sudo sed -i '/^ui / d' /tmp/custom/newiso/isolinux/isolinux.cfg   # disable gfxboot
sudo sed -i 's/quiet splash/quiet splash persistent/' /tmp/custom/newiso/isolinux/txt.cfg /tmp/custom/newiso/boot/grub/grub.cfg

# make persistent usb
sudo sfdisk /dev/sdb <<EOF
/dev/sdb1 : start=        2048, size=     6291456, type=b, bootable
/dev/sdb2 : start=     6293504, size=     8857664, type=83
EOF

sudo mkfs.vfat /dev/sdb1
sudo mkfs.ext4 -L casper-rw -O ^has_journal /dev/sdb2

sudo mount /dev/sdb1 /mnt
sudo mv /tmp/custom/newiso/isolinux /tmp/custom/newiso/syslinux
sudo mv /tmp/custom/newiso/syslinux/isolinux.cfg /tmp/custom/newiso/syslinux/syslinux.cfg

sudo rsync -av /tmp/custom/newiso/ /mnt
sudo syslinux -d syslinux /dev/sdb1

(cd /tmp/custom/newiso && find . -type f -print0 | xargs -0 md5sum | grep -v "\./md5sum.txt" ) | sudo tee /tmp/custom/newiso/md5sum.txt

sudo umount /mnt
sudo dd if=/usr/lib/syslinux/bios/mbr.bin of=/dev/sdb