[wplug-announce] The Open Pitt, Issue 24
Vance Kochenderfer
vkochend at nyx.net
Tue May 16 08:46:34 EDT 2006
PDF version: <http://www.wplug.org/top/wplug-top024.pdf>
THE OPEN PITT
What's cooking in Linux and Open Source in Western Pennsylvania
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Issue 24 May 2006 www.wplug.org
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In this issue:
Hacking Knoppix, Part 2
April Roundup
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Coming Events
May 17 (Wednesday): General User Meeting, Topic: Cryptography. 6:30pm to
9pm, 5409 Wean Hall, CMU
May 27: Installfest. 10am to 5pm, Newell-Simon Hall 3rd floor
atrium (Perlis Atrium), CMU
The public is welcome at all events
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Hacking Knoppix, Part 2
by Sean Parsons
Sean finishes his adventures with the book _Knoppix Hacks: 100
Industrial-Strength Tips and Tools_ by Kyle Rankin, published by O'Reilly
Media <http://www.oreilly.com/catalog/knoppixhks/>.
Last month, we learned what Knoppix is, some tricks to make it a more
useful desktop system, and how to install it to your hard drive. Now we'll
look at some of the more advanced ways it can be used.
Hack #49: Wipe a Hard Drive
Frequently, second-hand hard drives bought using eBay or at swap meets
contain easily-recoverable sensitive files. Simply deleting the
information isn't enough to keep it from prying eyes. Knoppix comes with a
tool called "shred" to make it more difficult for others to recover data
from an old hard drive that you are getting rid of. To securely wipe your
hard drive, boot into Knoppix and find the partition on your desktop that
you want to shred. Then open a terminal and shred it with this command:
$ sudo shred -n 2 -z -v /dev/hda1
Replace "/dev/hda1" with the partition(s) holding the data you want to
obliterate.
What I used Hack #49 for: A friend of mine just purchased a new computer
and wanted to donate her old PC to a charity. But she didn't want to
donate all her personal data, too. I just gave her a copy of Knoppix and a
photocopy of this hack.
Hack #53: Repair the GRUB Bootloader
There are two popular bootloaders for Linux: LILO and GRUB. GRUB has many
interesting features including the ability to change kernels at boot time.
Sometimes, GRUB gets overwritten when installing Microsoft Windows or by an
accidental installation of LILO to the hard drive's master boot record
(MBR). The procedure to restore GRUB is fairly simple.
First, identify your Linux root partition. In this example the root
partition is "/dev/hda1". Next, while running from your Knoppix live CD,
you'll need to mount the partition with the dev option enabled and with
write permission. If the filesystem is not yet mounted, mount it using the
following command in a terminal.
$ sudo mount -o dev,rw /mnt/hda1
If the filesystem is already mounted, you can remount it with:
$ sudo mount -o remount,dev,rw /mnt/hda1
Once this is done, restore GRUB with the following command:
$ sudo chroot /mnt/hda1 grub-install /dev/hda
What I used Hack #53 for: One of my brothers recently managed to overwrite
his MBR when reinstalling Windows. Thanks to Knoppix, it was easy to
reinstall GRUB and restore his ability to dual-boot.
Hack #94: Create a Customized Knoppix
One reason there are so many Knoppix-based distributions is that they are
so easy to create. With this hack, you will soon be running your own
custom version of Knoppix.
First, boot from your Knoppix CD. Most of the commands you use to remaster
the CD require root privileges; instead of typing "sudo" in front of
everything, click the menu item "KNOPPIX -> Root Shell" to launch a
terminal with root privileges.
Next, you'll need to have a disk space to work in. Set up a partition
formatted with a Linux filesystem. To use the "bootfrom" cheat code (from
Hack #5 last month), make sure you use a filesystem compatible with
bootfrom--I recommend ext2. Plan to have at least 4.5 GB of free space
(you can get away with only 3 GB of space if you have 1 GB of RAM).
Now we should check available RAM, as we need a minimum of 1 GB of physical
memory plus swap space. This is what my system shows when I run "free" in
a terminal:
# free
total used free shared buffers cached
Mem: 321784 317040 4744 0 3812 112888
-/+ buffers/cache: 200340 121444
Swap: 433712 12476 421236
The "total" column only adds up to about 737 MB, so we need to increase
this by creating additional swap space. I chose to do this by making a
swap file to give me an extra 750 MB.
# dd if=/dev/zero of=swapfile bs=1M count=750
750+0 records in
750+0 records out
786432000 bytes transferred in 27.858599 seconds (28229417 bytes/sec)
# mkswap swapfile
setting up swapspace version 1, size = 786427 kB
# swapon swapfile
At this point, you'll need to copy the complete Knoppix filesystem to your
hard drive. Change to the target directory on your hard drive and use the
commands:
# mkdir source
# mkdir source/KNOPPIX
# cp -Rp /KNOPPIX/* source/KNOPPIX
This will take a while (approximately 10 minutes). Next you'll need to
copy your "resolv.conf" file over so that your new Knoppix image can
connect to the Internet.
# cp -f /etc/dhcpc/resolv.conf source/KNOPPIX/etc/dhcpc/resolv.conf
Now "chroot" into the Knoppix directory on the hard drive and mount the
"proc" filesystem.
# chroot source/KNOPPIX
# mount -t proc /proc proc
At this point you can start using apt-get to add and remove various
packages. You can also modify your sources located at
"/etc/apt/sources.list" to be able to install packages that are not
currently in your repositories. Once you are ready to create a CD based on
your changes, clear out the cache of packages you have downloaded to
conserve space:
# apt-get clean
If you intend for your system to fit on a standard CD, try to make sure
your customized filesystem is no bigger than the original. Before exiting
the "chroot" environment, make sure you unmount the "proc" filesystem with:
# umount /proc
Then press Ctrl-D to exit the environment. Here is a quick rundown of the
commands I used to create my master CD filesystem.
# mkdir master
# rsync -a --exclude "/KNOPPIX/KNOPPIX" /cdrom/ master/
# mkisofs -R -U -V "Knoppix Hacks filesystem" -P "Knoppix Hacks"
-hide-rr-moved -cache-inodes -no-bak -pad source/KNOPPIX | nice -5
/usr/bin/create_compressed_fs - 65536 > master/KNOPPIX/KNOPPIX
By far this is the most time consuming command, not just because it will
take you a while to type it in, but because it is compressing your
filesystem. It took me close to 45 minutes to compress it, and you can
safely ignore the warnings it outputs about creating a filesystem that does
not conform to ISO-9660.
Now that you've customized your master directory, you need to update your
MD5 checksums prior to creating your CD image:
# cd master
# rm -f KNOPPIX/md5sums
# find -type f -not -name md5sums -not -name boot.cat -exec md5sums {} \;
>> KNOPPIX/md5sums
# cd ..
Now to create the CD image:
# mkisofs -pad -l -r -J -v -V "KNOPPIX" -noemul-boot -boot-load-size 4
-boot-info-table -b boot/isolinux/isolinux.bin -c boot/isolinux/boot.cat
-hide-rr-moved -o knoppix.iso master/
You now have a new "knoppix.iso" image that you can burn to CD.
What I Used Hack #94 For: I really found myself addicted to this hack. I
kept reusing this and then moved onto remastering Morphix, a Knoppix
derivative. By the time I was done, I had an installable live CD based on
Ubuntu with a GNOME desktop and the ability to use Java, Flash, and listen
to MP3 files. I even managed to include my own personalized desktop theme
that I called p9l.
Conclusion
I've barely touched on the many well thought out and clearly explained
hacks included in this book. This is probably one of the best technical
books I've ever read and so I would strongly recommend it to others as
well.
Sean Parsons has been happily hacking on GNU/Linux for over four years and
is very excited to give back to the community through WPLUG.
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April Roundup
Apr. 1 General User Meeting: Ted Rodgers discussed running Linux on the
PowerPC architecture. Although now being abandoned by Apple, it is still
extensively used in IBM servers and special-purpose embedded devices. He
covered the challenges of booting using Open Firmware and how to set up and
partition a hard drive. Ted also answered questions on accessing PCI and
USB devices, enabling 3D video acceleration, and available applications.
Apr. 29 Special Presentation: Virtualization--which lets a single computer
appear to be several machines, each running an independent operating
system--is today's hot topic. Bob Good of VMware spoke about the uses of
his company's virtualization products for consolidating servers, ensuring
high availability, and disaster recovery. This includes the ability to
migrate a running virtual machine from one machine to another, as well as
central management of all machines.
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The Open Pitt is published by the Western Pennsylvania Linux Users Group
<http://www.wplug.org/top/>
Editors: Elwin Green, Vance Kochenderfer
Copyright 2006 Western Pennsylvania Linux Users Group. Any article in
this newsletter may be reprinted elsewhere in any medium, provided it is
not changed and attribution is given to the author and WPLUG.
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