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How to create a custom Ubuntu live from scratch

This procedure works and can create a bootable and installable Ubuntu Live (along with the automatic hardware detection and configuration) from scratch.

Prerequisites (GNU/Linux Debian/Ubuntu)

Install applications we need to build the environment.

sudo apt-get install \
    debootstrap \
    squashfs-tools \
    xorriso \
    grub-pc-bin \
    grub-efi-amd64-bin \
    mtools

mkdir $HOME/live-ubuntu-from-scratch

Bootstrap and Configure Ubuntu

Checkout bootstrap
```
sudo debootstrap \
   --arch=amd64 \
   --variant=minbase \
   bionic \
   $HOME/live-ubuntu-from-scratch/chroot \
   http://us.archive.ubuntu.com/ubuntu/
```
debootstrap is used to create a Debian base system from scratch, without requiring the availability of dpkg or apt. It does this by downloading .deb files from a mirror site, and carefully unpacking them into a directory which can eventually be chrooted into.
Configure external mount points
```
sudo mount --bind /dev $HOME/live-ubuntu-from-scratch/chroot/dev

sudo mount --bind /run $HOME/live-ubuntu-from-scratch/chroot/run
```
As we will be updating and installing packages (among them grub), these mount points are necessary inside the chroot environment, so we can be able to finish the installations without errors.

Define chroot environment

A chroot on Unix operating systems is an operation that changes the apparent root directory for the current running process and its children. A program that is run in such a modified environment cannot name (and therefore normally cannot access) files outside the designated directory tree. The term "chroot" may refer to the chroot(2) system call or the chroot(8) wrapper program. The modified environment is called a chroot jail.

Reference: https://en.wikipedia.org/wiki/Chroot

Access chroot environment

sudo chroot $HOME/live-ubuntu-from-scratch/chroot

Configure mount points, home and locale
```
mount none -t proc /proc

mount none -t sysfs /sys

mount none -t devpts /dev/pts

export HOME=/root

export LC_ALL=C
```
These mount points are necessary inside the chroot environment, so we can be able to finish the installations without errors.
Set a custom hostname
```
echo "ubuntu-live" > /etc/hostname
```

Configure apt sources.list

cat <<EOF > /etc/apt/sources.list
deb http://us.archive.ubuntu.com/ubuntu/ bionic main restricted universe multiverse 
deb-src http://us.archive.ubuntu.com/ubuntu/ bionic main restricted universe multiverse 

deb http://us.archive.ubuntu.com/ubuntu/ bionic-security main restricted universe multiverse 
deb-src http://us.archive.ubuntu.com/ubuntu/ bionic-security main restricted universe multiverse 

deb http://us.archive.ubuntu.com/ubuntu/ bionic-updates main restricted universe multiverse 
deb-src http://us.archive.ubuntu.com/ubuntu/ bionic-updates main restricted universe multiverse    
EOF

Update indexes packages
```
apt-get update
```
Install systemd
```
apt-get install -y systemd-sysv
```
systemd is a system and service manager for Linux. It provides aggressive parallelization capabilities, uses socket and D-Bus activation for starting services, offers on-demand starting of daemons, keeps track of processes using Linux control groups, maintains mount and automount points and implements an elaborate transactional dependency-based service control logic.
Configure machine-id and divert
```
dbus-uuidgen > /var/lib/dbus/machine-id

ln -fs /var/lib/dbus/machine-id /etc/machine-id
```
The /etc/machine-id file contains the unique machine ID of the local system that is set during installation or boot. The machine ID is a single newline-terminated, hexadecimal, 32-character, lowercase ID. When decoded from hexadecimal, this corresponds to a 16-byte/128-bit value. This ID may not be all zeros.
```
dpkg-divert --local --rename --add /sbin/initctl

ln -s /bin/true /sbin/initctl
```
dpkg-divert is the utility used to set up and update the list of diversions.

Install packages needed for Live System

apt-get install -y \
    ubuntu-standard \
    casper \
    lupin-casper \
    discover \
    laptop-detect \
    os-prober \
    network-manager \
    resolvconf \
    net-tools \
    wireless-tools \
    wpagui \
    locales \
    linux-generic

Configure grub

Graphical installer

apt-get install -y \
    ubiquity \
    ubiquity-casper \
    ubiquity-frontend-gtk \
    ubiquity-slideshow-ubuntu \
    ubiquity-ubuntu-artwork

Configure keyboard
Console setup

Install window manager

apt-get install -y \
    plymouth-theme-ubuntu-logo \
    ubuntu-gnome-desktop \
    ubuntu-gnome-wallpapers

Install useful applications

apt-get install -y \
    clamav-daemon \
    terminator \
    apt-transport-https \
    curl \
    vim \
    nano

Install Visual Studio Code

Download and install the key

curl https://packages.microsoft.com/keys/microsoft.asc | gpg --dearmor > microsoft.gpg

install -o root -g root -m 644 microsoft.gpg /etc/apt/trusted.gpg.d/

echo "deb [arch=amd64] https://packages.microsoft.com/repos/vscode stable main" > /etc/apt/sources.list.d/vscode.list

rm microsoft.gpg

Then update the package cache and install the package using
```
apt-get update

apt-get install -y code
```

Install Google Chrome

Download and install the key

wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add -

echo "deb http://dl.google.com/linux/chrome/deb/ stable main" > /etc/apt/sources.list.d/google-chrome.list

Then update the package cache and install the package using
```
apt-get update

apt-get install google-chrome-stable
```

Install Java JDK 8

apt-get install -y \
    openjdk-8-jdk \
    openjdk-8-jre

Remove unused applications

apt-get purge -y \
    transmission-gtk \
    transmission-common \
    gnome-mahjongg \
    gnome-mines \
    gnome-sudoku \
    aisleriot \
    hitori

Remove unused packages
```
apt-get autoremove -y
```

Reconfigure packages

Generate locales
```
dpkg-reconfigure locales
```
1. Select locales
2. Select default locale
Reconfigure resolvconf
```
dpkg-reconfigure resolvconf
```
1. Confirm changes

Configure network-manager

cat <<EOF > /etc/NetworkManager/NetworkManager.conf
[main]
rc-manager=resolvconf
plugins=ifupdown,keyfile
dns=dnsmasq

[ifupdown]
managed=false
EOF

Reconfigure network-manager
```
dpkg-reconfigure network-manager
```

Cleanup the chroot environment

If you installed software, be sure to run
```
rm /var/lib/dbus/machine-id
```

Remove the diversion

rm /sbin/initctl

dpkg-divert --rename --remove /sbin/initctl

Clean up

apt-get clean

rm -rf /tmp/* ~/.bash_history

umount /proc

umount /sys

umount /dev/pts

export HISTSIZE=0

exit

Unbind mount points

sudo umount $HOME/live-ubuntu-from-scratch/chroot/dev

sudo umount $HOME/live-ubuntu-from-scratch/chroot/run

Create the CD image directory and populate it

Access build directory
```
cd $HOME/live-ubuntu-from-scratch
```

Create directories

mkdir -p image/{casper,isolinux,install}

Copy kernel images

sudo cp chroot/boot/vmlinuz-**-**-generic image/casper/vmlinuz

sudo cp chroot/boot/initrd.img-**-**-generic image/casper/initrd

Copy memtest binary

sudo cp chroot/boot/memtest86+.bin image/install/memtest

Grub configuration

Access build directory
```
cd $HOME/live-ubuntu-from-scratch
```

Create image/isolinux/grub.cfg

cat <<EOF > image/isolinux/grub.cfg

search --set=root --file /ubuntu

insmod all_video

set default="0"
set timeout=30

menuentry "Try Ubuntu without installing" {
   linux /casper/vmlinuz boot=casper quiet splash ---
   initrd /casper/initrd
}

menuentry "Install Ubuntu" {
   linux /casper/vmlinuz boot=casper only-ubiquity quiet splash ---
   initrd /casper/initrd
}

menuentry "Check disc for defects" {
   linux /casper/vmlinuz boot=casper integrity-check quiet splash ---
   initrd /casper/initrd
}

menuentry "Test memory" {
   linux /install/memtest
}
EOF

Create manifest

Access build directory
```
cd $HOME/live-ubuntu-from-scratch
```

Generate manifest

sudo chroot chroot dpkg-query -W --showformat='${Package} ${Version}\n' | sudo tee image/casper/filesystem.manifest

sudo cp -v image/casper/filesystem.manifest image/casper/filesystem.manifest-desktop

sudo sed -i '/ubiquity/d' image/casper/filesystem.manifest-desktop

sudo sed -i '/casper/d' image/casper/filesystem.manifest-desktop

sudo sed -i '/discover/d' image/casper/filesystem.manifest-desktop

sudo sed -i '/laptop-detect/d' image/casper/filesystem.manifest-desktop

sudo sed -i '/os-prober/d' image/casper/filesystem.manifest-desktop

Compress the chroot

Access build directory
```
cd $HOME/live-ubuntu-from-scratch
```

Create squashfs

sudo mksquashfs chroot image/casper/filesystem.squashfs

Write the filesystem.size

printf $(sudo du -sx --block-size=1 chroot | cut -f1) > image/casper/filesystem.size

Create diskdefines

Access build directory
```
cd $HOME/live-ubuntu-from-scratch
```

Create file image/README.diskdefines

cat <<EOF > image/README.diskdefines
#define DISKNAME  Ubuntu from scratch
#define TYPE  binary
#define TYPEbinary  1
#define ARCH  amd64
#define ARCHamd64  1
#define DISKNUM  1
#define DISKNUM1  1
#define TOTALNUM  0
#define TOTALNUM0  1
EOF

Recognition as an Ubuntu from scratch

Access build directory
```
cd $HOME/live-ubuntu-from-scratch
```
Create an empty file named "ubuntu" and a hidden ".disk" folder.
```
touch image/ubuntu

mkdir image/.disk
```

Create ISO Image for a LiveCD (BIOS + UEFI)

Access image directory

cd $HOME/live-ubuntu-from-scratch/image

Create a grub UEFI image

grub-mkstandalone \
   --format=x86_64-efi \
   --output=isolinux/bootx64.efi \
   --locales="" \
   --fonts="" \
   "boot/grub/grub.cfg=isolinux/grub.cfg"

Create a FAT16 UEFI boot disk image containing the EFI bootloader

(
   cd isolinux && \
   dd if=/dev/zero of=efiboot.img bs=1M count=10 && \
   sudo mkfs.vfat efiboot.img && \
   mmd -i efiboot.img efi efi/boot && \
   mcopy -i efiboot.img ./bootx64.efi ::efi/boot/
)

Create a grub BIOS image

grub-mkstandalone \
   --format=i386-pc \
   --output=isolinux/core.img \
   --install-modules="linux normal iso9660 biosdisk memdisk search tar ls" \
   --modules="linux normal iso9660 biosdisk search" \
   --locales="" \
   --fonts="" \
   "boot/grub/grub.cfg=isolinux/grub.cfg"

Combine a bootable Grub cdboot.img

cat /usr/lib/grub/i386-pc/cdboot.img isolinux/core.img > isolinux/bios.img

Generate sha256sum.txt

sudo /bin/bash -c "(find . -type f -print0 | xargs -0 sha256sum | grep -v "\./sha256sum.txt" > sha256sum.txt)"

Create iso from the image directory using the command-line

sudo xorriso \
   -as mkisofs \
   -iso-level 3 \
   -full-iso9660-filenames \
   -volid "Ubuntu from scratch" \
   -eltorito-boot \
      boot/grub/bios.img \
      -no-emul-boot \
      -boot-load-size 4 \
      -boot-info-table \
      --eltorito-catalog boot/grub/boot.cat \
   --grub2-boot-info \
   --grub2-mbr /usr/lib/grub/i386-pc/boot_hybrid.img \
   -eltorito-alt-boot \
      -e EFI/efiboot.img \
      -no-emul-boot \
   -append_partition 2 0xef isolinux/efiboot.img \
   -output "../ubuntu-from-scratch.iso" \
   -graft-points \
      "." \
      /boot/grub/bios.img=isolinux/bios.img \
      /EFI/efiboot.img=isolinux/efiboot.img

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