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So you want to build an Ubuntu PXE image? You've come to the right place.

ubuntu-pxe 최신버젼 다운로드

최종 버전 다운로드 (.zip)

// repository documentation

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# How to create Ubuntu Core PXE Image

## Introduction

It's not as easy as it should be to get a simple linux PXE image booting. [Ubuntu Core](https://wiki.ubuntu.com/Core) is a step in the right direction, but we need to do a little work first.

## How it works

The standard ubuntu initrd.img starts it's `init` process, does some init-y things, and hopes by the time it get's to the end of it's processes that something has mounted to /root so it can boot fully to that. Generally grub or something similar will pass boot options that tell it to mount a particular disk.

Unfortunately, there's no option to tell `init` to grab a rootfs from tftp, so we have to get a little crazy. The busybox included in the initrd doesn't have tftp built in, and even if did, busybox tftp is much slower compared to [PXELINUX](http://www.syslinux.org/wiki/index.php/PXELINUX). It's easier just to build the root.img straight into the initrd.img and copy it over to a RAM disk as part of `init`.

In the end you end up with an initrd.img that weighs about 100MB. The majority of that lives in `/lib/modules`, so if you know what you need, you can slim down the image a lot.

## Building the Image

These aren't copy and paste commands. Instead it's more of an outline to put everything together.

# get resources
    mkdir /opt/ubuntu_core
    cd /opt/ubuntu_core
    mkdir root
    wget <core.tgz>
    wget <kernel.deb>
    cp <chroot.sh> ./
    cp <umount.sh> ./
    cp <clean.sh> ./
    cp <build.sh> ./

#create optional deploy.sh to be run after building with build.sh
    vim deploy.sh
    chmod +x deploy.sh

# extract filesystem
    tar xzvfp <core.tgz> -C root

# add dns settings
    vim root/etc/resolv.conf

# put kernel in filesystem
    cp <kernel.deb> root/

# chroot
    # if you encounter errors you may need to mount /proc /sys and /dev into root
    # see chroot.sh code
    ./chroot.sh

# install kernel
    dpkg -i <kernel.deb>

# back out of chroot
    exit

# get kernel and initrd
    cp root/boot/<vmlinuz> vmlinuz
    cp root/boot/<initrd.img> initrd.img

# extract initrd
    cd initrd
    zcat ../initrd.img|cpio -i

# make zcat easily available
    cd bin
    ln -s busybox zcat

# go back to initrd directory
    cd ..

# get mount to ram script
    cp <mount_to_ram.sh> ./

# add "/mount_to_ram.sh" on line before "# Export relevant variables"
    vim init

# go back to main directory
    cd ..

# do anything else you want to do.. install packages etc
    ./chroot.sh

# clean up unneeded files
    ./clean.sh

# build initrd with root.img included
    ./build.sh

## PXE booting

This assumes you already know how PXELINUX works. Just use these two lines in your menu entry:

kernel /path/to/vmlinuz
    initrd /path/to/initrd.img

## Networking

From my research, adding the following line to your menu entry should make you client get DHCP on boot:

append ip=dhcp

In actuality, that only works sometimes. It's not too hard to get it working all the time.

# get to working directory
    cd /opt/ubuntu_core

#chroot
    ./chroot.sh

# install dhcp client
    apt-get update
    apt-get install isc-dhcp-client

# Tell the networking system to give you DHCP
    # Put the following two lines in /etc/network/interfaces
    # auto eth0
    # iface eth0 inet dhcp
    vim root/etc/network/interfaces

# get out of chroot
    exit

# clean up unneeded files
    ./clean.sh

# build initrd with root.img included
    ./build.sh

## Troubleshooting

* Don't run `apt-get upgrade` or risk killing your rootfs with packages not meant to be installed in Ubuntu Core.
* Having trouble installing packages with `apt-get` giving you weird messages? Make sure `/dev`, `/sys`, and `/proc` are mounted. Look at the comments in `chroot.sh` for help.
* `mount_to_ram.sh` creates a RAM disk of `512MB` to copy the rootfs into. If you need more or less just edit that script and rebuild.

## Copyright

All this is straight-up Public Domain.

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