Ubuntu 16.04: Create customized LiveDVD

Copy souces.list from host machine to rootfs.

$ sudo cp /etc/apt/sources.list chroot/etc/apt/

Set hostname and add to /etc/hosts which will be used by sudo.

$ echo "ubuntu-live" | sudo tee chroot/etc/hostname
$ echo "127.0.0.1 ubuntu-live" | sudo tee chroot/etc/hosts

Set root passwd with chroot.

$ sudo chroot chroot
# passwd
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
# exit

Start container with systemd-nspawn.

$ sudo systemd-nspawn -b -D chroot
<snip>
[  OK  ] Started Update UTMP about System Runlevel Changes.

Ubuntu 16.04 LTS localhost.localdomain console

localhost login: root
Password:
Welcome to Ubuntu 16.04 LTS (GNU/Linux 4.4.0-22-generic x86_64)

 * Documentation:  https://help.ubuntu.com/

The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.

root@ubuntu-live:~#

Update package list.

# apt update -y

Installing live-boot package and live-boot-initramfs-tools package, and setting "boot=live" to kernel parameter, LiveDVD can be run. "boot=casper" is for installer which can eject DVD when shutdown.

# apt install -y live-boot live-boot-initramfs-tools

Install GRUB2 and linux kernel. This is for using grub-mkconfig and loading kernel.

# apt install -y grub2-common
# apt install -y linux-image-$(uname -r)

Install kbd package for non-English keyboard. This article uses Japanese keyboard.

# apt install -y kbd
# sed -i 's/exit 0/loadkeys jp/g' /etc/rc.local
# echo "exit 0" >> /etc/rc.local

This article uses LiveDVD for rescue Ubuntu, e.g. fsck and lvm backup.

# apt install -y network-manager openssh-server openssh-client \
byobu emacs less lvm2 e2fsprogs net-tools

When running ssh server on host, openssh-server's postinst will be failed, but it does not need to take care of it.

Errors were encountered while processing:
 openssh-server
E: Sub-process /usr/bin/dpkg returned an error code (1)

systemd-nspawn can use systemctl.

$ sudo systemctl enable ssh

After creating user, run hash command for PATH searching.

# useradd -m -s /bin/bash hiroom2
# gpasswd -a hiroom2 sudo
Adding user hiroom2 to group sudo
# passwd hiroom2
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
# su - hiroom2
$ hash -r && hash
$ exit

This article sets .ssh and .byobu.

Create grub.cfg which can use serial console. And add "boot=live" to kernel parameter. This will run scripts/live in initrd.

# cat <<EOF | tee /boot/grub/grub.cfg
set timeout=1

serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1
terminal_input console serial
terminal_output console serial

menuentry 'ubuntu-live' {
  linux /boot/vmlinuz-4.4.0-22-generic boot=live console=tty1 console=ttyS0,115200
  initrd /boot/initrd.img-4.4.0-22-generic
}
EOF

Shtudown container and return to host.

# poweroff

Create directory for iso.

$ mkdir iso
$ mkdir iso/live

Copy boot directory to iso. GRUB will load kernel and initrd from this directory.

$ sudo cp -a chroot/boot iso/

Create squashfs from chroot directory and copy to iso directory. If you have already created filesystem.squashfs, you must remove previous filesystem.squashfs before creation. If you do not remove previous filesystem.squashfs, there will be duplicated directories like /etc and /etc_1, or /var and /var_1.

$ sudo mksquashfs chroot iso/live/filesystem.squashfs

Create iso which is installed GRUB2.

$ sudo grub-mkrescue -o ubuntu-live.iso iso

LiveDVD will start with running this iso on BIOS.