从零制作 Ubuntu LiveCD

1. 安装必备工具

sudo apt-get install --no-install-recommends -y debootstrap squashfs-tools grub-efi xorriso dosfstools mtools grub-pc-bin

2. 配置根文件系统

初始化 rootfs

# 创建必要目录
export CHROOT=$PWD/target
sudo mkdir -p $CHROOT livecd/{casper,boot/grub,EFI/boot}

sudo debootstrap --no-check-gpg --variant=minbase --arch=amd64 --exclude=gcc-9-base,gcc-10-base --components=main,restricted,universe,multiverse \
   --include=bash-completion,systemd-sysv,locales,nano,casper,console-setup,netplan.io,whiptail focal $CHROOT https://mirrors.aliyun.com/ubuntu
   
# 配置源
sudo chroot $CHROOT tee /etc/apt/sources.list << EOF
deb https://mirrors.aliyun.com/ubuntu focal main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu focal-security main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu focal-updates main restricted universe multiverse
EOF

挂载

sudo mount -B /dev $CHROOT/dev
sudo chroot $CHROOT mount none -t proc /proc
sudo chroot $CHROOT mount none -t sysfs /sys
sudo chroot $CHROOT mount none -t devpts /dev/pts

sudo chroot $CHROOT apt-get update
sudo chroot $CHROOT env DEBIAN_FRONTEND=noninteractive apt-get upgrade -y

生成 Linux 内核文件

sudo sed -i 's|COMPRESS=lz4|COMPRESS=lzma|' $CHROOT/etc/initramfs-tools/initramfs.conf
sudo chroot $CHROOT apt-get install -y linux-image-generic-hwe-20.04 grub-pc-
sudo mv $CHROOT/boot/vmlinuz-**-**-generic livecd/casper/vmlinuz
sudo mv $CHROOT/boot/initrd.img-**-**-generic livecd/casper/initrd.img

创建默认用户

sudo sed -i 's|\\w|\\W|g' $CHROOT/etc/skel/.bashrc
sudo chroot $CHROOT adduser --gecos '' --disabled-password ubuntu

# 配置网络 https://ubuntu.com/server/docs/network-configuration
sudo tee $CHROOT/etc/netplan/00-networkd.yaml << EOF
network:
   version: 2
   renderer: networkd
   ethernets:
      eth0:
         dhcp4: true
EOF

最小化桌面

sudo chroot $CHROOT env DEBIAN_FRONTEND=noninteractive apt-get install -y fonts-noto-cjk-extra language-pack-gnome-zh-hans ubuntu-desktop-minimal \
   networkd-dispatcher netplan.io firefox- gedit- eog- evince- gnome-characters- gnome-user-docs- gnome-font-viewer- gnome-online-accounts- \
   gnome-disk-utility- gnome-screenshot- gnome-logs- ubuntu-docs- fonts-deva- snapd- cups- cups-*- ibus- ibus-*-
sudo tee $CHROOT/etc/netplan/01-network-manager-all.yaml << EOF
# Let NetworkManager manage all devices on this system
network:
  version: 2
  renderer: NetworkManager
EOF

# 安装搜狗输入法
sudo chroot $CHROOT env DEBIAN_FRONTEND=noninteractive apt-get install -y fcitx libqt5qml5 libqt5quick5 libqt5quickwidgets5 qml-module-qtquick2 libgsettings-qt1
sudo chroot $CHROOT mv /usr/share/applications/fcitx.desktop /etc/xdg/autostart/

添加额外APT源

# 添加 VSCode 源
curl -sL https://packages.microsoft.com/keys/microsoft.asc | sudo gpg --dearmor -o $CHROOT/etc/apt/trusted.gpg.d/microsoft.gpg
echo "deb [arch=amd64] https://packages.microsoft.com/repos/code stable main" | sudo tee $CHROOT/etc/apt/sources.list.d/vscode.list
echo "deb [arch=amd64] https://packages.microsoft.com/repos/edge stable main" | sudo tee $CHROOT/etc/apt/sources.list.d/microsoft-edge.list

# 添加 cmake 源
curl -sL https://apt.kitware.com/keys/kitware-archive-latest.asc | sudo gpg --dearmor -o $CHROOT/etc/apt/trusted.gpg.d/kitware.gpg
echo "deb https://apt.kitware.com/ubuntu/ focal main" | sudo tee $CHROOT/etc/apt/sources.list.d/kitware.list

安装字体

sudo unzip $HOME/fonts.zip -d $CHROOT/usr/share/fonts/truetype/microsoft
sudo chroot $CHROOT env DEBIAN_FRONTEND=noninteractive apt-get install -y gnome-tweaks
sudo chroot $CHROOT su - ubuntu -c "dbus-launch --exit-with-session gsettings set org.gnome.desktop.interface font-name '微软雅黑 11'"

# 额外字体
echo msttcorefonts msttcorefonts/accepted-mscorefonts-eula select true | sudo chroot $CHROOT debconf-set-selections
sudo chroot $CHROOT apt-get install -y ttf-mscorefonts-installer
sudo chroot $CHROOT debconf-show ttf-mscorefonts-installer

清理挂载

sudo chroot $CHROOT apt-get autoremove --purge -y
for i in /dev/pts /dev /proc /sys; do sudo umount $CHROOT$i; done
sudo chroot $CHROOT bash -s << EOF
truncate -s 0 /etc/machine-id
ln -fs /etc/machine-id /var/lib/dbus/machine-id
dpkg-divert --local --rename --add /sbin/initctl
ln -s /bin/true /sbin/initctl
EOF

生成squashfs根文件系统

sudo mksquashfs $CHROOT livecd/casper/filesystem.squashfs -noappend -wildcards -e "var/cache/*" -e "var/log/*" -e "var/lib/apt/lists/*" -e "usr/share/man/*"
sudo chroot $CHROOT dpkg-query -W --showformat='${Package} ${Version}\n' | sudo tee livecd/casper/filesystem.manifest

3. 制作 ISO

# 生成引导菜单
sudo tee livecd/boot/grub/grub.cfg << EOF
search --set=root --file /casper/vmlinuz
insmod all_video
set timeout=30
menuentry "Ubuntu Live" {
   linux /casper/vmlinuz boot=casper net.ifnames=0 locale=zh_CN.UTF-8 toram quiet splash --
   initrd /casper/initrd.img
}
menuentry "Ubuntu persistent" {
   linux /casper/vmlinuz boot=casper net.ifnames=0 locale=zh_CN.UTF-8 persistent quiet splash --
   initrd /casper/initrd.img
}
EOF

# Create a grub UEFI image
sudo grub-mkstandalone --format=x86_64-efi --output=livecd/EFI/boot/bootx64.efi --locales="" --fonts="" \
   "boot/grub/grub.cfg=livecd/boot/grub/grub.cfg"
sudo LC_CTYPE=C bash -s << EOF
dd if=/dev/zero of=efiboot.img bs=1M count=3 && \
mkfs.vfat efiboot.img && \
mmd -i efiboot.img efi efi/boot && \
mcopy -i efiboot.img livecd/EFI/boot/bootx64.efi ::efi/boot/
EOF

# Create a grub BIOS image
sudo grub-mkstandalone --format=i386-pc --output=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=livecd/boot/grub/grub.cfg"
cat /usr/lib/grub/i386-pc/cdboot.img core.img > bios.img

# 制作 UEFI 启动的 ISO
sudo xorriso -as mkisofs -iso-level 3 -full-iso9660-filenames -volid "UBUNTU" -output "/media/downloads/Ubuntu-20.04-LiveCD-x86_64.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 efiboot.img \
   -graft-points "livecd" "/EFI/efiboot.img=efiboot.img" "/boot/grub/bios.img=bios.img"

参考资料
https://github.com/mvallim/live-custom-ubuntu-from-scratch
https://manpages.ubuntu.com/manpages/focal/man7/casper.7.html

1. 安装必备工具

2. 配置根文件系统

3. 制作 ISO

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