Among about 95% of Linux iso meant to be booted from a CD or DVD will have the de facto boot loader called isolinux, written by Peter Anvin. It has a configuration file called isolinux.cfg. The isolinux syntax is very similar to Grub and so one can substitute isolinux with Grub.

Isolinux can also multi-boots. I am just more comfortable with grub and know it can deliver what I want. Grub is preferred because we can communicate with Grub during boot time and correct any mistake as we go along. That is very useful with a read-only DVD. Isolinux does not offer this flexibility.

Grub has only one file for booting a CD or DVD. This file is called stage2_eltorito available in every Linux that has Grub. It is stored in /boot/grub or /grub directory. The Grub Manual has steps showing how to create a CD or DVD booted by stage2_eltorito. http://www.gnu.org/software/grub/manual/grub.html#Making-a-GRUB-bootable-CD_002dROM

This is just a big folder for storing several iso files. The iso files have to be expanded first into the normal format first. I use an existing directory in /abit ,rounded up 7 iso files and created the following subdirectories

mkdir /abit/iso
mkdir /abit/iso/DSL-boot
mkdir /abit/iso/slax-boot
mkdir /abit/iso/mepis-boot
mkdir /abit/iso/grafpy-boot
mkdir /abit/iso/ubuntu-boot
mkdir /abit/iso/pmagic-boot
mkdir /abit/iso/systemcd-boot

for 7 distros of Damn Small Linux, Slax, Mepis, Grafpuppy, Ubunu, Parted Magic and SystemrescueCD. Their version numbers are stated in the menu.lst below.

I use "-boot" for the folder names because some distros may have their own folders using the distro own names, for example slax and pmagic.

I wrote a script called mountiso to execute the two lines of commands

saikee@saikee-desktop:~$ cat /abit/saikee/Desktop/mountiso
umount /mnt/cdrom
mount -t iso9660 -o ro,loop=/dev/loop0 $1 /mnt/cdrom

This allows me to mount any iso file by bash command, say for iso slax-6.0.0-rc5.iso

/bin/bash mountiso slax-6.0.0-rc5.iso

The Slax iso when expanded shows two directories of /boot and /slax inside. I can then copy the expanded iso file in /mnt/cdrom into the folder I created in Step-1

cp -R /mnt/cdrom/* /abit/iso/slax-boot/

I have to repeat Step-2 for each iso file.

The folder /abit/iso will be eventually a DVD iso and so to make it bootable by Grub we must have

I was using an installed Ubuntu 7.04 to do the above work and so Ubuntu's /boot/grub has all the information I need. Therefore all I need to do is to copy the content of Ubuntu's /boot/grub directory into /abit/iso after creating the directories there first

mkdir /abit/iso/boot
mkdir /abit/iso/boot/grub
cp /boot/grub/* /abit/iso/boot/grub/

at this stage all the Grub files will be available as shown below

root@saikee-desktop:/home/saikee# ls /abit/iso/boot/grub
default        fat_stage1_5  menu.lst~          stage1           xfs_stage1_5
device.map     jfs_stage1_5  minix_stage1_5     stage2
e2fs_stage1_5  menu.lst      reiserfs_stage1_5  stage2_eltorito

This is by far the most difficult thing to explain. I shall only do it by example. Slax in the above is the perfect system for this type of illustration. The above information shows it has two directories of "/slax" and "/boot" so the first thing I have to do is to move the /slax directory from /abit/iso/slax-boot to /abit/iso, leaving only the /boot there for reference only. This is because when the DVD is booted the installer has been written to search only the root directory whereas the /boot directory is the one I can control by telling Grub where to find it. I can't put /boot in the root directory because many distros have /boot too.

I now show how to get the isolinux.cfg by repeating just the "ls" command going into deeper level each time.

root@saikee-desktop:/home/saikee# ls /abit/iso/slax-boot/
boot

root@saikee-desktop:/home/saikee# ls /abit/iso/slax-boot/boot
bootinst.bat  bootlilo.sh  dos        isolinux  syslinux      vmlinuz
bootinst.sh   chain.c32    initrd.gz  mt86p     vesamenu.c32

root@saikee-desktop:/home/saikee# ls /abit/iso/slax-boot/boot/isolinux
isolinux.bin  isolinux.boot  isolinux.cfg

root@saikee-desktop:/home/saikee# cat /abit/iso/slax-boot/boot/isolinux/isolinux.cfg
PROMPT 0
TIMEOUT 200
DEFAULT /boot/vesamenu.c32

LABEL xconf
MENU LABEL Slax Graphics mode (KDE)
KERNEL /boot/vmlinuz
APPEND vga=769 initrd=/boot/initrd.gz ramdisk_size=6666 root=/dev/ram0 rw autoexec=xconf;kdm

LABEL pchanges
MENU LABEL Slax Graphics mode with Persistent Changes
KERNEL /boot/vmlinuz
APPEND vga=769 initrd=/boot/initrd.gz ramdisk_size=6666 root=/dev/ram0 rw changes=/slax/slaxsave.dat autoexec=xconf;kdm

LABEL copy2ram
MENU LABEL Slax Graphics mode, Copy To RAM
KERNEL /boot/vmlinuz
APPEND vga=769 initrd=/boot/initrd.gz ramdisk_size=6666 root=/dev/ram0 rw copy2ram autoexec=xconf;kdm

LABEL startx
MENU LABEL Slax Graphics VESA mode (1024x768)
KERNEL /boot/vmlinuz
APPEND vga=769 initrd=/boot/initrd.gz ramdisk_size=6666 root=/dev/ram0 rw autoexec=kdm

LABEL slax
MENU LABEL Slax Text mode
KERNEL /boot/vmlinuz
APPEND vga=normal initrd=/boot/initrd.gz ramdisk_size=6666 root=/dev/ram0 rw

LABEL memtest86
MENU LABEL Run Memtest utility
KERNEL /boot/mt86p

root@saikee-desktop:/home/saikee#

The part of the isolinux.cfg that is of interest to me has only two lines I have highlighted in red

I now show the end result of the Grub menu, which must be stored as /abit/iso/boot/grub/menu.lst, and the red is the conversion.

root@saikee-desktop:/home/saikee# cat /abit/iso/boot/grub/menu.lst

title DSL 4.0
kernel /DSL-boot/boot/isolinux/linux24 ramdisk_size=100000 init=/etc/init lang=us apm=power-off vga=791 nomce noapic quiet BOOT_IMAGE=knoppix
initrd /DSL-boot/boot/isolinux/minirt24.gz

title Slax 6.0.0 rc5
kernel /slax-boot/boot/vmlinuz vga=769 ramdisk_size=6666 root=/dev/ram0 rw autoexec=xconf;kdm
initrd /slax-boot/boot/initrd.gz

title GrafPup 2.0
kernel /grafpup-boot/vmlinuz root=/dev/ram0 vga=0x312 loglevel=1 PMEDIA=idecd
initrd /grafpup-boot/initrd.gz

title Mepis 6.9.5
kernel /mepis-boot/boot/vmlinuz init=/etc/init vga=normal quiet drvr=vesa
initrd /mepis-boot/boot/initrd.gz

title SystemrescueCD 0.3.7 label fb1024
kernel /systemcd-boot/isolinux/rescuecd root=/dev/ram0 init=/linuxrc vga=791 looptype=squashfs loop=/sysrcd.dat dokeymap cdroot splash=silent splash=silent
initrd /systemcd-boot/isolinux/rescuecd.igz

title ubuntu 6.10 desktop safe ^graphics mode
kernel /casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper xforcevesa ramdisk_size=1048576 root=/dev/ram rw quiet splash --
initrd /casper/initrd.gz

title Parted Magic 1.8
kernel /pmagic-boot/isolinux/bzImage noapic root=/dev/ram0 init=/linuxrc ramdisk_size=100000 skip
initrd /pmagic-boot/isolinux/initrd.gz

You will see I have only changed "KERNEL" with "kernel" and correctly located the where about of the kernel "vmlinuz" to be found in directory /slax-boot/boot. Remember after you have brun the DVD iso the /abit/iso front end will disappear.

The isolinux specifies the ram disk file as a parameter of the KERNEL statement with "initrd=/boot/initrd.gz" forming part of the command structure. In Grub I have separated it into a proper "initrd" statement. That is all I needed to change an iso booting with isolinux to booting with Grub. I do not touch other parameters at all.

To summarize the step of converting an iso booting from isolinux to Grub the steps are

I could have just done two iso to make the thread shorter but decided to put 7 iso files in because there are 6 examples showing how isolinux can be converted to Grub. One of the 7 has Grub already and I have shown how we could modify it too to multi-boot. The isolinux information is left at the rear of the thread in case any reader may find more information useful.

This has to be the easiest thing in life for creating your own bootable DVD. Just follow the steps outlined in the Chapter 3.4 of Grub Manual. http://www.gnu.org/software/grub/manual/html_node/Making-a-GRUB-bootable-CD_002dROM.html#Making-a-GRUB-bootable-CD_002dROM

I wrote a script call makeiso just to do just that

root@saikee-desktop:/home/saikee# cat /abit/makeiso
mkisofs -R -b boot/grub/stage2_eltorito -no-emul-boot -boot-load-size 4 -boot-info-table -o grub.iso iso

I issue the makeiso command in directory /abit. The end product of the about command is a large iso file call grub.iso

To burn the grub.iso I just called up K3B and clicked the file name. The DVD, with 1.8 Gb from the 7 distros, was ready in 6 minutes. I used a re-writeable DVD.

Conclusion : I now have a DVD that boots 7 distros successfully.

The above information is also useful/sufficient for any user wanting to create his/her customized bootable CD/DVD

The following information are included just for the reference purpose only.

For completeness I enclose the relevant parts of the isolinux.cfg from the other distros below. The menu.lst I wrote is already given at the above.

DSL's isolinux.cfg is in /boot/isolinux directory. Its "KNOPPIX" directory should be available in the / directory

LABEL dsl
KERNEL linux24
APPEND ramdisk_size=100000 init=/etc/init lang=us apm=power-off vga=791 initrd=minirt24.gz nomce noapic quiet BOOT_IMAGE=knoppix

Grafpuppy isolinux.cfg is in / directory…..

Lastly the complete content of my /abit/iso (before turning into the iso), looks like this….

Last edited by saikee : 2007-08-07