Booting aptosid over a network (network block device - nbd)

Warning: dnsmasq includes a dhcp server which can conflict with an existing dhcp server on your network (your router may provide one). The safest option is to only use one dhcp server on any network. This means you should disable any other dhcp servers on the same network. The dnsmasq proxy options outlined below should be able to co-exist with another dhcp server on the same network, however please do not try this unless you administer the network and are ready to deal with any unforeseen consequences which might crop up.

The basics

Network booting first requires that you have a machine capable of network booting, which can be connected via a network you run, to a machine which you can setup to offer the network booting services.

You do not want to do this on your workplace network, or any other network you do not control, unless you run that network or get permission and guidance from those who do. If you are co-operating in a larger network you can investigate all the options to dnsmasq, such as limiting the interfaces it listens on or the clients it will respond to, to restrict the impact of your setup on the network.

The prerequisites

A 2009-04 (or newer) aptosid iso booted up to use as the network boot server. The instructions should be basically the same with any up to date aptosid or debian sid machine and should provide all the clues you need to use on other systems. Linux is required to serve nbd devices.

dnsmasq will be used to provide everything for the initial booting phases, again it shouldn't be hard to translate the required knowledge to other software.

apt-get install nbd-server dnsmasq

Setting up the nbd-server

Presuming the iso can be found at /dev/scd0, (which it probably can be if you booted from cd, otherwise substitute in any suitable file or device), then you can setup a nbd-server conf file called nbd-aptosid.conf with a section called aptosid-iso to export the cd by running the following:

echo '[generic]' > nbd-aptosid.conf
nbd-server /dev/scd0 -o aptosid-iso >> nbd-aptosid.conf

The generic header is always required. If you want to setup the nbd-server to work automatically on a real system you will probably want to setup /etc/nbd-server.conf instead. There are a lot more options to nbd-server than shown here, see man nbd-server.

To actually start the server now, as a normal user and without bothering setting up or copying the file to /etc/nbd-server.conf, you can just run:

nbd-server -C nbd-aptosid.conf

The target of the nbd-server does not have to be an iso or a cd/dvd/usb stick, it just has to contain a suitable filesystem image.


The following example assumes you are running on a simple network where your machine has one ethernet connection which is setup by dhcp from another machine and which the network boot clients can use to setup their interfaces by dhcp.

The main relevant options for dnsmasq to network boot aptosid are to setup a path for the tftp server files and a file for it to boot from there.

Create a tftp directory for booting in /home (you can create it where you want if you prefer another place). Thus the path becomes /home/tftp.

Next create a file called pxe-aptosid.conf and paste in the following:

pxe-service=x86PC, "boot linux", pxelinux

When using the dhcp proxy you need to provide a pxe menu with pxelinux as the only entry which will therefore start it automatically. This is what the lone pxe-service item is above.

As root, move the newly created pxe-aptosid.conf file to /etc/dnsmasq.d/:

mv pxe-aptosid.conf /etc/dnsmasq.d/

Note: For a network (e.g. 192.168.0.*) with no other dhcp server you could swap the first two lines for:


To give out ip addresses starting with and ending with with a lease time of an hour, and to provide the filename to just run pxelinux.0 as part of the dhcp request (when using the proxy you instead provide a pxe menu with only pxelinux as an entry which will therefore automatically start it). This probably won’t setup your network as you wish though unless your dnsmasq server should also be your dns server and gateway for the boot clients.

To enable the new file you will need to uncomment the conf-dir=/etc/dnsmasq.d setting at the bottom of /etc/dnsmasq.conf and then restart dnsmasq.

dnsmasq has a lot of options and can act as a dns server as well as a dhcp, pxe and tftp server. The above is simply a minimal outline of the pieces needed to use pxelinux.


tftp is the network equivalent of the boot directory. Using the continuing example of the /home/tftp directory you need to populate it. If the cdrom is mounted on /fll/scd0:

cp /fll/scd0/boot/isolinux/* /home/tftp
mkdir /home/tftp/pxelinux.cfg
mv /home/tftp/isolinux.cfg /home/tftp/pxelinux.cfg/default
mkdir /home/tftp/boot
cp /fll/scd0/boot/vmlin* /fll/scd0/boot/initr* /fll/scd0/boot/memtest* /home/tftp/boot/
cp /usr/lib/syslinux/pxelinux.0 /home/tftp/
# required for the tftp-secure option to dnsmasq
chown -R dnsmasq.dnsmasq /home/tftp/*

Now you can edit boot options to your satisfaction in /home/tftp on both the pxelinux.cfg/default and the gfxboot.cfg file.

In particular it is suggested that under the [install] section you set the install= to install=nbd, install.nbd.server to the server's IP on the network and install.nbd.port to the name of the nbd export section, for example. aptosid-iso (as nbd exports are named now rather then simply using port numbers).

Alternatively you could disable the F3 menu completely and edit the kernel command lines to use something like:

fromhd=/dev/nbd0 root=/dev/nbd0 nbdroot=,aptosid-iso nonetwork
toram boot code

If you add toram to the boot options, machines with enough ram will release the server as soon as they copy the file and machines without sufficient ram will carry on and boot normally. At least 1 gig of ram, (ideally 2 gig or more), is required for toram.

Network booting

Ensure that the client PC's BIOS is set to use Boot from Network.

As long as your bios supports booting from the network, the machine is connected to a network with your server and the aptosid kernel and initrd.img support your network card, you should be able to boot aptosid from the network.

Some network cards may require non-free firmware which will require rebuilding the initrd image to include the firmware.

Page last revised 03/04/2013 0100 UTC