Debian LiveCD

Introduction

• Sometimes we need to boot Linux without HDD e.g. if you want to experiment with HDD encryption, enable/disable it without causing damage to your data. For such cases we need a LiveCD which doesn't mount HDD at boot.

Creating Initial System with debootstrap

apt-get install debootstrap

mkdir livecd

debootstrap --arch powerpc squeeze /root/livecd http://ftp.us.debian.org/debian

# Grab a beer and reverse some PS3 stuff in the meantime :)

# Enter chroot environment

mount -t proc none /root/livecd/proc
mount --rbind /dev /root/livecd/dev
LANG=C chroot /root/livecd /bin/bash

export TERM=xterm-color

echo "debian" > /etc/hostname

dpkg-reconfigure tzdata

# Configure network interfaces

cat /etc/network/interfaces
---
auto lo
iface lo inet loopback

allow-hotplug eth0
iface eth0 inet dhcp

allow-hotplug wlan0
iface wlan0 inet dhcp
    wpa-ssid ssid
    wpa-psk psk
-EOF-

# Configure APT

cat /etc/apt/sources.list
---

deb http://ftp.us.debian.org/debian squeeze main
deb-src http://ftp.us.debian.org/debian squeeze main

deb http://security.debian.org squeeze/updates main
deb-src http://security.debian.org squeeze/updates main
-EOF-

aptitude update

aptitude install locales
dpkg-reconfigure locales
aptitude install console-data
dpkg-reconfigure console-data

tasksel install standard
aptitude install binutils gcc make git vim openssh-server sudo wireless-tools wpasupplicant libssl-dev
aptitude  install gcc-spu g++-spu newlib-spu spu-tools

# Make SSH server start at boot so we could ssh to our LiveCD

update-rc.d ssh defaults

aptitude clean

rm -f /etc/udev/rules.d/70-persistent-net.rules

Creating Root Filesystem

cd /root/livecd
mksquashfs * ../root.sfs

Modifying Root Filesystem

cd /root
unsquashfs root.sfs
cd squashfs-root

# Make your changes

mksquashfs * ../root-changed.sfs

Linux 3 Kernel

• We need a Linux 3 kernel with overlayfs support so we could create a tmpfs over our read-only base filesystem.
• At the moment overlayfs is not supported on Linux 3.5 so it leaves us with Linux 3.4 which doesn't really matter because all my Linux 3 drivers are supported on Linux 3.4 just fine.
• Furthermore, we want to compile PS3 HDD driver as module because in this case we can easily change HDD region flags.

See my GIT repos:

• http://gitorious.ps3dev.net/ps3linux/kernel-configs
• http://gitorious.ps3dev.net/ps3linux/kernel-patches-34
• http://gitorious.ps3dev.net/ps3linux/livecd-initramfs

Initramfs

See my GIT repo: http://gitorious.ps3dev.net/ps3linux/livecd-initramfs

BusyBox

• We need a couple of user-space applications to mount filesystems, load kernel modules and so on.
• And make sure you compile BusyBox without any library dependencies.
• I compiled my BusyBox executable on PS3 Linux but you could cross-compile it too but then you need a complete PowerPC toolchain with libc.

http://busybox.net/downloads/busybox-1.20.1.tar.bz2

tar xvjf busybox-1.20.1.tar.bz2
cd busybox-1.20.1
make menuconfig
make

Creating Image

# Populate initramfs

mkdir initramfs
cd initramfs
mkdir -p bin dev etc lib/modules/3.4.9 mnt proc sbin sys usr/bin usr/sbin

cp ~/busybox-1.20.1/busybox bin/
cd bin
ln -sf busybox sh
cd ..

echo 'sda.*	0:6	0660' >> etc/mdev.conf
echo 'sr[0-9]	0:6	0660	@ln -sf $MDEV cdrom' >> etc/mdev.conf

cat >etc/modules <<EOF
> fat
> vfat
> isofs
> crc-ccitt
> crc-itu-t
> lzo_compress
> udf
> squashfs
> overlayfs
> ps3_gelic
> ps3stor_lib
> sg
> ps3rom
> usb-common
> usbcore
> ehci-hcd
> ohci-hcd
> usb-storage
> EOF

for mod in fat vfat isofs crc-ccitt crc-itu-t lzo_compress udf squashfs overlayfs \
           ps3_gelic ps3stor_lib sg ps3rom usb-common usbcore ehci-hcd ohci-hcd usb-storage; do
    path=`find  /home/glevand/linux-3.4.9-build/lib/modules/3.4.9 -name $mod.ko`
    cp $path lib/modules/3.4.9/
done

# Create initramfs

find . | cpio -H newc -o > ../initramfs.cpio
cd ..
cat initramfs.cpio | gzip > initramfs.cpio.gz

Images

• vmlinux-3.4.9.xz: http://www.multiupload.nl/9C1XVAB3RU (MD5 c15903c28b4eaff3524f3c32f491e25e)
• root.sfs: http://www.multiupload.nl/NERXNME3JJ (MD5 e2ed20d27092105961507de5d7b49ed3)
• Tools available on the root filesystem: gcc, spu-gcc, spuisofs, spuldrfs, ps3vuart-tools, ps3sed and all my other PS3 Linux drivers. Everything you need to compile and test various PS3 stuff.
• In case someone still hasn't figured it out yet, password for root is root and password for glevand is glevand :)
• I enabled DHCP on Ethernet.
• You could use WLAN too but for that you have to modify the root filesystem and configure your SSID and PSK in /etc/network/interfaces.

USB

• Your USB drive should be formatted with FAT32 filesystem.
• initramfs.cpio.gz: http://www.multiupload.nl/KROXJ799N6 (MD5 8da82022b1c2541dc419619e710a0a3f)
• Create debianlive directory on your USB drive.
• Put vmlinux-3.4.9 (extract xz archive), initramfs.cpio.gz and root.sfs into this directory.

$ ls -l /mnt/usb/debianlive/
total 257696
-rwxr-xr-x 1 root root   6746154 Aug 18 17:44 initramfs.cpio.gz
-rwxr-xr-x 1 root root 249835520 Aug 18 17:15 root.sfs
-rwxr-xr-x 1 root root   7288832 Aug 18 17:31 vmlinux-3.4.9
$ ls -l /mnt/usb/
-rwxr-xr-x  1 root root      188 Aug 18 17:30 kboot.conf

• And create kboot.conf in the root directory of your USB drive with this content:

debianlive=/debianlive/vmlinux-3.4.9 initrd=/debianlive/initramfs.cpio.gz

CDROM

• initramfs.cpio.gz: http://www.multiupload.nl/60CNXOU5U0 (MD5 8aa930e1e2e8b99ed223ad1df02ba54e)
• debianlive.iso.xz: http://www.multiupload.nl/HRJFPL38W8 (MD5 f6c9fa8d179f8da6ee196943a841efe9)

mkdir -p iso/debianlive
cp root.sfs initramfs.cpio.gz vmlinux-3.4.9 iso/debianlive
echo "debianlive=/debianlive/vmlinux-3.4.9 initrd=/debianlive/initramfs.cpio.gz" > iso/kboot.conf
cd iso
mkisofs -R -J -l -o ../debianlive.iso .
cd ..

sudo cdrecord -v dev=/dev/sr0 blank=fast
sudo cdrecord -v dev=/dev/sr0 debianlive.iso

Links

• http://securityfocus.eu/?p=149