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.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
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.
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.
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 are able to finish the installation without errors.
Set a custom hostname
echo "ubuntu-fs-live" > /etc/hostname
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
Update indexes packages
apt-get update
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.
Configure machine-id and divert
dbus-uuidgen > /etc/machine-id
ln -fs /etc/machine-id /var/lib/dbus/machine-id
The
/etc/machine-idfile 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.
Upgrade packages
apt-get -y upgrade
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
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.
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 less
Install Visual Studio Code (optional)
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 (optional)
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 (optional)
apt-get install -y openjdk-8-jdk openjdk-8-jre
Remove unused applications (optional)
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
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
truncate -s 0 /etc/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
sudo umount $HOME/live-ubuntu-from-scratch/chroot/dev
sudo umount $HOME/live-ubuntu-from-scratch/chroot/run
We are now back in our build environment after setting up our live system and will continue creating files necessary to generate the ISO.
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 memtest86+ binary (BIOS)
sudo cp chroot/boot/memtest86+.bin image/install/memtest86+
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
Access build directory
cd $HOME/live-ubuntu-from-scratch
Create base point access file for grub
touch image/ubuntu
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
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.
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
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.
Access build directory
cd $HOME/live-ubuntu-from-scratch
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.
Write the filesystem.size
printf $(sudo du -sx --block-size=1 chroot | cut -f1) > image/casper/filesystem.size
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.
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
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 && LC_CTYPE=C mmd -i efiboot.img efi efi/boot && LC_CTYPE=C mcopy -i efiboot.img ./bootx64.efi ::efi/boot/
)
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"
Combine a bootable Grub cdboot.img
cat /usr/lib/grub/i386-pc/cdboot.img isolinux/core.img > isolinux/bios.img
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)"
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" "."
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
Include syslinux bios modules
apt install -y syslinux-common && cp /usr/lib/ISOLINUX/isolinux.bin isolinux/ && cp /usr/lib/syslinux/modules/bios/* isolinux/
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"
It is simple and easy, using "dd"
sudo dd if=ubuntu-from-scratch.iso of=<device> status=progress oflag=sync
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.
Please read CONTRIBUTING.md for details on our code of conduct, and the process for submitting pull requests to us.
We use GitHub for versioning. For the versions available, see the tags on this repository.
This project is licensed under the Apache License - see the LICENSE file for details
How to create a custom Ubuntu live from scratch
原文：https://www.cnblogs.com/shamoguzhou/p/15111566.html