How To Make CustomRescueCD

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Overview

This document will walk readers through the steps to create a Gentoo stage4 inside a squashfs and subsequently use it in a bootable ISO9660 image.

The steps are to make a Gentoo Install inside a directory. This follows the Handbook. Add or remove packages to your taste. This will become customrescuecd-squash, which will be the root filesystem in the CD.

This will then be packaged with a syslinux /boot to make the bootable ISO9660 image.

Burning the image to a CD or making a bootable USB stick will not be addressed.

Examine the structure of the ISO:

  • ./boot/grub/font.pf2
  • ./boot/grub/grub.cfg <-- Grub Configuration File for EFI BOOT
  • ./boot/grub/x86_64-efi
  • ./boot/grub/x86_64-efi/all_video.mod
  • ./boot/grub/x86_64-efi/efi_gop.mod
  • ./boot/grub/x86_64-efi/efi_uga.mod
  • ./boot/grub/x86_64-efi/gfxterm.mod
  • ./boot/grub/x86_64-efi/video.mod
  • ./boot/grub/x86_64-efi/videoinfo.mod
  • ./boot/grub/x86_64-efi/videotest.mod
  • ./boot/memtest86plus/memtest
  • ./boot/memtest86plus/memtest.bin <-- Memtest kernel for bios boot
  • ./boot/syslinux/chain.c32
  • ./boot/syslinux/syslinux.cfg <--- Main Syslinux Configuration File
  • ./boot/syslinux/customresccd.cfg
  • ./boot/syslinux/customresccd_head.cfg
  • ./boot/syslinux/customresccd_pxe.cfg
  • ./boot/syslinux/customresccd_sys.cfg
  • ./boot/syslinux/customresccd_tail.cfg
  • ./boot/syslinux/isohdpfx.bin <--- Syslinux MBR for Bios Boot
  • ./boot/syslinux/isolinux.bin <--- Syslinux Image
  • ./boot/syslinux/boot.cat <--- Syslinux Boot Catalogue
  • ./boot/syslinux/ldlinux.c32
  • ./boot/syslinux/ldlinux.sys
  • ./boot/syslinux/libcom32.c32
  • ./boot/syslinux/libutil.c32
  • ./boot/syslinux/memdisk
  • ./boot/syslinux/poweroff.c32
  • ./boot/syslinux/pxelinux.0
  • ./boot/syslinux/reboot.c32
  • ./boot/syslinux/vesamenu.c32
  • ./boot/syslinux/whichsys.c32
  • ./boot/x86_64/customrescue64 <-- CustomRescueCd KERNEL
  • ./customresccd/x86_64/customrescuecd.sfs <--- SquashFS
  • ./customresccd/x86_64/customrescuecd.sha512 <---- Sha512 of Squashfs
  • ./EFI/boot/bootx64.efi < ---- Grub Efi Executable for usb stick boot
  • ./EFI/customiso/grub.img <--- Grub Partition in append to iso for efi boot that contain .efi executable

Create The Work Space

I advise you to keep two terminals open, one for the stage 4 chroot and another you will need to create the squash and the iso ahead.

/mnt/customrescuecd-squash is for the stage4. This will be turned into a squashfs later.

/mnt/customrescuecd64 is for the files that will become the ISO9660 filesystem, including the squashfs above.

root #mkdir /mnt/customrescuecd-squash /mnt/customrescuecd64 /mnt/customrescuecd64/boot

Download a Gentoo Stage 3, unpack it to /mnt/customrescuecd-squash, and chroot into it and build the system following the Gentoo Handbook and other guides as necessary.

Install necessary tools to the system:

root #emerge -1avn syslinux grub genkernel gentoo-sources

Build kernel

Use genkernel to make a kernel and initramfs, add extra parameters as necessary (see Genkernel for details):

root #genkernel --bootdir=/mnt/customrescuecd64/boot --firmware all

The customrescuecd64 directory must contain these subdirectories:

  • boot/syslinux
  • boot/grub/x86_64-efi
  • boot/memtest86plus
  • boot/x86_64
  • EFI/boot
  • EFI/customiso
  • customresccd/x86_64

Creating the squashfs

Make an excludes file with the following content.

FILE exclude.txt
proc/*
sys/*
dev/*
run/*
boot/*
root/*
var/cache/edb/*
var/db/pkg/*
var/db/repos/gentoo/*
var/db/repos/local/*
var/db/repos/palemoon/*
var/tmp/portage/*
var/cache/distfiles/*
var/cache/binpkgs/*
var/log/*
var/tmp/*
usr/include/*
usr/src/*
etc/kernels/*
etc/portage/*

Add any other files and directories to be excluded from the squashfs

Build the squashfs using the exclude.txt file created above:

root #mksquashfs /mnt/customresccd-squash/ /mnt/customrescuecd64/customresccd/x86_64/customrescuecd.sfs -wildcards -ef exclude.txt -b 1024K -comp xz -progress -processors 4 -Xdict-size 100%

Bootloader

Syslinux

Download the syslinux cfg from syslinux.cfg.tar.xz and explode into customrescuecd64/boot/syslinux/ the content of this directory must be the one that follow! All *.c32 and memdisk isolinux.bin boot.cat pxelinux.0 isohdpfx.bin file you can copy from your stage4 at folder /usr/share/syslinux/

  • customresccd_tail.cfg
  • poweroff.c32
  • customresccd_head.cfg
  • boot.cat
  • syslinux.cfg
  • pxelinux.0
  • reboot.c32
  • isohdpfx.bin
  • libcom32.c32
  • whichsys.c32
  • chain.c32
  • ldlinux.sys
  • memdisk
  • vesamenu.c32
  • isolinux.bin
  • customresccd_pxe.cfg
  • ldlinux.c32
  • customresccd_sys.cfg
  • customresccd.cfg
  • libutil.c32

Grub

in the directory customrescuecd64/boot/grub/x86_64-efi/ copy the files all_video.mod efi_gop.mod efi_uga.mod gfxterm.mod videoinfo.mod videotest.mod from /usr/lib/grub/x86_64-efi/ of your stage4

download the font.pf2 in the directory customrescuecd64/boot/grub/

Create the file /mnt/customrescuecd64/boot/grub/grub.cfg adjusting kernel and initramfs versions as necessary:

FILE /mnt/customrescuecd64/boot/grub/grub.cfg
set timeout=90
set default=0
set fallback=1
set pager=1

if loadfont /boot/grub/font.pf2 ; then
	set gfxmode=auto
	insmod efi_gop
	insmod efi_uga
	insmod gfxterm
	insmod all_video
	insmod videotest
	insmod videoinfo
	terminal_output gfxterm
fi

menuentry "Boot CustomRescueCd" {
	set gfxpayload=keep
	linux /boot/vmlinuz-5.7.2-gentoo loop=/customresccd/x86_64/customrescuecd.sfs looptype=squashfs
	initrd /boot/initramfs-5.7.2-gentoo
}

cd into customrescuecd64/EFI/customiso/

create a empty file named grub.img to create the boot efi partition

root #dd if=/dev/zero of=grub.img bs=1M count=2

format it with FAT12 filesystem

root # mkfs.vfat -f 1 -F 12 grub.img

mount grub.img into /boot/efi of your stage4

root # mount -t vfat grub.img customrescuecd-squash/boot/efi/

from your stage4 chroot

root # mkdir -p /boot/efi/efi/boot
root # cd /boot/efi/efi/boot

create the grub image efi boot executable

root # grub-mkimage -o bootx64.efi -O x86_64-efi -p /boot/grub boot linux linux16 normal configfile part_gpt part_msdos fat iso9660 udf test keystatus loopback regexp probe efi_gop efi_uga all_video gfxterm font echo read help ls cat halt reboot
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