How to duplicate a complete PC via network

This documentation started in 2001 when standard hard discs often still were measured in MB (MegaBytes) instead of GB. For today's discs approaching TerraBytes you'll need a sufficiently sized network: transferring TBs we're talking about hours or days when using a 1 Gbit/s or 100 Mbit/s network. Likewise it now is completely unpractical to use it as backup means for bigger partitions (e.g. like images on DVDs). For a pure system backup filesystem-aware images like partimage, g4u, Norton Ghost or similar are better due to their reduced image size.

In contrast to these DD still is superiour when it comes to creating a forensic image. Or when the ghoster doesn't recognize your file system, or similar. So here's how to do with on-board tools.

Depending on the speed of your PC you should run no compression for (really) low performance CPUs (< 600MHz), compress for medium sized and gzip for CPUs > 2GHz.. Alternatively you could leave out the compression and store uncompressed images - if you have enough hard disk space and a fast network, that is. One problem is that GZIP won't do more than 2GB image size, so beware...

Requirements:

• Two or more identical PCs that are supported by the

• Boot media (floppy or CD) that can handle the hardware as well as the wanted filesystems, my recommendations: Knoppix CD in text mode (http://www.knoppix.org/) and TRBT floppy (http://www.toms.net/rb/). Make sure you're logged in as ROOT user.

• Optonal an "image server" for central storage of the (different) image files - thus need for enough disk space.

• Network infrastructure for the PCs - a simple crosslink cable often is enough - is using an image server, a switched environment is preferrable.

• The netcat program - usually it is called "netcat", but some other distributions call it "nc"

• If your harddisc is broken, use "dd_rescue" (http://www.garloff.de/kurt/linux/ddrescue/ which will skip read errors. This way you can (try to) rescue data from a broken disc when simple TARing won't do anymore.

Create the image:

• Install and configure the master PC (i.e. the PC to be imaged)

• Cleanup the disk space for each partition used for better compression, e.g. using:
  dd if=/dev/zero of=empty.tmp bs=1024 count=FREEBYTESCOUNT
  rm empty.tmp

• Start command on the image server to accept the image on an arbitrary TCP port (usually above 1024):
  netcat-v -w 120 -p PORT -l < /dev/null > image.gz

• Within 120 seconds start sending the image from the master PC to the image server:
  dd if=/dev/hda bs=512 | gzip -c | netcat-v -w 60 SERVERIP PORT

Flatten the "virgin" PC and impress the image:

• WARNING! This will utterly destroy each and all data on the PC involved!

• Boot with independent media and configure the network

• Prepare the image server to send the image:
  cat image.gz | netcat-v -w 120 -p PORT -l

• Fetch image and impress it onto the PC's harddrive:
  netcat-v -w 60 SERVERIP PORT < /dev/null | gzip -dc | dd of=/dev/hda bs=512

• Reboot and accept the complaining FSCK which will run and correct without problems.

Copy PC On-the-Fly without using an image server

• WARNING! This will utterly destroy each and all data on the PC involved!

• Boot client with independent media and configure the network

• prepare the client to accept the image and write it directly to the disk:
  netcat-v -w 120 -p PORT -l < /dev/null | gzip -dc | dd of=/dev/hda bs=512

• Send the image from the master:
  dd if=/dev/hda bs=512 | gzip -c | netcat-v -w 60 SERVERIP PORT

• Reboot and accept the complaining FSCK which will run and correct without problems.