create_image

#!/bin/bash

export IMAGE_NAME="lfs.iso"
export ISO_DIR="$LFS"/iso

[ -z "$INITRAMFSNAME" ] && INITRAMFSNAME=initramfs-lfs-x86.cpio.gz

build_initramfs()
{
    echo "Building initramfs..."
    [ -f "$LFS"/boot/initramfs-lfs-x86.cpio.gz ] && rm "$LFS"/boot/initramfs-lfs-x86.cpio.gz

    if [ ! -f "$LFS"/boot/vmlinuz ]; then
        echo "Kernel was not build.. not creating initramfs"
        exit 1
    fi

    cd "$LFS"
    cat > init <<EOM
#!/bin/sh

mount -t proc none /proc
mount -t sysfs none /sys

echo -e "\nBoot took \$(cut -d' ' -f1 /proc/uptime) seconds\n"

exec /bin/sh
EOM
    "$LFS"/bin/chmod +x init

    "$LFS"/usr/bin/find init bin dev etc lib lib64 mnt opt proc   \
        root run sbin sys usr var                               \
        | "$LFS"/bin/cpio -H newc -o                              \
        | "$LFS"/bin/gzip -9 > "$LFS"/boot/"$INITRAMFSNAME"
    echo "Building initramfs complete"
}


build_iso()
{
    {
    if [ -f "$ISO_DIR"/"$IMAGE_NAME" ]; then
        echo "iso image already present.. $ISO_DIR/$IMAGE_NAME .. exiting"
        exit 0
    fi

    [ -d "$ISO_DIR" ] && rm -rf "$ISO_DIR"

    # Create staging area
    mkdir -p "$ISO_DIR"
    mkdir -p "$ISO_DIR"/rootpath
    mkdir -p "$ISO_DIR"/rootpath/boot/grub/i386-pc/

    # Copy the kernel and initramfs file to staging area
    cp "$LFS"/boot/* "$ISO_DIR"/rootpath/boot/

    # Copy all the grub utilities to staging area
    cp -Lrp "$LFS"/usr/lib/grub/i386-pc/* "$ISO_DIR"/rootpath/boot/grub/i386-pc/

    # Simple grub.cfg file
    cat > "$ISO_DIR"/rootpath/boot/grub/grub.cfg <<EOF
    set default=0
    set timeout=1

    menuentry 'Linux From Scratch - Gowda' {
        echo "Loading kernel"
        linux /boot/vmlinuz root=/dev/ram0 nmi_watchdog=1 console=tty0 console=ttyS0,115200
        echo "Loading initrd"
        initrd /boot/initramfs-lfs-x86.cpio.gz
    }
EOF

    # Create a sparse file of 512MB size
    truncate -s 256M "$ISO_DIR"/root.part

    # Create a ext3 file system
    "$LFS"/sbin/mke2fs -t ext3 -b 4096 -m 0 -j -F "$ISO_DIR"/root.part

    # Copy/Populate the file from staging area
    DEBUGFS=$LFS/sbin/debugfs               \
        "$LFS"/usr/sbin/populate-extfs.sh   \
        "$ISO_DIR"/rootpath                 \
        "$ISO_DIR"/root.part

    # Create a GRUB image
    "$LFS"/usr/bin/grub-mkimage                     \
        -O i386-pc                                  \
        -p '(hd0,msdos1)/boot/grub'                 \
        -d "$ISO_DIR"/rootpath/boot/grub/i386-pc    \
        -o "$ISO_DIR"/core.img                      \
        biosdisk ext2 part_msdos part_gpt

    # Create another final image/iso 
    truncate -s 512M "$ISO_DIR"/"$IMAGE_NAME"

    # Partition the disk and make it bootable
    sed -e 's/\s*\([\+0-9a-zA-Z]*\).*/\1/' <<EOF | fdisk "$ISO_DIR"/"$IMAGE_NAME"
o # clear the in memory partition table
n # new partition
p # primary partition
1 # partition number 1
  # default - start at beginning of disk
  # Take all the space
a # select the bootable partition
w # write the partition table
EOF

    # We could have made use of dd utility but kpratx is better
    kpartx -av "$ISO_DIR"/"$IMAGE_NAME"
    sleep 1
    dd if="$ISO_DIR"/root.part of=/dev/mapper/loop0p1 bs=4096 conv=sparse
    kpartx -dv "$ISO_DIR"/"$IMAGE_NAME"
    sleep 1
    } >/dev/null 2>&1
}

write_grub()
{

python2.7 <<EOF

import os
import sys

lfs_env = os.environ['LFS']
iso_dir = os.environ['ISO_DIR']
img_name_env = os.environ['IMAGE_NAME']
disk_img = iso_dir + "/" + img_name_env

grub_boot = iso_dir + "/rootpath/boot/grub/i386-pc/boot.img"
grub_core = iso_dir + "/core.img"

boot = file(grub_boot, "rb").read()
core = file(grub_core, "rb").read()
fd = os.open(disk_img, os.O_WRONLY)

os.lseek(fd, 0, os.SEEK_SET)
os.write(fd, boot[:446])
os.lseek(fd, 512, os.SEEK_SET)
os.write(fd, core)

os.close(fd)
EOF
    
}

clean_up()
{
    rm -rf "$ISO_DIR"/core.img "$ISO_DIR"/root.part "$ISO_DIR"/rootpath    
    unset IMAGE_NAME ISO_DIR
}

build_initramfs
build_iso
write_grub

echo "*****************************************"
echo "Your iso image is ready - $ISO_DIR/$IMAGE_NAME"
echo "*****************************************"
clean_up