Overview

 We developed an automatic update system that makes the computer cloning and later the updates much easier. The aim was to facilitate the work of the system administrators by this tool and increases the chances of success of this project.

Prerequisites

The update system needs two servers:

1. The master is the computer where the initial Windows configuration is installed with the VirtualBox drive included. It is advisable that this computer is similar to the ones in the computer rooms where the system will be cloned, especially the processor type is of importance. A separate linux partition comes in handy when one has to copy the windows images, but a network boot solution is also viable.
2. A linux server which will provide services for the install system but it can be freely used for other purposes as well, so it does not need to be a dedicated server. Alternatively the listed services can be installed on multiple computers as well. It is important that it must have enough disk space to hold the zipped images (~20GB). The list of used services is the following:
   • DHCP: For network boot, and IP allocation
   • tftp: For network boot
   • NFS: For the diskless network boot
   • BIND/NAMED: name server
   • HTTP: to download the images

The clients on which we want to install the images the network boot (PXE) must be enabled.

Update procedure

1. The master should be carefully installed and set to meet the requirements of the computer room, with a well configured VirtualBox service. One has to pay attention to read and write permissions, especially concerning the VirtualBox service.
2. The Microsoft sysprep must be installed and executed on the muster, which is then rebooted in linux. In linux we can copy the disk images into files by ntfsclone. We use gzip compressed files as in general the network is the bottleneck. The images should be copied to the HTTP server. (scripts performing this job are included in the distribution)
3. On the HTTP server a new configuration file should be created with the md5 sums of the new images. The configuration will be signed to ensure integrity. (scripts included)
4. Change the tftp server to networked boot
5. Switch on the computers to be installed useing PXE boot. They should install everything automatically.
6. After all computers downloaded the images switch back to local boot and reboot the machines by exiting the cloning (optionally this can be done automatically)

Description of the cloning

The computers boot over the network using nfsroot (the image is supplied in the distribution) and after the short boot it downloads the new configuration file. Checks the signature and compares it to the one stored on the computer (the present state). Then it determines which partitions should be updated.

If all partitions are changed then the partition table is recreated, otherwise it is left intact (in the case if you want to preserve user data during an academic year). Then images are downloaded, unzipped and written to the hard disk in one single command.

In some cases there is a need to modify the sysprep.inf file whichcan be done ofter the windows image installation. Currently in our setup we set the computer name.

On success the new configuration file is copied to the local hard disk, the grub updated and the computer is ready to reboot (or rebooted).

If no partitions need update than the system is rebooted.