Klaus has released the latest version of Knoppix, 3.8, to the crowd at C=
eBIT=20
2005. This version includes the normal round of updates including the 2.6.1=
1=20
kernel by default, KDE 3.3.2, and Firefox and Thunderbird instead of Mozill=
a.=20
The exciting news, however, is the addition of href=3D"http://www.fsl.cs.sunysb.edu/project-unionfs.html">UnionFS. Uni=
onFS=20
stacks your Knoppix ramdisk on top of the read-only filesystem on the CD, t=
he=20
effect being that you can apt-get install, and otherwise modify all of the =
files=20
on the system as though they were all writeable. Here I'll go over why I th=
ink=20
this is going to change Knoppix in a major way.=20

One of the struggles with using Knoppix day-to-day as a portable distrib=
ution=20
has always been the fact that the majority of the CD was read-only. You had=
a=20
nice ramdisk sandbox that let you write within the /home directory, and tin=
ker=20
in /etc if you changed some of the symlinks. If you wanted persistence, the=
re=20
was a nice script that created a small filesystem on writeable media like a=
usb=20
thumbdrive and used it to store your home directory.=20

The Problem

The problem, of course, is that you couldn't install new programs with t=
his=20
method. All of /usr is read-only. Over time various methods have been intro=
duced=20
to try to hack around this by redirecting binaries into the /home directory=
and=20
changing various system paths. The live software installer that came with=
previous versions of Knoppix is one example, and href=3D"http://klik.sf.net/">klik is another. These worked okay, depend=
ing on=20
the program, but in some cases relied on hacks such as using scripts to sea=
rch=20
and replace file paths within binaries.=20

The Solution

Enter UnionFS. With this system, basically every segment of the filesyst=
em is=20
read-write. UnionFS keeps track of which files you have modified (which are=
modified and stored within the ramdisk) and which are unmodified, all on t=
he=20
fly. When you access a file in the filesystem that has been modified, Union=
FS=20
points you to the copy in ramdisk instead of the copy on the CD-ROM. This m=
eans=20
that if you, say, want to install the href=3D"http://www.enlightenment.org/">enlightenment window manager all=
you=20
would need to do is:=20

knoppix-at-2[knoppix]$ sudo apt-get=20
update
knoppix-at-2[knoppix]$ sudo apt-get install=20
enlightenment

You can install programs just like with Debian. They all get installed t=
o=20
their regular locations, and if you check out the /ramdisk directory on the=
CD,=20
you will see a mirror of the root directory structure (or at least the=20
directories that have been modified) and can see all of the files that you =
have=20
changed. You can even use your favorite graphical packaging program (if you=
have=20
one) to install packages.=20

This also means that if you set up a persistent home directory, you can=
potentially back up all of these changes and restore them at boot. In fact=
,=20
Knoppix 3.8 already has a modified persistent home script that does just th=
is=20
(although it's still a beta feature so expect to see bugs here and there).=
Knoppix can even detect when you have done this on a drive when it boots, =
and=20
will let you choose what features to restore from this image (if any). If y=
ou=20
let it time out, Knoppix does the safe thing and doesn't load any of the=20
settings.=20

The latest persistence script also automates the process of setting up a=
n=20
AES256-encrypted home directory, so if you are concerned about the security=
of=20
your persistent image you can enable this option, type in a passcode, and=
Knoppix does the rest.=20

I really think UnionFS is going to take Knoppix to a whole new level of=
ubiquitous computing. You can truly use the CD just like any other install=
ed CD,=20
and with the prices of usb thumbdrives continuing to drop, you can basicall=
y=20
install anything you would like. Major changes, such as replacing KDE with=
Gnome, probably will still work better if you do a full remaster, but I ex=
pect=20
all of the Knoppix-based live CDs (if they are smart) will incorporate this=
technology into future releases.=20

Can you tell that I'm excited about this? Like I said, currently it seem=
s to=20
be a bit buggy (on a few of my machines I seem to get some instability afte=
r I=20
restore from an image), but I imagine that sort of thing will be ironed out=
once=20
the "download version" of Knoppix 3.8 hits href=3D"http://www.knoppix.org/">http://www.knoppix.org.=20

Kyle Rankin is =
a=20
system administrator for The Green Sheet, Inc., the current president of th=
e href=3D"http://nblug.org/">North Bay Linux Users Group, and the author =
of href=3D"http://www.oreilly.com/catalog/knoppixhks">Knoppix Hacks.=20