47 MByte/sec	11.96 MByte/sec	N/A
writing to network shares	12.26 MByte/sec	5.6 MByte/sec	5.4 MByte/sec
writing to shared folders	18.0 MByte/sec	6.7 MByte/sec	not available

As you can see the performance has considerably improved for writing files to disk and is almost the same for writing normal files while there is still a huge difference when network attached storage is used to extend the usually poor disk space of the virtual machine. But the use of virtual folders at least enables the host system to write data to the guest's file system rather quickly, while the guest does not really gain any speed doing the reverse operation.

Anyway, installing SUN's Guest Extension truly polishes your virtual guest machine and lets it shine brighter than before.

I know, you are one of those people who know that it is absolutely essential to make regular backups of your system's hard disk. There is no excuse not to make regular backups, but as we all know, we don't really do that. Or is it just me?

No, you have to admit that even though the reasons to make backups are indisputable, something strange always - no, not always, but many times - keeps you from doing the necessary, updating your backups and securely storing them away. Making backups is not fun, but that's not the reason why we don't do it regularly. I suspect that you as well as I simply don't have the right tool yet, to initiate an automatic process that boils down to getting a reliable backup complete and safe to restore, which does not require much attention while assembling the data for us.

Fortunately this situation is going to change dramatically for you, today. I've run into a backup solution that is just that, an automatic process that does not require user intervention when started to do the right thing. It's called CLONECILLA and is essentially a Live Linux system, optimised for backup and recovery.

Clonezilla - Your bootable backup CD

Clonezilla can be downloaded here as an ISO-file of 106 megabytes.. This file contains everything that makes up a bootable Linux system, so be careful to write this downloaded iso-file to your CD in raw-mode. Because it's of no use to have the iso-file on a CD in another file system, the iso-file is the file system and it is the only thing that has to be on the CD.

Did I mention that Clonezilla is a backup solution that covers all sorts of partition types, so that our windows-using friends could use it, too? Clonezilla has the ability to clone a complete hard disk no matter what kind of partition your disk comprises of. It even backs up the master boot record and the partition table, you will get a complete set of data from which all or any part will be recoverable when you need it. And all data is created as zipped files of max. 2 gigabytes size so that everything can be burned to DVDs, if needed.

Setting Clonezilla on the right track

As we are now heading for a complete backup of your laptop's hard disk, one thing is to be considered before we start, where will all the backup data be stored? Fortunately Clonezilla offers a number of possible storage media ranging from an additional (plugable) local disk, a SSH server or a SAMBA server to the traditional NFS server. I assume that you have a portable USB hard disk on which you will store the backup. Please ensure that the free space on this disk is about half of the size of what you are going to backup, and add a little bit of a buffer, too.

I have found that a second thing is important before you start letting Clonezilla create the backup, make sure that all partitions of your hard disk can be mounted. Best practice would be to perform a file system check on all partitions before starting the Clonezilla boot CD.

The following few steps are all you need to initiate a full backup of your laptop's hard disk and you will see that once you've selected a few things the rest is going in a jiffy.

Step 1	Boot your Clonezilla backup CD, select language and keymap, then select "Start Clonezilla"
Step 2	After selecting the backup media (local_dev) power on your USB disk and allow a few seconds for the system to recognize your new hard disk on which the backup will be stored. Clonezilla creates a directory on the USB disk derived from the date and time of the backup. You can choose where to store this directory on the disk. You can always switch to another terminal using <CTR><ALT>F2 to see that the USB disk is now mounted on /home/partimag. All files go into this directory.
Step 3	Select "savedisk" to ensure that the whole hard disk is backed up. When the partition information is read in Clonezilla will start the backup process automatically.
Step 4	Depending on the size of your hard disk, you can now relax and let Clonezilla compose your backup for you. Check the backup directory in the meantime to see it filling up with data.

The performance of creating the backup is very good, it took 47 minutes for a 30 gigabyte data partition on my three year old laptop. The whole disk (120 gigabyte) was ready after two and a half hours time leaving me a total of 66 gigabytes of compressed data.

Try Clonezilla today, it takes very little time to be secure. No excuses!