Building My Own Boot CD - compressloop loop

[tomslounge]

Reference for this discussion:
http://www.gentoo.org/proj/en/releng/gcloop/#doc_chap5

I have a feeling the person who wrote this doc also writes man pages with examples that do not work.

OK - Goal - custom building a bootable CD for non-profit educational institution

I've scoured the net for detailed information regarding the science of transferring system from initrd.gz (SYSLINUX or ISOLINUX) to a mounted /cdrom which then becomes the root file system.

I followed a trail from Paul's Boot CD
http://www.geocities.com/potato.geo/bootlinuxcd.html (when it works)
back to alll things Gentoo - it seems a few mini-distros with no real purpose in life have adopted cloop, but finding the exact incantation to use these modules seems like a mystery science.

I built me a RHAT 9.0 system as the base build. Why - because it was simple and easier to do than installing Gentoo. I sepnt days building up a Gentoo system, and major problems - too impatient.

I've got it running with all the module support as outlined in the Gentoo docs, and am able to successfully load compressloop.ko, and I have experimented with the instructions as follows - reprinted here with my ignorant questions:

This part is straightforward and simple enuf:
dd if=/dev/zero of=/tmp/image bs=1M count=700
mke2fs /tmp/image


But here's where the wheels fall off... where did we get /tmp/myimage?

mount -o loop /tmp/myimage /mnt/data

Did you mean /tmp/image or really /tmp/myimage?
Why?

cp -pr /tmp/mydata /mnt/data

By /tmp/mydata, you imply an example, i.e some root tree or does it have to be /tmp/mydata, and where did we get /tmp/mydata .

umount /mnt/data

Why did we unmount /tmp/data?

This does indeed work ...

compress_gcloop_ucl -c 10 -b 131072 /tmp/image /tmp/image.ucl

I guess it would be helpful to see a real example.

I have a build environment that is on a drive, which everything under /build.

Here's what I did to try and verbose the script a bit - and perhaps someone can help me understand where I'm screwing it up.

---------------------------

SOURCE=/build/root
RAMBUILD=/mnt/rootbuild
ROOTFS=/build/cdimage/rootfs.ucl
TMPIMG=/tmp/image
umount $RAMBUILD
#
echo " Clearing loop devices - ignore errors ..."
losetup -d /mnt/loop0
losetup -d /mnt/loop1
#
echo " Making directory /mnt/rootbuild for mount point..."
mkdir -p /mnt/rootbuild
#
echo " Using dd and /dev/zero to create a blank ram drive ... "
# Currently only need 80mb for a modified Paul BootCD root tree
dd if=/dev/zero of=$TMPIMG bs=1M count=80
echo " Formating the blank slug ..."
mke2fs -q $TMPIMG
#
echo " Mounting $TMPIMG loop device on $RAMBUILD ..."
mount -o loop $TMPIMG $RAMBUILD
echo $TMPIMG is now mounted on $RAMBUILD and ready for loading ...
#mount
#
echo " Copying from $SOURCE into $RAMBUILD ... "
cd $SOURCE
cp -prv * $RAMBUILD
df -h
#
echo " Unmounting $RAMBUILD ... but leaving new data in the $TMPIMG.loop file ..."
umount $RAMBUILD
#
echo "Compressing $TMPIMG and creating $ROOTFS ... "
compressloop_ucl -c 10 -b 131072 $TMPIMG $ROOTFS

----------------

After that comes trying to understand what is happening at boot time. I noticed Paul's Boot CD hands off control to init, and he uncompresses an 8mb file system using standard gzip extraction, but obviously this won't work using the ucl compression tools.

I built a script to mount a ucl image based upon your docs, and I get an error about specifying the proper file system type when I use your steps:

This is easy enough ...
mkdir /mnt/image
modprobe compressloop

Now this is cryptic enough, using some kind of shortcuts I do not understand with the echo statement. I understand the options, but not sure why encryption would be needed to do a simple mount of the image.

echo " "|losetup -E 19 -e ucl-0 -p0 /dev/loop0 /mnt/cdrom/image.ucl


This does not work without a file system type, i.e "-t ext2" or somthing, which didn't work either.

mount -o ro /dev/loop0 /mnt/image/

I built yet another script to test with to no avail:

-------------------

PATH=/bin:/usr/bin;export PATH
READUCL=/mnt/ucl
UCL=/build/cdimage/rootfs.ucl

echo "Make mountpoint $READUCL ..."
mkdir -p $READUCL

echo " Anal probe ... "
/sbin/insmod /lib/modules/2.6.5/kernel/drivers/block/compressloop.ko
/sbin/insmod /lib/modules/2.6.5/kernel/drivers/block/loop.ko

#/sbin/lsmod
echo " Woah ... "
echo " "|/sbin/losetup -E 19 -e ucl-0 -p0 /dev/loop0 $UCL
echo " Mounting the loop'd $UCL on $READUCL ..."
mount -t ext2 $UCL $READUCL
mount

--------------------------

What I need to know is how to make the image in simple steps, how to hand off from initrd.gz at boot to the ucl image.

Again, I'm building this CD for a school where they want to be able to insert CD, come up into X with specific apps, no toys or the ability to screw up the system - which is why I like the bootable CD concept.

Any help is greatfully appreciated.

I also tried modifying the Pauls' Boot CD to use the new ucl tools to no avail.

----------------------------------------

PATH=/bin:/usr/bin;export PATH
echo "System init"
mount -t proc none /proc
mount -o remount,rw /
echo "Find the extras on the CD and mount it"
if [ -r /dev/cdrom ] ; then
mount -t iso9660 /dev/cdrom /cdrom
fi
cd /

umount /initrd
freeramdisk /dev/ram0

# mkdir /mnt/image
# modprobe compressloop

echo " "|losetup -E 19 -e ucl-0 -p0 /dev/loop0 /mnt/cdrom/rootfs.ucl
mount -o ro /dev/loop0 /

echo "Running ldconfig"
ldconfig
#
CONFIG=/cdrom/config
# Check for auto config files
if [ -f $CONFIG/networkcard ];then
cfgcard `cat $CONFIG/networkcard`
fi
if [ -f $CONFIG/network ];then
cfglan `cat $CONFIG/network`
fi

--------------------


TIA!

tom