[HOWTO] Modding the gentoo minimal livecd (reiser4, kernel)

[hirakendu]

A self explanatory example script for modding the gentoo minimal livecd :

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#!/bin/bash

# This is a (short) example and HOWTO for modifying the gentoo minimal livecd.
# (The example is about creating a reiser4 minimal livecd with our own kernel
# from original minimal livecd.)

# 0) We need about 600 MB of free space.
     cd /tmp/
     mkdir gentoo-min/
     cd gentoo-min/
     wget http://gentoo.osuosl.org/releases/x86/2007.0/installcd/install-x86-minimal-2007.0-r1.iso

#  [[ It is assumed that we have a kernel with reiser4 and squashfs installed
#     (in this example, its 2.6.22-helium9), and also that we have squashfs-tools
#     and reiser4progs :
        emerge -u squashfs-tools reiser4progs
#    ]]


# 1) Extract the livecd contents, the squashfs img contents and initrd contents :
     mkdir iso/ iso-ori/ 
     mount install-x86-minimal-2007.0-r1.iso iso/ -o loop
     cp -a iso/* iso-ori/
     umount iso/
     rm -rf iso/
     cp -a iso-ori/ iso-new/

     mkdir sqfs-old/
     unsquashfs -f -d sqfs-old/ iso-ori/image.squashfs
     cp -a sqfs-old/ sqfs-new/

     gunzip < iso-ori/isolinux/gentoo.igz > gentoo.i
     mkdir initrd-old/
     cd initrd-old/
     cpio -idv < ../gentoo.i
     cd ..
     cp -a initrd-old/ initrd-new/

# 2) Modify stuff :

#   2a) For adding reiser4 support :
     emerge -u gentoolkit
     mkdir -p /usr/portage/packages/
     emerge -u reiser4progs
     quickpkg reiser4progs libaal
     mkdir 1/ 2/
     tar -xjpf /usr/portage/packages/All/libaal-1.0.5.tbz2 -C 1/
     tar -xjpf /usr/portage/packages/All/reiser4progs-1.0.6.tbz2 -C 2/
     cp -a 2/* 1/* sqfs-new/


#   2b) For adding the our own kernel :
     cp /usr/src/linux/arch/i386/boot/bzImage iso-new/isolinux/gentoo
     cp /usr/src/linux/.config iso-new/isolinux/config
     rm -rf initrd-new/lib/modules/
     rm -rf sqfs-new/lib/modules/*
     cp -a /lib/modules/$(uname -r)/  sqfs-new/lib/modules/

#   Note that this assumes that we have all ide and sata and raid related
#   drivers compiled into our kernel (and not as modules). Its also assumed
#   that we have reiser4 and squashfs compiled into the kernel (not as modular).
 
#    [[ 2c) Optional : Additional firmware (for network cards say ;-) -
      cp -a /lib/firmware/* sqfs-new/lib/firmware/
#     ]]

# 3) Merge back :) -
     rm iso-new/image.squashfs
     mksquashfs sqfs-new/ iso-new/image.squashfs

     cd initrd-new/
     find . | cpio --quiet --dereference -o -H newc | gzip -9 > ../gentoo.igz
     cd ../
     cp gentoo.igz iso-new/isolinux/

     cd iso-new/
     echo \#\!/bin/bash >> create_iso.sh
     echo "mkisofs -R -b isolinux/isolinux.bin -no-emul-boot -boot-load-size 4 -boot-info-table -c isolinux/boot.cat -iso-level 3 -o ../livecd.iso . " >> create_iso.sh
     chmod +x create_iso.sh
     ./create_iso.sh
     cd ..

#    Thats it, we have our livecd.iso :D.

# Hirakendu Das
# (20070905)

And here is a resultant livecd :

http://hirakendu.mooo.com/gentoo/gentoo ... 2.6.22.iso

Many thanks to many livecd guides, and to Wainkoko for his excellent kernel patchsets (kamikaze sources) .

[kernelOfTruth]

nice guide, I'll give it a try if I have more time again (around Christmas )

[dusanc]

I'd like to thank you for this livecd. It's the best thing if you manage to corrupt your / partition with reiser4+cryptocompress as I did (played with some experimental patches), because to repair it you need reiser4progs1.0.6, which I believe exist only on your livecd. Everyone else runs 1.0.5 which corrupts cryptocompress partitions.

Thanks a lot. You saved me a lot of nerves and hair

Dushan

PS. Anyone informed why reiser4progs1.0.6 aren't marked stable after 9 months?
Should I fill a bug report?

[kernelOfTruth]

hey ! my livecd versions contain reiser4-progs 1.0.6 too

[dusanc]

Great. Well I skimmed the release notes and missed that.

[hirakendu]

@ dusanc :
thanks for the appreciation. btw, it was a very quick crude hack of the gentoo livecd (reverse engg fun and googling ). and i personally wasn't aware that i have reiser4progs-1.0.6 . (in fact i don't use reiser4 .) aside, i guess there is some on going row about different 'versions' of reiser4progs_106 - portage/namesys/...? (check the reiser4 / 23-kamikaze5 threads).

@ kernelOfTruth :
i must say, i should try out your livecd in the winter break too . (btw, you may not be interested in mine, because its practically as useless as the gentoo minimal disk except for rescue/install . in fact, you have spare bandwidth and don't mind downloading a gorilla, there is a full blown system of mine in a 2 gb livedvd image - http://hirakendu.mooo.com/gentoo/neon-iso/ which you may want to have a look at. and it doesn't support raid/lvm etc.) (ps : given that we both made livedisks, we both appreciate the effort and fun involved . i didn't spend any effort in trimming the system of course, only making it out-of-box. only initrd and linuxrc were the harder parts .)

[cjubon]

Hi hirakendu, thank you for this HOWTO.

With your help, I managed to build my own minimal-install-cd-with-reiser4, but when booting from it, I get

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Kernel panic - not syncing. No init found. Try passing init= option to kernel.

However, I've no idea what init option I should pass to the kernel .

I tried various options, but none worked. I must admit that I do not really understand the process of booting from a cd, so I can only guess. Perhaps one of you gurus out there has a quick solution.

Perhaps I should mention thatin order to boot from this live-cd I have to pass root=/dev/hdb to the kernel due to my specific hardware setup. Further, I appended a version string to the kernel during config (i.e., "-smp-reiser4"), but this doesn't matter, I hope.

Thanks for your advice.

[hirakendu]

Hi.

My first question of interest would be this - hopefully my livecd, unchanged, booted fine .

Coming to your error - init not found, my best guess is that you may not have initrd and initramfs support compiled into the kernel. Also make sure isofs (iso9660 file system used in the cd) is compiled directly into the kernel (not as module). And the other stuff - make sure the necessary stuff like chipset drivers (sata and ata drivers) and filesystems like squashfs and unionfs are compiled in (not modular).
(Typically init is a script, usually named /linuxrc or /sbin/init, inside the initrd which acts like a small compact linux system. The init script performs most of the basic actions like mounting root filesystem etc before the actual system starts.)

Now the other things. Hopefully you have used this script more as a HOWTO than the script itself. Please be careful about specific steps. Especially step 2(b). The kernel image (bzImage, aka vmlinuz) is picked from /usr/src/linux/, so make sure the kernel you are interested in, has sources linked to /usr/src/linux. Also, kernel modules are copied from /lib/modules/, and the the version chosen is the output of 'uname -r', i.e., the currently running kernel. So please make sure your running kernel is the kernel you want, or edit the script to point to that version accordingly.

PS : It will be a little more disconcerting to know that this is a crude script (as you can see) and if something doesn't go right while brewing up the livecd, there will not be any warning/error messages. So its best to test the livecd in a virtual machine (like virtualbox or vmware) before trying out on the main machine.

In livecd, the root is root=/dev/ram0 and that argument root=/dev/hdb shouldn't help. In any case, for recent kernels, if you are not using the old ata drivers and using the new libata driver stack, that would be /dev/sdX (if its a hard drive) or /dev/srX (if its a cdrom drive).

[cjubon]

My first question of interest would be this - hopefully my livecd, unchanged, booted fine .

Indeed, it did! Well done!

Coming to your error - init not found, my best guess is that you may not have initrd and initramfs support compiled into the kernel.

Your first guess was immediately right. I forgot to compile initramfs support into the kernel . Perhaps a little hint in the comments of your script would be helpful for others, too. Although it seems clear, I simply didn't think about it because for normal operation - i mean, booting from a hard disk - gentoo doesn't need it.

The only thing which I still don't understand is why all my IDE devices show up as SCSI. But that's not so important once I've figured out that I have to run fsck.reiser4 /dev/sda9 instead of the "fsck.reiser4 /dev/hda9" I was used to .

Thanks for your work and for your advice.
Cheers, cjubon

[hirakendu]

. So hopefully you managed to create a custom disk for yourself at the end of the day.

[trumee]

This works very well. If this needs to be written to a usb disk, following needs to be done

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isohybrid livecd.iso