[K12OSN] making a live CD...?

Harish Pillay h.pillay at ieee.org
Sun Nov 13 06:00:58 UTC 2005

I was looking at the k12ltsp site and I was not able to find
any guidance on the following, so I will do my bit to help
document it.

> using X-CD-Roast  how do I get this iso image onto
> my drive and then burned onto disks....forgive the
> basic lesson but I have already made several non
> functioning disks and I have one or two people I've
> convinced to try linux but they are getting suspicious
> when I can't even burn a CD for them.......

May I suggest that before actually buring the CD from the ISO
image, you do the following:

a) check the md5 of the image to ensure that the copy is
correct.   MD5 (message digest 5) is based on the RFC
1321 - http://www.faqs.org/rfcs/rfc1321.html.

On a Linux machine, from the commandline, run:

             md5sum -c filename.iso.md5

the filename.iso.md5 is or a file that contains the md5
of the iso is generally on the download site.  The md5
is a mathematical computation of the "signature" of the
file which should match what it is on the download site.

For example, at:

you will see a file: MD5SUMS

That file has the following:

184719032fdee80af3049d93cee2e720  K12LTSP-4.4.1-disc1.iso
1cde79aa252f16db5c75d7542ed19fdd  K12LTSP-4.4.1-disc2.iso
9c445da80306078acb53026564027d1c  K12LTSP-4.4.1-disc3.iso
c56765b41fc48eb3a7020e71af61aead  K12LTSP-4.4.1-disc4.iso
ad85496d8dd27cc18fe576571f822f23  K12LTSP-4.4.1-disc5.iso

So, if you dowloaded K12LTSP-4.4.1-disc1.iso, you can test if
the md5sum of that file is OK.

First, you must make sure that the ISO is in the same directory
as the  MD5SUMS file is residing and you then run:

md5sum -c MD5SUMS

The md5sum command will go through all the entries in the file
MD5SUMS and compute the md5sums of the respective filenames
mentioned and compare.  If the comparision check out, you are
pretty much sure that the download was successful.

b) After download, you might want, on a Linux machine, run the
ISO within a qemu session.

For example, you can invoke the iso as such:

qemu -cdrom filename.iso

the '-cdrom' is the flag sent to qemu to tell it to expect a cdrom
image.  In this case, the filename.iso is a cdrom image.  Naturally,
you can also use qemu to run an actual cdrom via:

qemu -cdrom /dev/hdc

where /dev/hdc happens to be the physical cdrom.

This method is especially useful for live CDs because you are
expected to run everything off the CD and before you cut the CD, it
is very helpful to have it checked first.

Using qemu has saved me a lot of grief and reduced to zero the
waste in bad cdroms.

Naturally, you can test non live CDs as well but  you cannot go far
with qemu unless you intend to install the CD in a qemu environment.

QEMU is a system similar to VMware.

c) If you are using Linux, you can initiate the download of large files
using wget or curl.

With wget, do the following:

wget -c -b ftp://somesite.somewhere.org/pub/filename.iso

what happens is that a log file gets created called wget-log (or
wget-log.N where N is 1, 2 ... in case there is already a wget-log
in the directory where the wget is being executed from).

You can watch the download progress by using tail:

tail -f wget-log (or whatever the wget-log.N is).

The nice thing about this is that should the download fail and you
have already downloaded a bunch, you can resume from where
you stopped.  Saved me a lot of time. You just redo the wget
command from the same directory as where the partial download
was and you can save the work done.

Hope this helps.
Harish Pillay

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