How to boot a virtual machine image from the network

virtual-machines

I have many machines which require the same configurations. My goal is to boot them all from the network and load a virtual machine. It would be wonderful to have one image for all of our customer service machines. That way, I could load the virtual image, perform updates, and know the next time they boot up they will have all the changes. Ideally, the machines would store the image locally and only download a new image if there has been a change.

With all the information out there on "desktop virtualization", "PXE booting", and "virtual machines", I feel lost. I have been reading for hours and feel like I have only just scratched the surface.

I would like to do this using open source or free software. Any suggestions?

Best Answer

You are combining two things: (1) diskless booting which is common in HiPC clusters, where tools like compilers, libraries, etc, are stored on a clustered file system like Lustre or NFS; (2) virtual disk images (vmdk or vdi, or whatever else).

In case (1), you need a tftp server and a dhcp server, along with a modified initrd image for customized drivers, scripts, etc.

http://www.pixelchaos.net/2009/02/15/diskless-booting-with-pxe-and-nfs/

In case (2), given all machines are same, including configurations, you can nfs mount the virtual disk image. Write a script that checks for any changes like whether the existing image is same as nfs mounted; if they are not same, copy this image to boot partition and reboot it. You need to add this script in initrd. You can play with that.

http://www-conf.slac.stanford.edu/afsbestpractices/Slides/afsboot.pdf

The paper above gives you some clues. You better focus on how the whole boot process works, etc.

If you are using ESXi, there is a better way to achieve what you want: export nfs to esxi hosts. Keep the vmdk and -flat.vmdk files on the nfs server, and change vmdk location in .vmx file. During the next boot, it picks up your new image.

Related Solutions

Virtual Machines – Safe Range of MAC Addresses for Virtual Machines

There are actually 4 sets of Locally Administered Address Ranges that can be used on your network without fear of conflict, assuming no one else has assigned these on your network:

x2-xx-xx-xx-xx-xx
x6-xx-xx-xx-xx-xx
xA-xx-xx-xx-xx-xx
xE-xx-xx-xx-xx-xx

Replacing x with any hex value.

How to manage changes to set of cloned Virtual Machines

Snapshots: Preferred Approach

Create a base VM on your machine. For your purposes, you will be perfectly fine using a compact/thin-provisioned disk image file, so don't use a fixed-size one.
Shut down your instance of the base VM. (Suspend/hibernate is not sufficient.)
Take a snapshot.
Distribute it to the developers after you have taken the snapshot.
When the time comes, fire up the base VM and update it. Any changes that you make will be written to new "delta" files, which will only be as large as the accumulated changes made since you took the snapshot. Because you have taken a snapshot, that enormous disk image file will remain 100% unchanged.
Shut down your instance of the base VM. (Suspend/hibernate is not sufficient.)
If you have made major changes (e.g. installing a large service pack), consider taking an additional snapshot now so that you will not have to re-transfer the current snapshot when you make your next update.
Overnight, (a) either reboot each developer machine or programmatically kill the hypervisor process on each developer machine (no, the developers will not remember to close it themelves) and then (b) copy over the changed files using ROBOCOPY /MIR or the like.

Of course, in order for this to work, you will need to transfer all changed files associated with the VM, which may include configuration files containing metadata about the snapshots in addition to the snapshot/delta files themselves. You also will need to ensure that, on each developer machine, the VM is stored in exactly the same location as it is on your own machine.

Rsync: Alternate Approach

An alternative approach would be to use fixed-size virtual disks, no snapshots, and an rsync client/server like DeltaCopy to copy only the changed portions. This is not the preferred approach because:

It would require installing the rsync software on each developer machine.
The actual copy process would take longer, despite no more data being transferred, because rsync would need to analyze the entire virtual disk file file to determine which portions need to be transferred.

Conclusion: You could use rsync for this, but it seems like overkill if your hypervisor supports snapshots.

Best Answer

Related Solutions

Virtual Machines – Safe Range of MAC Addresses for Virtual Machines

How to manage changes to set of cloned Virtual Machines

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