Remaster Knoppix without Remastering

Kyle Rankin

Sr. Systems Administrator

Author of Knoppix Hacks and Knoppix Pocket Reference

http://greenfly.org/talks/knoppix/remaster.html

Agenda

Traditional Remastering
Remaster without Remastering?
Desktop Persistence Features

Save Configuration
Tweak Save Configuration
Persistent Disk Image

Tweak Boot Settings
Tweak initrd
Custom Boot Scripts
Example: Web Cam

What is Knoppix?

A complete Linux distribution that runs directly from a bootable disc, Knoppix has many uses:

Demonstrate Linux
Portable Linux Distribution
Install Linux
System administration
Rescue disc
Live CD creation
Many other uses

Traditional Remastering

Copy entire Knoppix file system to disk
chroot into file system
Add/remove packages, edit files, etc.
Exit chroot
Create compressed loopback file system
Create and test ISO

Traditional Remastering

Problems:

Time consuming
Complex
Trial and error
Space limitations
Keeping up-to-date
Live CD sprawl

Remaster without Remastering?

Change Knoppix without changing KNOPPIX cloop file
Faster
Simpler
Carry just one disc
Easier to gauge space
Easier to update/migrate

Save Configuration

Classic Knoppix script: saveconfig (or K->Knoppix->Configure->Save Knoppix Configuration)
GUI allows you to save:

Personal configuration (dotfiles, dirs)
All files on Desktop
Network settings
Graphics settings
Other settings (printers, peripherals)

Save Configuration

How it works

Creates configs.tbz compressed tarball on chosen media
Creates knoppix.sh script to extract the tarball
At boot choose myconfig=/dev/sda1 or myconfig=scan
Knoppix executes knoppix.sh at end of boot process
Store different configs in different dirs and use myconfig=/dev/sda1/dirname/

Tweak Save Configuration

Start with already-created configs.tbz and knoppix.sh
Extract configs.tbz in temporary directory, modify, then re-create
Or bypass configs.tbz and make your own:
- BZIP2=-9 tar -cpPjf configs.tbz /home/knoppix/.mozilla

Tweak Save Configuration

To add files:

bunzip2 configs.tbz
tar -rpPf configs.tar /path/to/file

To delete files:

bunzip2 configs.tbz
tar --delete -pPf configs.tar /path/to/file

Then recompress:

BZIP2=-9 bzip2 configs.tar
mv configs.tar.bz2 configs.tbz

Persistent Disk Image

Traditionally for persistent home (mkpersistenthome)
Created loopback disk image for /home
Changed because of AuFS

UnionFS

Background

Created in 2004
Lets you merge filesystems on top of each other
Useful for NFS (server1:/home + server2:/home + server3:/home)
Merge read-only and read-write filesystems
http://www.fsl.cs.sunysb.edu/project-unionfs.html

UnionFS/AuFS

Knoppix with UnionFS/AuFS

Starting with Knoppix 3.8
Ramdisk on top of /
Write anywhere (UnionFS figures it out)
Install packages with apt-get, aptitude, synaptic
Limited by ramdisk
Replaced with stabler AuFS (Another UnionFS) aufs.sf.net

Persistent Disk Image

New script knoppix-mkimage (or K->Knoppix->Configure->Create a persistent Knoppix disk image)
Creates loopback file system with complete copy of /ramdisk
Option for AES256 encryption
At boot automatically detects if present and presents options:

Home: /home)
System: Replaces /ramdisk
Overwrite: Off by default, replaces image /etc if System is enabled with detected settings
Init: Start any persistent init scripts

Cheat code home=/mnt/sda1/knoppix.img

Tweak Boot Settings

Go to boot/isolinux dir on Knoppix disc
isolinux.cfg main configuration file
Change default cheat codes, boot timeouts, add new boot images
Edit boot messages in boot.msg, f2, f3, or add your own

Tweak initrd

cp /cdrom/boot/isolinux/minirt.gz .
gunzip minirt.gz
mkdir temp
mount -t ext2 -o loop minirt ./temp
Edit linuxrc file (add new cheat codes, change default Knoppix paths, etc.)
umount temp
gzip -9 minirt

Custom Boot Scripts

Like with saveconfig, Knoppix will execute KNOPPIX/knoppix.sh if present
Executes at end of boot process
Just a shell script
What's possible?

Add .debs to disc and dpkg -i them in the script
Start non-default init scripts (like sshd or apache)
Just about anything

Example: Web Cam

#!/bin/sh

echo Configuring Apache
cp /cdrom/webcam/index.html /var/www/index.html
/etc/init.d/apache start
echo Configuring Cron
echo '* * * * *  root gqcam -d /var/www/webcam.jpg > /dev/null' 
>> /etc/crontab
/etc/init.d/cron start