654 lines
16 KiB
Markdown
654 lines
16 KiB
Markdown
# How to create a custom Ubuntu live from scratch
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<p align="center">
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<img src="images/live-boot.png">
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</p>
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This procedure shows how to create a **bootable** and **installable** Ubuntu Live (along with the automatic hardware detection and configuration) from scratch.
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## Prerequisites (GNU/Linux Debian/Ubuntu)
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Install applications we need to build the environment.
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```shell
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sudo apt-get install \
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binutils \
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debootstrap \
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squashfs-tools \
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xorriso \
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grub-pc-bin \
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grub-efi-amd64-bin \
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mtools
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```
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```shell
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mkdir $HOME/live-ubuntu-from-scratch
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```
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## Bootstrap and Configure Ubuntu
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* Checkout bootstrap
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```shell
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sudo debootstrap \
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--arch=amd64 \
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--variant=minbase \
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focal \
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$HOME/live-ubuntu-from-scratch/chroot \
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http://us.archive.ubuntu.com/ubuntu/
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```
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> **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.
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* Configure external mount points
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```shell
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sudo mount --bind /dev $HOME/live-ubuntu-from-scratch/chroot/dev
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sudo mount --bind /run $HOME/live-ubuntu-from-scratch/chroot/run
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```
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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.
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## Define chroot environment
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*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.*
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> Reference: https://en.wikipedia.org/wiki/Chroot
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1. **Access chroot environment**
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```shell
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sudo chroot $HOME/live-ubuntu-from-scratch/chroot
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```
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2. **Configure mount points, home and locale**
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```shell
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mount none -t proc /proc
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mount none -t sysfs /sys
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mount none -t devpts /dev/pts
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export HOME=/root
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export LC_ALL=C
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```
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These mount points are necessary inside the chroot environment, so we are able to finish the installation without errors.
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3. **Set a custom hostname**
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```shell
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echo "ubuntu-fs-live" > /etc/hostname
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```
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4. **Configure apt sources.list**
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```shell
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cat <<EOF > /etc/apt/sources.list
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deb http://us.archive.ubuntu.com/ubuntu/ focal main restricted universe multiverse
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deb-src http://us.archive.ubuntu.com/ubuntu/ focal main restricted universe multiverse
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deb http://us.archive.ubuntu.com/ubuntu/ focal-security main restricted universe multiverse
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deb-src http://us.archive.ubuntu.com/ubuntu/ focal-security main restricted universe multiverse
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deb http://us.archive.ubuntu.com/ubuntu/ focal-updates main restricted universe multiverse
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deb-src http://us.archive.ubuntu.com/ubuntu/ focal-updates main restricted universe multiverse
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EOF
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```
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5. **Update indexes packages**
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```shell
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apt-get update
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```
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6. **Install systemd**
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```shell
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apt-get install -y libterm-readline-gnu-perl systemd-sysv
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```
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> **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.
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7. **Configure machine-id and divert**
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```shell
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dbus-uuidgen > /etc/machine-id
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ln -fs /etc/machine-id /var/lib/dbus/machine-id
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```
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> 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.
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```shell
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dpkg-divert --local --rename --add /sbin/initctl
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ln -s /bin/true /sbin/initctl
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```
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> **dpkg-divert** is the utility used to set up and update the list of diversions.
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8. **Upgrade packages**
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```shell
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apt-get -y upgrade
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```
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9. **Install packages needed for Live System**
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```shell
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apt-get install -y \
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ubuntu-standard \
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casper \
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lupin-casper \
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discover \
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laptop-detect \
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os-prober \
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network-manager \
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resolvconf \
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net-tools \
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wireless-tools \
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wpagui \
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locales \
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linux-generic
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```
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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.
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1. Configure grub
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<p align="center">
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<img src="images/grub-configure-01.png">
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</p>
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2. Don’t select any options
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<p align="center">
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<img src="images/grub-configure-02.png">
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</p>
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3. Only confirm “Yes”
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<p align="center">
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<img src="images/grub-configure-03.png">
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</p>
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10. **Graphical installer**
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```shell
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apt-get install -y \
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ubiquity \
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ubiquity-casper \
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ubiquity-frontend-gtk \
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ubiquity-slideshow-ubuntu \
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ubiquity-ubuntu-artwork
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```
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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.
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1. Configure keyboard
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<p align="center">
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<img src="images/keyboard-configure-01.png">
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</p>
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<p align="center">
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<img src="images/keyboard-configure-02.png">
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</p>
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2. Console setup
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<p align="center">
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<img src="images/console-configure-01.png">
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</p>
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11. **Install window manager**
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```shell
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apt-get install -y \
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plymouth-theme-ubuntu-logo \
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ubuntu-gnome-desktop \
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ubuntu-gnome-wallpapers
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```
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12. **Install useful applications**
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```shell
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apt-get install -y \
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clamav-daemon \
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terminator \
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apt-transport-https \
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curl \
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vim \
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nano \
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less
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```
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13. **Install Visual Studio Code (optional)**
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1. Download and install the key
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```shell
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curl https://packages.microsoft.com/keys/microsoft.asc | gpg --dearmor > microsoft.gpg
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install -o root -g root -m 644 microsoft.gpg /etc/apt/trusted.gpg.d/
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echo "deb [arch=amd64] https://packages.microsoft.com/repos/vscode stable main" > /etc/apt/sources.list.d/vscode.list
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rm microsoft.gpg
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```
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2. Then update the package cache and install the package using
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```shell
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apt-get update
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apt-get install -y code
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```
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14. **Install Google Chrome (optional)**
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1. Download and install the key
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```shell
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wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add -
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echo "deb http://dl.google.com/linux/chrome/deb/ stable main" > /etc/apt/sources.list.d/google-chrome.list
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```
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2. Then update the package cache and install the package using
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```shell
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apt-get update
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apt-get install google-chrome-stable
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```
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15. **Install Java JDK 8 (optional)**
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```shell
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apt-get install -y \
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openjdk-8-jdk \
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openjdk-8-jre
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```
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16. **Remove unused applications (optional)**
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```shell
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apt-get purge -y \
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transmission-gtk \
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transmission-common \
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gnome-mahjongg \
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gnome-mines \
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gnome-sudoku \
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aisleriot \
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hitori
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```
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17. **Remove unused packages**
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```shell
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apt-get autoremove -y
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```
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18. **Reconfigure packages**
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1. Generate locales
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```shell
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dpkg-reconfigure locales
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```
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1. *Select locales*
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<p align="center">
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<img src="images/locales-select.png">
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</p>
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2. *Select default locale*
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<p align="center">
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<img src="images/locales-default.png">
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</p>
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2. Reconfigure resolvconf
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```shell
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dpkg-reconfigure resolvconf
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```
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1. *Confirm changes*
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<p align="center">
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<img src="images/resolvconf-confirm-01.png">
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</p>
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<p align="center">
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<img src="images/resolvconf-confirm-02.png">
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</p>
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<p align="center">
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<img src="images/resolvconf-confirm-03.png">
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</p>
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3. Configure network-manager
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```shell
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cat <<EOF > /etc/NetworkManager/NetworkManager.conf
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[main]
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rc-manager=resolvconf
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plugins=ifupdown,keyfile
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dns=dnsmasq
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[ifupdown]
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managed=false
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EOF
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```
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4. Reconfigure network-manager
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```shell
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dpkg-reconfigure network-manager
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```
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19. **Cleanup the chroot environment**
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1. If you installed software, be sure to run
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```shell
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truncate -s 0 /etc/machine-id
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```
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2. Remove the diversion
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```shell
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rm /sbin/initctl
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dpkg-divert --rename --remove /sbin/initctl
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```
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3. Clean up
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```shell
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apt-get clean
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rm -rf /tmp/* ~/.bash_history
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umount /proc
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umount /sys
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umount /dev/pts
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export HISTSIZE=0
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exit
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```
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## Unbind mount points
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```shell
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sudo umount $HOME/live-ubuntu-from-scratch/chroot/dev
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sudo umount $HOME/live-ubuntu-from-scratch/chroot/run
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```
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## Create the CD image directory and populate it
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1. Access build directory
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```shell
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cd $HOME/live-ubuntu-from-scratch
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```
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2. Create directories
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```shell
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mkdir -p image/{casper,isolinux,install}
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```
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3. Copy kernel images
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```shell
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sudo cp chroot/boot/vmlinuz-**-**-generic image/casper/vmlinuz
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sudo cp chroot/boot/initrd.img-**-**-generic image/casper/initrd
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```
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4. Copy memtest86+ binary (BIOS)
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```shell
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sudo cp chroot/boot/memtest86+.bin image/install/memtest86+
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```
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5. Download and extract memtest86 binary (UEFI)
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```shell
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wget --progress=dot https://www.memtest86.com/downloads/memtest86-usb.zip -O image/install/memtest86-usb.zip
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unzip -p image/install/memtest86-usb.zip memtest86-usb.img > image/install/memtest86
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rm -f image/install/memtest86-usb.zip
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```
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## Grub configuration
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1. Access build directory
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```shell
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cd $HOME/live-ubuntu-from-scratch
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```
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2. Create base point access file for grub
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```shell
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touch image/ubuntu
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```
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3. Create image/isolinux/grub.cfg
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```shell
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cat <<EOF > image/isolinux/grub.cfg
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search --set=root --file /ubuntu
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insmod all_video
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set default="0"
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set timeout=30
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menuentry "Try Ubuntu FS without installing" {
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linux /casper/vmlinuz boot=casper nopersistent toram quiet splash ---
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initrd /casper/initrd
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}
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menuentry "Install Ubuntu FS" {
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linux /casper/vmlinuz boot=casper only-ubiquity quiet splash ---
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initrd /casper/initrd
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}
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menuentry "Check disc for defects" {
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linux /casper/vmlinuz boot=casper integrity-check quiet splash ---
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initrd /casper/initrd
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}
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menuentry "Test memory Memtest86+ (BIOS)" {
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linux16 /install/memtest86+
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}
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menuentry "Test memory Memtest86 (UEFI, long load time)" {
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insmod part_gpt
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insmod search_fs_uuid
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insmod chain
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loopback loop /install/memtest86
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chainloader (loop,gpt1)/efi/boot/BOOTX64.efi
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}
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EOF
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```
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## Create manifest
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In the next steps the creation of the manifest is important because it tells us which version of each package installed in the Live version and which packages will be removed or maintained in the version that will be installed (persisted in the hard drive).
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1. Access build directory
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```shell
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cd $HOME/live-ubuntu-from-scratch
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```
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2. Generate manifest
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```shell
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sudo chroot chroot dpkg-query -W --showformat='${Package} ${Version}\n' | sudo tee image/casper/filesystem.manifest
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sudo cp -v image/casper/filesystem.manifest image/casper/filesystem.manifest-desktop
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sudo sed -i '/ubiquity/d' image/casper/filesystem.manifest-desktop
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sudo sed -i '/casper/d' image/casper/filesystem.manifest-desktop
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sudo sed -i '/discover/d' image/casper/filesystem.manifest-desktop
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sudo sed -i '/laptop-detect/d' image/casper/filesystem.manifest-desktop
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sudo sed -i '/os-prober/d' image/casper/filesystem.manifest-desktop
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```
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## Compress the chroot
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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.
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1. Access build directory
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```shell
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cd $HOME/live-ubuntu-from-scratch
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```
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2. Create squashfs
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```shell
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sudo mksquashfs chroot image/casper/filesystem.squashfs
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```
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> **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.
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> **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.
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3. Write the filesystem.size
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```shell
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printf $(sudo du -sx --block-size=1 chroot | cut -f1) > image/casper/filesystem.size
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```
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## Create diskdefines
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**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.
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1. Access build directory
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```shell
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cd $HOME/live-ubuntu-from-scratch
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```
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2. Create file image/README.diskdefines
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```shell
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cat <<EOF > image/README.diskdefines
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#define DISKNAME Ubuntu from scratch
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#define TYPE binary
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#define TYPEbinary 1
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#define ARCH amd64
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#define ARCHamd64 1
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#define DISKNUM 1
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#define DISKNUM1 1
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#define TOTALNUM 0
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#define TOTALNUM0 1
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EOF
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```
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## Create ISO Image for a LiveCD (BIOS + UEFI)
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1. Access image directory
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```shell
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cd $HOME/live-ubuntu-from-scratch/image
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```
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2. Create a grub UEFI image
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```shell
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grub-mkstandalone \
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--format=x86_64-efi \
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--output=isolinux/bootx64.efi \
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--locales="" \
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--fonts="" \
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"boot/grub/grub.cfg=isolinux/grub.cfg"
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```
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3. Create a FAT16 UEFI boot disk image containing the EFI bootloader
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```shell
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(
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cd isolinux && \
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dd if=/dev/zero of=efiboot.img bs=1M count=10 && \
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sudo mkfs.vfat efiboot.img && \
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LC_CTYPE=C mmd -i efiboot.img efi efi/boot && \
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LC_CTYPE=C mcopy -i efiboot.img ./bootx64.efi ::efi/boot/
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)
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```
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4. Create a grub BIOS image
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```shell
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grub-mkstandalone \
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--format=i386-pc \
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--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
|
||
|
||
```shell
|
||
cat /usr/lib/grub/i386-pc/cdboot.img isolinux/core.img > isolinux/bios.img
|
||
```
|
||
|
||
6. Generate md5sum.txt
|
||
|
||
```shell
|
||
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
|
||
|
||
```shell
|
||
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" \
|
||
-m "isolinux/efiboot.img" \
|
||
-m "isolinux/bios.img" \
|
||
-graft-points \
|
||
"/EFI/efiboot.img=isolinux/efiboot.img" \
|
||
"/boot/grub/bios.img=isolinux/bios.img" \
|
||
"."
|
||
```
|
||
|
||
## Make a bootable USB image
|
||
|
||
It is simple and easy, using "dd"
|
||
|
||
```shell
|
||
sudo dd if=ubuntu-from-scratch.iso of=<device> status=progress oflag=sync
|
||
```
|