How to create a custom Ubuntu live from scratch
This procedure shows how to create a bootable and installable Ubuntu Live (along with the automatic hardware detection and configuration) from scratch. The steps described below are also available in this repo in the /scripts directory.
Authors
    • Marcos Vallim - Founder, Author, Development, Test, Documentation - mvallim 
    • Ken Gilmer - Commiter, Development, Test, Documentation - kgilmer 
See also the list of contributors who participated in this project.
Ways of Using this Tutorial
    • (Recommended) follow the directions step by step below to understand how to build an Ubuntu ISO. 
    • Run the build.sh script in the scripts directory after checking this repo out locally. 
    • Fork this repo and run the github action build. This will generate an ISO in your github account. 
Terms
    • build system - the computer environment running the build scripts that generate the ISO. 
    • live system - the computer environment that runs from the live OS, generated by a build system. This may also be referred to as the chroot environment. 
    • target system - the computer environment that runs after installation has completed from a live system. 
Prerequisites (GNU/Linux Debian/Ubuntu)
Install packages we need in the build system required by our scripts.
sudo apt-get install \
    binutils \
    debootstrap \
    squashfs-tools \
    xorriso \
    grub-pc-bin \
    grub-efi-amd64-bin \
    mtools
mkdir $HOME/live-ubuntu-from-scratch
Bootstrap and Configure Ubuntu
debootstrap is a program for generating OS images. We install it into our build system to begin generating our ISO.
    • Checkout bootstrap
      sudo debootstrap \
         --arch=amd64 \
         --variant=minbase \
         focal \
         $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 (grub among them), these mount points are necessary inside the chroot environment, so we are able to finish the installation 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 system call or the chroot wrapper program. The modified environment is called a chroot jail.
Reference: https://en.wikipedia.org/wiki/Chroot
From this point we will be configuring the live system.
    1. Access chroot environment
       sudo chroot $HOME/live-ubuntu-from-scratch/chroot
    2. 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 are able to finish the installation without errors.
    3. Set a custom hostname
       echo "ubuntu-fs-live" > /etc/hostname
    4. Configure apt sources.list
       cat <<EOF > /etc/apt/sources.list
       deb http://us.archive.ubuntu.com/ubuntu/ focal main restricted universe multiverse
       deb-src http://us.archive.ubuntu.com/ubuntu/ focal main restricted universe multiverse
       deb http://us.archive.ubuntu.com/ubuntu/ focal-security main restricted universe multiverse
       deb-src http://us.archive.ubuntu.com/ubuntu/ focal-security main restricted universe multiverse
       deb http://us.archive.ubuntu.com/ubuntu/ focal-updates main restricted universe multiverse
       deb-src http://us.archive.ubuntu.com/ubuntu/ focal-updates main restricted universe multiverse
       EOF
    5. Update indexes packages
       apt-get update
    6. Install systemd
       apt-get install -y libterm-readline-gnu-perl 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.
    7. Configure machine-id and divert
       dbus-uuidgen > /etc/machine-id
       
       ln -fs /etc/machine-id /var/lib/dbus/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.
    8. Upgrade packages
       apt-get -y upgrade
    9. Install packages needed for Live System
       apt-get install -y \
           sudo \
           ubuntu-standard \
           casper \
           lupin-casper \
           discover \
           laptop-detect \
           os-prober \
           network-manager \
           resolvconf \
           net-tools \
           wireless-tools \
           wpagui \
           locales \
           grub-common \
           grub-gfxpayload-lists \
           grub-pc \
           grub-pc-bin \
           grub2-common
       apt-get install -y --no-install-recommends linux-generic
    10. Graphical installer
       apt-get install -y \
          ubiquity \
          ubiquity-casper \
          ubiquity-frontend-gtk \
          ubiquity-slideshow-ubuntu \
          ubiquity-ubuntu-artwork
       The next steps will appear, as a result of the packages that will be installed from the previous step, this will happen without anything having to be informed or executed.
        1. Configure keyboard 
        
        
        2. Console setup 
        
    11. Install window manager
       apt-get install -y \
           plymouth-theme-ubuntu-logo \
           ubuntu-gnome-desktop \
           ubuntu-gnome-wallpapers
    12. Install useful applications
       apt-get install -y \
           clamav-daemon \
           terminator \
           apt-transport-https \
           curl \
           vim \
           nano \
           less
    13. Install Visual Studio Code (optional)
    14. 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
    15. Then update the package cache and install the package using
       apt-get update
       
       apt-get install -y code
    16. Install Google Chrome (optional)
    17. 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
    18. Then update the package cache and install the package using
       apt-get update
       
       apt-get install google-chrome-stable
    19. Install Java JDK 8 (optional)
       apt-get install -y \
           openjdk-8-jdk \
           openjdk-8-jre
    20. Remove unused applications (optional)
       apt-get purge -y \
           transmission-gtk \
           transmission-common \
           gnome-mahjongg \
           gnome-mines \
           gnome-sudoku \
           aisleriot \
           hitori
    21. Remove unused packages
       apt-get autoremove -y
    22. Reconfigure packages
    23. Generate locales
       dpkg-reconfigure locales
        1. Select locales
            
        2. Select default locale
            
    24. Reconfigure resolvconf
       dpkg-reconfigure resolvconf
        1. Confirm changes
            
            
            
    25. Configure network-manager
       cat <<EOF > /etc/NetworkManager/NetworkManager.conf
       [main]
       rc-manager=resolvconf
       plugins=ifupdown,keyfile
       dns=dnsmasq
       
       [ifupdown]
       managed=false
       EOF
    26. Reconfigure network-manager
       dpkg-reconfigure network-manager
    27. Cleanup the chroot environment
    28. If you installed software, be sure to run
       truncate -s 0 /etc/machine-id
    29. Remove the diversion
       rm /sbin/initctl
       
       dpkg-divert --rename --remove /sbin/initctl
    30. 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
We are now back in our build environment after setting up our live system and will continue creating files necessary to generate the ISO.
    1. Access build directory
       cd $HOME/live-ubuntu-from-scratch
    2. Create directories
       mkdir -p image/{casper,isolinux,install}
    3. Copy kernel images
       sudo cp chroot/boot/vmlinuz-**-**-generic image/casper/vmlinuz
       
       sudo cp chroot/boot/initrd.img-**-**-generic image/casper/initrd
    4. Copy memtest86+ binary (BIOS)
       sudo cp chroot/boot/memtest86+.bin image/install/memtest86+
    5. Download and extract memtest86 binary (UEFI)
       wget --progress=dot https://www.memtest86.com/downloads/memtest86-usb.zip -O image/install/memtest86-usb.zip
       
       unzip -p image/install/memtest86-usb.zip memtest86-usb.img > image/install/memtest86
       
       rm -f image/install/memtest86-usb.zip

GRUB menu configuration
    1. Access build directory
       cd $HOME/live-ubuntu-from-scratch
    2. Create base point access file for grub
       touch image/ubuntu
    3. 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 FS without installing" {
          linux /casper/vmlinuz boot=casper nopersistent toram quiet splash ---
          initrd /casper/initrd
       }
       
       menuentry "Install Ubuntu FS" {
          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 Memtest86+ (BIOS)" {
          linux16 /install/memtest86+
       }
       
       menuentry "Test memory Memtest86 (UEFI, long load time)" {
          insmod part_gpt
          insmod search_fs_uuid
          insmod chain
          loopback loop /install/memtest86
          chainloader (loop,gpt1)/efi/boot/BOOTX64.efi
       }
       EOF

Create manifest
Next we create a file filesystem.manifest to specify each package and it's version that is installed on the live system. We create another file filesystem.manifest-desktop which specifies which files will be installed on the target system. Once the Ubiquity installer completes, it will remove packages specified in filesystem.manifest that are not listed in filesystem.manifest-desktop.
    1. Access build directory
       cd $HOME/live-ubuntu-from-scratch
    2. Generate manifest
       sudo chroot chroot dpkg-query -W --showformat='${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
After everything has been installed and preconfigured in the chrooted environment, we need to generate an image of everything that was done by following the next steps in the build environment.
    1. Access build directory
       cd $HOME/live-ubuntu-from-scratch
    2. Create squashfs
       sudo mksquashfs chroot image/casper/filesystem.squashfs
       Squashfs is a highly compressed read-only filesystem for Linux. It uses zlib compression to compress both files, inodes and directories. Inodes in the system are very small and all blocks are packed to minimize data overhead. Block sizes greater than 4K are supported up to a maximum of 64K. Squashfs is intended for general read-only filesystem use, for archival use (i.e. in cases where a .tar.gz file may be used), and in constrained block device/memory systems (e.g. embedded systems) where low overhead is needed.
    3. Write the filesystem.size
       printf $(sudo du -sx --block-size=1 chroot | cut -f1) > image/casper/filesystem.size

Create diskdefines
README file often found on Linux LiveCD installer discs, such as an Ubuntu Linux installation CD; typically named “README.diskdefines” and may be referenced during installation.
    1. Access build directory
       cd $HOME/live-ubuntu-from-scratch
    2. 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

Create ISO Image for a LiveCD (BIOS + UEFI)
    1. Access image directory
       cd $HOME/live-ubuntu-from-scratch/image
    2. Create a grub UEFI image
       grub-mkstandalone \
          --format=x86_64-efi \
          --output=isolinux/bootx64.efi \
          --locales="" \
          --fonts="" \
          "boot/grub/grub.cfg=isolinux/grub.cfg"
    3. 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 && \
          LC_CTYPE=C mmd -i efiboot.img efi efi/boot && \
          LC_CTYPE=C mcopy -i efiboot.img ./bootx64.efi ::efi/boot/
       )
    4. Create a grub BIOS image
       grub-mkstandalone \
          --format=i386-pc \
          --output=isolinux/core.img \
          --install-modules="linux16 linux normal iso9660 biosdisk memdisk search tar ls" \
          --modules="linux16 linux normal iso9660 biosdisk search" \
          --locales="" \
          --fonts="" \
          "boot/grub/grub.cfg=isolinux/grub.cfg"
    5. Combine a bootable Grub cdboot.img
       cat /usr/lib/grub/i386-pc/cdboot.img isolinux/core.img > isolinux/bios.img
    6. Generate md5sum.txt
       sudo /bin/bash -c "(find . -type f -print0 | xargs -0 md5sum | grep -v -e 'md5sum.txt' -e 'bios.img' -e 'efiboot.img' > md5sum.txt)"
    7. Create iso from the image directory using the command-line
       sudo xorriso \
          -as mkisofs \
          -iso-level 3 \
          -full-iso9660-filenames \
          -volid "Ubuntu from scratch" \
          -output "../ubuntu-from-scratch.iso" \
          -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 \
          -m "isolinux/efiboot.img" \
          -m "isolinux/bios.img" \
          -graft-points \
             "/EFI/efiboot.img=isolinux/efiboot.img" \
             "/boot/grub/bios.img=isolinux/bios.img" \
             "."

Alternative way, if previous one fails, create an Hybrid ISO
    1. Create a ISOLINUX (syslinux) boot menu
       cat <<EOF> isolinux/isolinux.cfg
       UI vesamenu.c32
       
       MENU TITLE Boot Menu
       DEFAULT linux
       TIMEOUT 600
       MENU RESOLUTION 640 480
       MENU COLOR border       30;44   #40ffffff #a0000000 std
       MENU COLOR title        1;36;44 #9033ccff #a0000000 std
       MENU COLOR sel          7;37;40 #e0ffffff #20ffffff all
       MENU COLOR unsel        37;44   #50ffffff #a0000000 std
       MENU COLOR help         37;40   #c0ffffff #a0000000 std
       MENU COLOR timeout_msg  37;40   #80ffffff #00000000 std
       MENU COLOR timeout      1;37;40 #c0ffffff #00000000 std
       MENU COLOR msg07        37;40   #90ffffff #a0000000 std
       MENU COLOR tabmsg       31;40   #30ffffff #00000000 std
       
       LABEL linux
        MENU LABEL Try Ubuntu FS
        MENU DEFAULT
        KERNEL /casper/vmlinuz
        APPEND initrd=/casper/initrd boot=casper
       
       LABEL linux
        MENU LABEL Try Ubuntu FS (nomodeset)
        MENU DEFAULT
        KERNEL /casper/vmlinuz
        APPEND initrd=/casper/initrd boot=casper nomodeset
       EOF
    2. Include syslinux bios modules
       apt install -y syslinux-common && \
       cp /usr/lib/ISOLINUX/isolinux.bin isolinux/ && \
       cp /usr/lib/syslinux/modules/bios/* isolinux/
    3. Create iso from the image directory
       sudo xorriso \
          -as mkisofs \
          -iso-level 3 \
          -full-iso9660-filenames \
          -volid "Ubuntu from scratch" \
          -output "../ubuntu-from-scratch.iso" \
        -isohybrid-mbr /usr/lib/ISOLINUX/isohdpfx.bin \
        -eltorito-boot \
            isolinux/isolinux.bin \
            -no-emul-boot \
            -boot-load-size 4 \
            -boot-info-table \
            --eltorito-catalog isolinux/isolinux.cat \
        -eltorito-alt-boot \
            -e /EFI/boot/efiboot.img \
            -no-emul-boot \
            -isohybrid-gpt-basdat \
        -append_partition 2 0xef EFI/boot/efiboot.img \
          "$HOME/live-ubuntu-from-scratch/image"
Make a bootable USB image
It is simple and easy, using "dd"
sudo dd if=ubuntu-from-scratch.iso of=<device> status=progress oflag=sync
Summary
This completes the process of creating a live Ubuntu installer from scratch. The generated ISO may be tested in a virtual machine such as VirtualBox or written to media and booted from a standard PC.
Contributing
Please read CONTRIBUTING.md for details on our code of conduct, and the process for submitting pull requests to us.
Versioning
We use GitHub for versioning. For the versions available, see the tags on this repository.
License
This project is licensed under the GNU GENERAL PUBLIC LICENSE - see the LICENSE file for details


A partir de ceci, je voudrais realiser ma propre distribution avec les logiciels suivant: R, Rstudio, Jupyterlab, Ugene, ImageJ, VLC, biopython, zotero, libreoffice, firefox et peut etre d'autres logiciels par la suite.