Thanks to two concepts driving the data center today—economy and green computing—server virtualization is a hot topic in the IT world and a lot of hardware and software vendors are offering solutions. Virtualization solutions can have several benefits: they can let you easily migrate a virtual machine from one server to another, and let you provision a virtual as a reproducible clone image for, say,software development and testing.
The process for achieving virtualized server consolidation depends on your starting point:
- If you are designing your system from scratch, you will likely implement virtualization from the ground up.
- If your system already exists in the physical state, you will probably want to migrate from the physical environment to the virtual one.
I refer to the second process as physical-to-virtual migration, or P2V, and it's the subject of this article. Several methods, manual and automatic, are generally available to facilitate P2V migration. I'll talk about those methods and show you how to convert a physical server to a virtual machine using Clonezilla Live, a cloning-based solution.
With Clonezilla Live, you first create a system image from the physical server, then use the boot CD to restore the image onto the virtual machine's hard disk. It's simple and fast, and it should be useful for software developers, system administrators, and support engineers who want to analyze a system copy while maintaining the original one unchanged (and avoid possible hardware mismatch challenges).
Note: Virtual and physical systems hardware and software span a broad range, so the procedures in this article are meant as a reference guide. You may have to do some things differently to get them to work for your migration project.
Introducing Clonezilla Live
Clonezilla is an open source (GPL) Norton Ghost-like duplication and clone solution that you can use to clone a particular partition or entire disk. There are two releases: Clonezilla SE (server edition) and Clonezilla Live. Clonezilla SE is best suited for backup and restoring multiple servers simultaneously across the network. Clonezilla Live is a more lightweight build for single-machine cloning.
Clonezilla Live is a combination of Debian Live and Clonezilla; it has the following features and benefits:
- It clones only the used blocks on the hard disk.
- It provides multiple file system and even LVM support, including ext2, ext3, xfs, jfs, and LVM2 under GNU/Linux; FAT, NTFS under Microsoft Windows; and HFS+ under Mac OS.
- You don't need a diskless remote boot server (Diskless Remote Boot in Linux, DRBL) in Linux to set it up, as you do with Clonezilla SE.
- CD/DVD, USB flash/hard drives, and PXE boots are supported.
- It has a customized capability for boot and recovery procedure.
Clonezilla Live uses such existing tools as Partition Image,
clone the partition or disk. For unlisted file systems, Clonezilla uses
dd to copy all used and unused blocks.
Virtualization and system migration tools
When migrating a physical server to a virtual machine, you may run into the same limitations as when migrating one physical sever to another. For example, you can not move a 64-bit system image to a 32-bit platform. You are also most likely to encounter Hardware Abstract Layer (HAL) issues when restoring a Windows image onto the virtual machine.
Many free and commercial tools can help with system migration between the physical and virtual worlds (PlateSpin PowerConvert, VMware Convert, Microsoft® Virtual Server Migration Tookit and the cloning software); these migration tools can also solve the potential problems brought by the hardware mismatch between the physical server and the virtual machine. One of their roles is to pass the necessary drivers to the operating system kernel and initialize the drivers properly during the system boot phase. Of course, most of these P2V tools are more than you need for single-machine migration.
VMware Server is a free proprietary platform that provides support for multiple guest operating system types (from Windows, Linux, Solaris, etc.) on both Linux and Windows hosts. As a full virtualization solution, the virtual machine monitors (VMMs) running on the hypervisor provide the virtual machines with all the available types of hardware resources, including the virtual BIOS, virtual memory, virtual SCSI controller, virtual network card, etc. Because the guest operating systems are fully separated from the underlying hardware, they can run unmodified.
Now let's look at P2V migration using Clonezilla Live to clone a Windows system image onto the virtual machine hosted by VMware Server.
Step 1. Cloning a system partition
First, boot the physical server from the Clonezilla Live CD.
Clonezilla provides several boot choices. For example, you can select the To RAM option to load Debian Live with Clonezilla into memory and leave the CD-ROM available for other uses. Select the default, and you will get the language and keyboard layout settings. Leave the default as is.
Next, choose whether to use a GUI-based backup and restore wizard or a Debian shell for advanced access and operation. Use the Start_Clonezilla option unless you are an experienced user. You'll see how to use the shell under Restoring the image onto the virtual machine.
Now, there are two options listed regarding the cloning types:
- device-device is for device-to-device direct cloning.
- device-image is for device-to-image backup.
Because you are converting a physical system to a virtual machine, the device-image type is the better choice.
Next, you have to select the image directory where the backup image writes to or restores from, as shown in Figure 1. The ssh-server, samba-server, and nfs-server options are useful when you have a network connected, and local disk free space or a backup image is not available. In our case, we will clone the system partition and save it onto another partition within the same hard disk. If you select the local_dev, you have the opportunity to choose the USB device as the Clonezilla image repository.
Figure 1. Image repository choice
Depending on the internal and external (USB) inserted disks, you are now asked to select the place that will be linked to the image repository, /home/partimag. An image actually is a directory under /home/partimag with all the image-related information and data files. In this example, the system partition /dev/sda1 will be saved as the image put onto /dev/sda5. Thus, sda5 is selected to be mounted as /home/partimag/ as shown in Figure 2.
Figure 2. Image partition
Figure 2 also shows additional command information to mount the image device and the current file system layout with the free space usage report on /home/partimag. Make sure that the image repository has enough free space to store the data within the system partition.
As shown in Figure 3, you can confirm the home directory for the Clonezilla image within the image device.
Figure 3. Clonezilla mode
After this step, choose the mode that you are planning to use in Clonezilla Live. You can choose to save or restore the whole local disk or an individual partition. Select the third item, saveparts, for the partition backup.
After selecting the mode, you are asked to enter the image name
(Sys01-2009-02-23-img) and the source device (/dev/sda1) to back up. The
next several figures show advanced options for the image-creation process.
Because Clonezilla supports various file system formats and is integrated
with partition cloning tools such as ntfsclone, partclone, partimage, and dd,
the priority order of the tools to use can be set for the current file
system. Leave the default settings if you are not familiar with the file
system to be cloned. The default setting of
-q (ntfsclone > partimage > dd)
is best suited to our NTFS-based backup.
Figure 4 shows other parameters that you can set to optimize cloning.
Figure 4. Clonezilla advanced extra parameters: clone
For a Windows system image, the option
backup and restore time by excluding the swap and hibernation files. The
are recommended if you want to transfer the saved image to another place
and need to check image integrity when you restore the image.
Clonezilla Live also allows you to choose the compression method with efficiency and duration considerations. Some file systems do not support files larger than 2GB, so there is an option to set the maximum file size by splitting the image into multiple volume files.
Finally, you can designate an action with the
-p parameter to indicate what to do after the
cloning process finishes.
With your settings chosen, it's now time to review the operation and
confirm your choices. The backup and restore processes both use the
ocs-sr tool; after completing the settings through the Clonezilla GUI
wizard, the tool shows you the
command with the necessary parameters for achieving the same result
from the command line. It also creates a temporary file containing the
command, saved under the /tmp directory.
Now, sit back and wait for the backup to be completed. After it's done and the server boots up, transfer the image directory from the physical server to the place you will use as the restoration source for the virtual machine.
Step 2. Preparing the virtual machine
From here on, we'll be creating a virtual machine within VMware Server as the destination for system migration. Make sure that the host environment complies with the VMware Server and guest operating system requirements and limitations. Because the virtual machine will use the same processor as the host as a baseline, it requires that the host environment and the cloned physical server have compatible types of processors.
First, use the VMware New Virtual Machine Wizard to create the virtual machine. During the process, select the operating system version that matches the cloned one from the physical server. Also, you have to create a virtual disk equal to or larger in size than the partition where the original cloned system resides; Clonezilla does not support restoring an image from a larger hard disk or partition to a smaller one. During the Clonezilla Live restoration process, however, you are able to restore the image to a large hard disk according to the original disk layout.
Figure 5. Specifying the virtual machine's disk capacity
Note: The Clonezilla Live kernel might not support the SCSI disk for earlier VMware Server versions. In this case, when you create the virtual machine, use the IDE type for the virtual disks.
Second, change the virtual CD-ROM device to use the Clonezilla Live ISO image for the virtual machine, as shown in Figure 6.
Figure 6. Using Clonezilla Live ISO image in VM
Third, put the system image files from the previous section under the host server's second disk, Partition 0 of PhysicalDrive 1. Because VMware Server supports pass-through SCSI drive access on the host system, add another hard disk for the virtual machine with Partition 0 of PhysicalDrive 1 directly attached in VMware. At the restore phase, this device will be presented to /home/partimag.
Figure 7. Attaching the partition with system image
Now that you have a compact virtual machine created, it's time to boot the virtual machine from Clonezilla Live.
Step 3. Restoring the image onto the virtual machine
After the virtual machine boots up from the Clonezilla Live image, Clonezilla Live has the same GUI-based wizard interface for restoration as for backup until you choose the mode, as shown in Figure 8. In this example, we will enter the Debian-based Clonezilla Live shell directly to select a manual restoration.
Figure 8. Clonezilla Live shell
To restore the image under the Clonezilla Live shell, you must log on as root, as in Listing 1; this gives you full access to Clonezilla.
Listing 1. Becoming root user
user@debian:~$ sudo su - debian:~#
Now you need to determine the destination disk for restoration and the disk where the source image is to be placed. Listing 2 shows two local hard disks.
Listing 2. Viewing disk information
debian:~# fdisk -l Disk /dev/sda: 42.9 GB, 42949672960 bytes 255 heads, 63 sectors/track, 5221 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x00000000 Disk /dev/sda doesn't contain a valid partition table Disk /dev/sdb: 160.0 GB, 160039272960 bytes 255 heads, 63 sectors/track, 19457 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0xa0bea0be Device Boot Start End Blocks Id System /dev/sdb1 1 19457 156288321 7 HPFS/NTFS
/dev/sda is the virtual disk we created as the restoration destination; it is unformatted. /dev/sdb is PhysicalDrive 1 of the host server that we attached to the virtual machine directly in the form of a pass-through SCSI device; we have the cloned system image on it.
To restore the cloned partition image, the destination virtual disk has to
be presented to Clonezilla as formatted. You can use the
fdisk tool to write the label onto the virtual
disk. This procedure is shown in Listing 3.
Listing 3. Formatting the destination disk
# fdisk /dev/sda Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel Building a new DOS disklabel with disk identifier 0xee2955bc. 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 5221. 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) Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite) Command (m for help): Command action e extended p primary partition (1-4) p Partition number (1-4): 1 First cylinder (1-5221, default 1): Using default value 1 Last cylinder or +size or +sizeM or +sizeK (1-5221, default 5221): Using default value 5221 Command (m for help): Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. [ 866.679048] sd 0:0:0:0: [sda] 83886080 512-byte hardware sectors (42950 MB) [ 866.682658] sd 0:0:0:0: [sda] Write Protect is off [ 866.683795] sd 0:0:0:0: [sda] Cache data unavailable [ 866.683822] sd 0:0:0:0: [sda] Assuming drive cache: write through [ 866.686443] sda: sda1 [ 866.695530] sd 0:0:0:0: [sda] 83886080 512-byte hardware sectors (42950 MB) [ 866.698278] sd 0:0:0:0: [sda] Write Protect is off [ 866.699422] sd 0:0:0:0: [sda] Cache data unavailable [ 866.699495] sd 0:0:0:0: [sda] Assuming drive cache: write through [ 868.702058] sda: sda1 Syncing disks.
We can accept the default values in Listing 3. The partition type is not a concern at this time because it will be re-created by Clonezilla during the image restoration.
As with the backup procedure, you must mount a writable device or space as /home/partimag, then Clonezilla will search the cloned image directory under /home/partimag. To prepare the restoration from the image on the partition /dev/sdb1 to the newly created partition /dev/sda1, first mount /dev/sdb1 to /home/partimag with the writable privilege. Note that here, /dev/sdb1 is an NTFS file system on the host server, and it may be open, so a force option might be required to mount it successfully. See Listing 4.
Listing 4. Mounting the image device to /home/partimag
debian:~# mount -t ntfs-3g /dev/sdb1 /home/partimag -o force debian:~# ls /home/partimag Sys01-2009-02-23-img
When /home/partimag and the destination partition are ready, you have to choose the best way to restore the image for your environment. Just as for backup, Clonezilla provides a variety of advanced and flexible options for image restoration. See Figure 9 for the restoration parameters and their meanings.
Figure 9. Clonezilla advanced extra parameters: restore
For Windows system image restoration, the boot header has to be written to
the destination disk. To achieve this, use
dd to create partition table) and
restores the prebuilt MBR from syslinux). The
hnX PC (
X is 0 or 1)
option is good for ensuring that your environment has a
machine name. In case you don't want to keep your current destination
partition layout, you also can try
another partition-relation parameter to create another partition table.
Listing 5 restores the image Sys01-2009-02-23-img from /home/partimag (/dev/sdb1) to the destination device, /dev/sda1.
Listing 5. Using the command line to restore the image
debian:~# /opt/drbl/sbin/ocs-sr -e1 auto -c -t1 -r -j3 -cm -j0 -p reboot restoreparts "Sys01-2009-02-23-img" "sda1"
Figure 10 shows the summary and progress updates you'll receive after you confirm the choice. After that, you have your cloned system on a virtual machine.
Figure 10. Clonezilla restore summary and progress
When the restoration is done, you can watch your system boot up from the virtual machine. To get better performance, install the VMware Tools for the virtual operating system.
This article has shown you how to complete a physical-to-virtual system migration using an image-based method and open source tools. Remember to use the steps here as a reference; due to differences in environments, your system and migration experience may be different from what you read here.
- The Clonezilla site provides full and detailed information and resources on Clonezilla Live.
- "Manage partitions and disks with GParted-Clonezilla live CD" (Linux.com, July 2007) provides a guided tour of Clonezilla.
- The DRBL FAQ/Q&A can answer many questions you might have about Clonezilla Live.
- VMware provides data and documentation on its virtualization technologies, including the VMware Server.
- Knowledge of HAL is needed if you're migrating a Windows system.
- "How Convert Physical to Virtual" (VMTS) shares valuable experience on P2V migration via cloning.
- Linux has a long history of
virtualization efforts, many of them documented at developerWorks; for
- "Virtual Linux" (December 2006) gives an overview of virtualization methods, architectures, and implementations.
- "Discover the Linux Kernel Virtual Machine" (April 2007) describes the first virtualization solution to be part of the mainline Linux kernel.
- "LXC: Linux container tools" (February 2009) shows how to provide lightweight virtualization without encountering the complexities of full virtualization.
- In the developerWorks Linux zone, find more resources for Linux developers, and scan our most popular articles and tutorials.
- See all Linux tips and Linux tutorials on developerWorks.
- Stay current with developerWorks technical events and Webcasts.
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