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 (ouch so painful) slower 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 ghost doesn't recognize your file system, or similar. So here's how to do with on-board tools.

If speed is important and you have a Gbit/s connection, copy without compression first, compress on the server later when you have time to spare. On a 100Mbit/s (or worse: wireless 802.1a/b/g/n) connection compression before transfer will usually yield higher performance. Depending on the speed of your PC you should run no compression for (really) ancient CPUs (< 600MHz) , compress for old ones and gzip for current CPUs (Core and newer).

One possible problem you might encounter is that FAT filesystems won't do more than 2GB image size, so choose an appropriate file system type on the server.

Requirements:

• Two or more identical PCs that are supported by the

• Boot media (floppy, CD or USB stick) that can handle the hardware as well as the wanted filesystems, e.g. grml, PuppyLinux or the oldie-but-goldie 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 -l PORT < /dev/null > image.gz
  Some old Netcat versions need the parameter combination "-l -p PORT" as the meaning of the "-p" parameter changed.

• 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 -l PORT

• 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 -l PORT < /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.