Ubuntu "Live / Install CD" from existing system

A. Prepare the environment:

1. Set the variables:

export WORK=~/work
export CD=~/cd
export FORMAT=squashfs
export FS_DIR=casper

2. Create the CD and the WORK directory structure:

sudo mkdir -p ${CD}/{${FS_DIR},boot/grub} ${WORK}/rootfs

3. Install packages on the source system:

sudo apt-get update
sudo apt-get install mkisofs grub squashfs-tools linux-headers-$(uname -r)

B. Copy existing installation into the new filesystem:

sudo rsync -av --one-file-system --exclude=/proc/* --exclude=/dev/*\ --exclude=/sys/* --exclude=/tmp/* --exclude=/home/*\ --exclude=/lost+found / ${WORK}/rootfs

If you have a separate boot partition you will have to copy it using the following command:

sudo cp -av /boot/* ${WORK}/rootfs/boot

Copy custom settings:

cp -r /home/yourusername/.config /home/yourusername/.xscreensaver /root/work/rootfs/etc/skel/

C. Chroot into the new system and modify it:

1. Chroot into the copied system after mounting proc and dev:

sudo mount -o bind /dev/ ${WORK}/rootfs/dev 
sudo mount -t proc proc ${WORK}/rootfs/proc
sudo chroot ${WORK}/rootfs /bin/bash

2. Now you are within the chroot environment, type the following commands:

LANG= 
apt-get update 
apt-get install casper discover1 xresprobe

"casper" contain the live scripts. "discover1" & "xresprobe" are used for autodetecting hardware at startup.

3. (Optional) If you want your live cd to have an installer, install the Ubuntu installer:

apt-get install ubiquity

4. (Optional) Install any packages you want to be in the CD with "apt-get".

5. Update the modules.dep and initramfs:

depmod -a $(uname -r)
update-initramfs -u -k $(uname -r)

The initramfs is reponsible for much of the preparation required at the boot time of the CD/DVD. The updated initramfs now contain the live scripts installed with casper.

6. Remove non system users: (script)

for i in `cat /etc/passwd | awk -F":" '{print $1}'`
do
        uid=`cat /etc/passwd | grep "^${i}:" | awk -F":" '{print $3}'`
        [ "$uid" -gt "999" -a  "$uid" -ne "65534"  ] && userdel --force ${i} 2>/dev/null
done

Non-system users are users created by you that have user id more than 999.

7. Delete these files: (script)

for i in "/etc/hosts /etc/hostname /etc/resolv.conf /etc/timezone /etc/fstab /etc/mtab /etc/shadow /etc/shadow- /etc/gshadow  /etc/gshadow- /etc/gdm/gdm-cdd.conf /etc/X11/xorg.conf /boot/grub/menu.lst /boot/grub/device.map"
do
        rm $i
done 2>/dev/null

These files are not needed in the CD/DVD. some of them are could interfer with the CD/DVD boot process. (e.g. shadow and gdm.conf-custom can interfere with autologin).

8. Cleanup the chroot environment: 

apt-get clean 
find /var/run /var/log /var/mail /var/spool /var/lock /var/backups /var/tmp -type f -exec rm {} \;
rm -r /boot/*.bak /tmp/* /home/* /root/* 2>/dev/null

9. If you are using GDM recreate it's config file:

[ -f "/etc/gdm/factory-gdm.conf" ] && cp -f /etc/gdm/factory-gdm.conf /etc/gdm/gdm.conf 2>/dev/null

A customized /etc/gdm/gdm.conf can interfere with the live CD/DVD autologin.

10. Create needed log files in /var/log: (script)

for i in dpkg.log lastlog mail.log syslog auth.log daemon.log faillog lpr.log mail.warn user.log boot debug mail.err messages wtmp bootstrap.log dmesg kern.log mail.info
do
        touch /var/log/${i}
done

Most of these files are log files that have been cleaned in step 7. We created an empty files in their place to prevent the system from complaining at boot.

rm /usr/lib/ubiquity/apt-setup/generators/50cdrom

(Optional) If you want the Installer Icon removed from the final system's Desktop:

rm /usr/share/applications/ubiquity-gtkui.desktop

11. Exit chroot

exit

D. Prepare The CD directory tree:

1. Copy the kernel, the updated initrd and memtest prepared in the chroot:

sudo cp -vp ${WORK}/rootfs/boot/vmlinuz-$(uname -r) ${CD}/boot/vmlinuz 
sudo cp -vp ${WORK}/rootfs/boot/initrd.img-$(uname -r) ${CD}/boot/initrd.gz
sudo cp -vp ${WORK}/rootfs/boot/memtest86+.bin ${CD}/boot

2. Generate manifest:

Note: This step is only needed if you installed the Ubuntu installer ubiquity. This step generates two files (filesystem.manifest & filesystem.manifest-desktop).

sudo chroot ${WORK}/rootfs dpkg-query -W --showformat='${Package} ${Version}\n' | sudo tee ${CD}/${FS_DIR}/filesystem.manifest
sudo cp -v ${CD}/${FS_DIR}/filesystem.manifest{,-desktop}
REMOVE='ubiquity casper user-setup discover1 xresprobe os-prober libdebian-installer4'

(script)

for i in $REMOVE
do
        sudo sed -i "/${i}/d" ${CD}/${FS_DIR}/filesystem.manifest-desktop
done

These two files are used by the ubiquity installer when installing to harddisk. These two files are just lists of packages. Ubiquity compares these two files and removes packages unique to filesystem.manifest. This way when installing to harddisk, packages like casper which is only useful in a live CD/DVD are removed. These packages that will be removed at install are defined in the variable $REMOVE

3. Unmount bind mounted dirs:

sudo umount ${WORK}/rootfs/dev ${WORK}/rootfs/proc

4. Convert the directory tree into a squashfs:

sudo mksquashfs ${WORK}/rootfs ${CD}/${FS_DIR}/filesystem.${FORMAT}

Note: Make sure the resulting file size can fit into your live media.

5. Make Grub the bootloader for the CD

Copy grub file:

sudo find /boot /usr/lib/grub/ -iname 'stage2_eltorito' -exec cp -v {} ${CD}/boot/grub \;

Make the menu.lst

sudo nano ${CD}/boot/grub/menu.lst

Adjust and copy the following text into it and save it:

# By default, boot the first entry.
default 0

# Boot automatically after 30 secs.
timeout 30

title                System (Graphical Mode)
kernel                /boot/vmlinuz BOOT=casper boot=casper nopersistent rw quiet splash
initrd                /boot/initrd.gz

title                System (Safe Graphical Mode)
kernel                /boot/vmlinuz BOOT=casper boot=casper xforcevesa rw quiet splash
initrd                /boot/initrd.gz

title                Linux (Text Mode CLI)
kernel                /boot/vmlinuz BOOT=casper boot=casper nopersistent textonly rw quiet
initrd                /boot/initrd.gz

title                Memory Test
kernel                /boot/memtest86+.bin

title                Boot the First Hard Disk
root                (hd0)
chainloader +1

6. Calculate MD5:

cd $CD && find . -type f -print0 | xargs -0 sudo md5sum | sudo tee ${CD}/md5sum.txt

E. Build the CD/DVD

1. Make the ISO file:

sudo mkisofs -b boot/grub/stage2_eltorito -no-emul-boot -boot-load-size 4 -boot-info-table -V "MY_LIVE_CD" -cache-inodes -r -J -l -o ~/my-live-install-cd.iso $CD

2. Burn your new created ISO!