TFTP server manage netboot kernels

TFTP configuration

TFTP can manage different configurations, up to 1 per host!

This is how a ThinClient (= netBoot client) will retrieve its configuration:

As you can see you have 3 possibilities:

1. MAC @ filter. Configuration file name must be:

• Start with ARP type '01-'
• all in lower case hexadecimal
• dash '-' separators instead of ';'

for example a MAC @ 88:99:AA:BB:CC:DD would search for the filename 01-88-99-aa-bb-cc-dd.

2. IP @ filter. Configuration file name must be:

• host IP / network address in hexadecimal
• all in upper case

e.g. 192.0.2.91 -> C000025B

3. Default configuration

To learn more about all the available option, check out http://www.syslinux.org/wiki/index.php/PXELINUX.

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Prepare NetBoot kernel

Make sure that the server you're gonna use to extract the kernel has all the drivers setup and doesn't need a reboot before starting

== If your client(s) will use some specifics drivers then you MUST install these drivers before going through the following steps.

You need to be very careful, especially if you plan to use some smart-card reader!

Create NetBoot menu | defaults

Now, we have to specify which kernel to use and which distributions are available for NetBoot.

Create the default configuration file:

vim /tftpboot/pxelinux.cfg/default

Put the following:

# Debian 7.x
LABEL wheezy
    kernel images/wheezy/vmlinuz
    initrd images/wheezy/initrd.img

# Ubuntu 14.04
LABEL trusty
    kernel images/trusty/vmlinuz
    initrd images/trusty/initrd.img


# Prompt user for selection
PROMPT 1
# No timeout
TIMEOUT 0

• Each LABEL is a specific configuration that will displayed on the NetBoot menu.
• PROMPT 0 = enable user prompt so you can choose the configuration
• TIMEOUT 0 = timeout (in seconds) before the default option is chosen. 0 == no timeout

Note that I used a reference to "trusty/", that's a folder I need to create later on.

Init Kernel files

Create directories

Create the target kernel folders. You should create 1 folder for each distribution you'd like to provide in NetBoot.

# Debian 7.x
mkdir -p /tftpboot/images/wheezy

# Ubuntu 14.04
mkdir -p /tftpboot/images/trusty

Prepare initramfs to boot over NFS

This step must to be run on the machine that has the kernel you are going to serve to your clients.

>>> In our case it has to be run on the TFTP server

Copy initramfs settings for PXE boot

cp -r /etc/initramfs-tools /etc/initramfs-pxe

Adjust PXE boot configuration

cd /etc/initramfs-pxe/
vim /etc/initramfs-pxe/initramfs.conf

Add / adjust the following options:

BOOT=nfs
MODULE=netboot

Copy and prepare kernel

You have to copy your current kernel files to the boot folder:

# Debian 7.x
cp /boot/vmlinuz-`uname -r` /tftpboot/images/wheezy/vmlinuz
cp /boot/initrd.img-`uname -r` /tftpboot/images/wheezy/initrd.img

# Ubuntu 14.04
cp /boot/vmlinuz-`uname -r` /tftpboot/images/trusty/vmlinuz
cp /boot/initrd.img-`uname -r` /tftpboot/images/trusty/initrd.img

Enable NFS boot on target kernel:

mkinitramfs -d /etc/initramfs-pxe -o /tftpboot/images/trusty/initrd.img

Adjust rights:

chmod -R 755 /tftpboot/images/

Notes:

• Do NOT use some symlink for "vmlinuz" and "initrd.img" !! It won't work.

• If you don't want to use `uname -r` [current kernel version and architecture] then adjust the values to target kernel number + architecture

• You have to run mkinitramfs for each kernel you'll provide

• Don't forget to adjust the rights to 755 for every distribution

Kernel modules and source

-- This is an optional step ; but it can avoid many bugs --

If you're using a local kernel as the default NetBoot kernel, then you need to do copy the modules + kernel source to every distribution.

# Copy kernel modules
cp -r /lib/modules/`uname -r` /nfs/trusty/lib/modules

# Copy kernel sources
cp -r /usr/src/linux-headers-`uname -r` /nfs/trusty/usr/src

Note that you have to adjust the /nfs/XXX