Linux netbooting
Instructions follow on how to netboot using Ubuntu Linux.
Client Setup
Create Linux Kernel
To get a kernel up and running it needs firstly to boot itself and then run some file system drivers, or even network drivers in the case of NFS, to allow the file systems to mount and let the operating system boot normally. To do this the kernel needs to mount a RAM disk which contains all the drivers necessary for boot up. This RAM disk is called an initrd file or "initial ramdisk file" Below are the steps to firstly create the kernel with the necessary options then create a ramdisk file with the required drivers and finally configure the server to network boot this kernel
I Build the kernel image
1) Start the kernel configuration program in /usr/src/<linux kernel version>
sudo make menuconfig
2) Set the following options on the kernel configuration menus
Processor type and features --->
Processor family: Pentium-Classic
Device Drivers --->
Networking support --->
Ethernet (10 or 100Mbit) --->
[*] Via Rhine support
Networking options --->
[*] Packet socket
[*]IP: kernel level autoconfiguration
[*] IP: DHCP support
[*] IP: BOOTP support
[*] IP: RARP support
File systems --->
Network File Systems --->
<*> NFS file system support
[*] Root file system on NFS
3) Make the kernel
sudo make
4) Make the kernel image
sudo make bzImage
This will give you your linix kernel image (bzImage) in /usr/src/linux-source-2.6.12/arch/i386/boot/
5) Copy the kernel image to the server
scp bzImage djohnson@meshy.dhcp:~/vmlinuz.david
II Build the initial ramdisk file (initrd)
1) Make the kernel module drivers
sudo make modules
2) Backup your current kernel modules (<current kernel version> is your current kernel e.g. 2.6.10-12
sudo cp -r /usr/modules/<current kernel version> /usr/modules/<current kernel version>.bak
3) Install the module drivers (note this will install all the drivers in the directory /lib/modules/<kernel version> If your current kernel version is the same as the kernel source you are building it will overwrite all your current kernel modules but step 2 would have created a backup - after this process however you will need to restore your original kernel modules using the backup
sudo make modules_install
4) Create the initrd ramdisk image
sudo mkinitrd -o initrd.img-2.6.12 2.6.12
The mkinitrd script does a few default things here. First it looks at /etc/mkinitrd/mkinitrd.conf to see which modules it must include. In the example above it will look in /lib/modules/2.6.12 to find all the modules to build into the initrd.img-2.6.12 file
5) Copy the initrd file to the server
scp initrd.img-2.6.12 djohnson@meshy.dhcp:~
III Setup the server to run the kernel with the initrd file
1) Login to the server containing these files
ssh name@server
2) Copy the kernel and the initrd file to the tftpboot directory
cp vmlinuz.david initrd.img-2.6.12 /export/tftpboot
3) Edit the pxelinux.cfg/defualt file to boot your new kernel
DEFAULT vmlinuz.david APPEND ip=dhcp root=/dev/nfs nfsroot=172.20.1.1:/export/linux/ubuntu ramdisk_size=16432 initrd=initrd.img-2.6.12
Server Setup
Setup DHCP
Setup PXE
Setup Filesystem
Useful information: Building PXE Imager from scratch
I Setup root file system
1) Use debian debootstrap tool to create basic filesystem.
sudo debootstrap breezy /home/yusuf/ubuntu ftp://ftp.is.co.za/ubuntu/
2) Copy the driver modules that were created in the client setup to the filesystem
cp -r /usr/modules/<current kernel version> /home/yusuf/ubuntu/lib/modules
3) chroot into new filesystem
sudo chroot /home/yusuf/ubuntu/
4) Setup a root passwd
passwd password: <enter root password>
5) create apt source list
sudo vi /etc/apt/sources.list
6) Add packages
sudo apt-get update
sudo apt-get install ssh olsrd
7) Tar the filesystem
sudo tar -cvjf ubuntu.tar.gz ./ubuntu/
8) Copy the filesystem to the server and un-tar
scp ubuntu.tar.gz user@server:~
II Create root file system on the server
1) Login to the server containing these files
ssh name@server
2) Untar the root file system to the export directory
tar zxvf ubuntu.tar.gz /export/linux/
3) Restart one of the client machines and check that it boots successfully
How to build a gutsy file system
After chroot into file system
1) Remove udev
apt-get remove udev
2) Get slackware devices
Copy these to root of chroot environemnt
Untar in root
tar zxvf devs-2.3.1-i386-13.tgz /
3) Change the policy of the init
Add /usr/sbin/policy.init.d
- !/bin/sh
exit 101
4) Add locale settings
/var/lib/locales/supported.d/
en local
sudo dpkg-reconfigure locales
5) In you kernel configuraion
Under devices->character devices [*] Unix98 PTY support
Building a linux system from scratch
Adding dropbear support
If you are logging in from bash
change the /etc/passwd file to:
root:x:0:0:root:/root:/bin/bash