Process

Process

This is a basic breakdown of the process involed:

• Install required packages
• Make work directories
• Get ISO
• Mount base ISO as loopback device so contents can be copied
• Copy contents of ISO to a RW location so we can work with them
• Mount squashfs and copy giles into it
• Create a chroot script and execute it
• Uncompress ISO into directory and create autoinstall shell
• Create ISO autoinstall files
• Create ISO grub file menu that calls autoinstall file(s)
• Create ISO file

Install Required Packages

sudo apt install -y p7zip-full wget xorriso

Make Work Directories

mkdir -p ./isomount ./isonew/squashfs ./isonew/cd ./isonew/custom

Get ISO

wget https://releases.ubuntu.com/22.04.1/ubuntu-22.04.1-live-server-amd64.iso -O ./ubuntu-iso/ubuntu-22.04.1-live-server-amd64.iso

Mount ISO

sudo mount -o loop ./ubuntu-22.04.1-live-server-amd64.iso ./isomount

Copy ISO

rsync --exclude=/casper/ubuntu-server-minimal.squashfs -av ./isomount/ ./isonew/cd
rsync -av ./isomount/ ./isonew/cd

Mount Squashfs

sudo mount -t squashfs -o loop ./isomount/casper/ubuntu-server-minimal.squashfs ./isonew/squashfs/
sudo rsync -av ./isonew/squashfs/ ./isonew/custom
sudo cp /etc/resolv.conf /etc/hosts ./isonew/custom/etc/
sudo cp /etc/apt/sources.list ./isonew/custom/etc/apt/

Create chroot

Create chroot script:

cat <<EOF > ./ubuntu-iso/isonew/custom/tmp/modify_chroot.sh
#!/usr/bin/bash
mount -t proc none /proc/
mount -t sysfs none /sys/
mount -t devpts none /dev/pts
export HOME=/root
sudo apt update
sudo apt install -y --download-only zfsutils-linux grub-efi zfs-initramfs net-tools curl wget
sudo apt install -y zfsutils-linux grub-efi zfs-initramfs net-tools curl wget
umount /proc/
umount /sys/
umount /dev/pts/
exit
EOF

This script install the required ZFS and other packages into the squashfs filewsystem. It also also downloads a copy of the packages so we can copy this into ISO we create, so they can be installed as part of the installation method without requiring network.

Execute chroot script:

sudo chmod +x ./ubuntu-iso/isonew/custom/tmp/modify_chroot.sh
sudo chroot ./ubuntu-iso/isonew/custom /tmp/modify_chroot.sh

Uncompress ISO

Uncompress ISO and move BOOT files to where they will be used by ISO creation process:

7z -y x ./ubuntu-iso/ubuntu-22.04.1-live-server-amd64.iso -o./ubuntu-iso/source-files
mv ./source-files/\[BOOT\] ./BOOT

Creat directories for autoinstall configs:

mkdir -p ./source-files/autoinstall/configs/sda
mkdir -p ./source-files/autoinstall/packages
touch ./source-files/autoinstall/configs/sda/meta-data

Copy packages we downloaded as part of chroot process so they can be included on the ISO:

cp ./isonew/custom/var/cache/apt/archives/*.deb source-files/autoinstall/packages/

Create autoinstall Files

This example uses /dev/sda as a ZFS root device. The documentation for this process is hard to find, so the example is a simple unmirrored device, as this works. A mirror could be done as a post script or after install.

An example of getting a password crypt:

export PASSWORD_CRYPT=$(echo P455w0rD |mkpasswd --method=SHA-512 --stdin)

Create a user-data file:

cat <<EOF > ./source-files/autoinstall/configs/sda/user-data
#cloud-config
autoinstall:
 apt:
   preferences:
     - package: "*"
       pin: "release a=jammy-security"
       pin-priority: 200
   disable_components: []
   geoip: true
   preserve_sources_list: false
   primary:
   - arches:
     - amd64
     - i386
     uri: http://archive.ubuntu.com/ubuntu
   - arches:
     - default
     uri: http://ports.ubuntu.com/ubuntu-ports
 package_update: false
 package_upgrade: false
 drivers:
   install: false
 user-data:
   timezone: Australia/Melbourne
 identity:
   hostname: ubuntu
   password: "$PASSWORD_CRYPT"
   realname: Ubuntu
   username: ubuntu
 kernel:
   package: linux-generic
 keyboard:
   layout: us
 locale: en_US.UTF-8
 network:
   ethernets:
     ens33:
       critical: true
       dhcp-identifier: mac
       dhcp4: true
   version: 2
 ssh:
   allow-pw: true
   authorized-keys: []
   install-server: true
 storage:
   config:
   - ptable: gpt
     path: /dev/sda
     wipe: superblock-recursive
     preserve: false
     name: ''
     grub_device: true
     type: disk
     id: disk1
   - device: disk1
     size: 1127219200
     wipe: superblock-recursive
     flag: boot
     number: 1
     preserve: false
     grub_device: true
     type: partition
     ptable: gpt
     id: disk1p1
   - fstype: fat32
     volume: disk1p1
     preserve: false
     type: format
     id: disk1p1fs1
   - path: /boot/efi
     device: disk1p1fs1
     type: mount
     id: mount-2
   - device: disk1
     size: -1
     wipe: superblock-recursive
     flag: root
     number: 2
     preserve: false
     grub_device: false
     type: partition
     id: disk1p2
   - id: disk1p2fs1
     type: format
     fstype: zfsroot
     volume: disk1p2
     preserve: false
   - id: disk1p2f1_rootpool
     mountpoint: /
     pool: rpool
     type: zpool
     device: disk1p2fs1
     preserve: false
     vdevs:
       - disk1p2fs1
   - id: disk1_rootpool_container
     pool: disk1p2f1_rootpool
     preserve: false
     properties:
       canmount: "off"
       mountpoint: "none"
     type: zfs
     volume: /ROOT
   - id: disk1_rootpool_rootfs
     pool: disk1p2f1_rootpool
     preserve: false
     properties:
       canmount: noauto
       mountpoint: /
     type: zfs
     volume: /ROOT/zfsroot
   - path: /
     device: disk1p2fs1
     type: mount
     id: mount-disk1p2
   swap:
     swap: 0
 early-commands:
   - "sudo dpkg --auto-deconfigure --force-depends -i /cdrom/autoinstall/packages/*.deb"
 version: 1
EOF

Create ISO grub File

Greate grub file:

cat <<EOF > ./source-files/boot/grub/grub.cfg
set timeout=10
loadfont unicode
set menu_color_normal=white/black
set menu_color_highlight=black/light-gray
menuentry "Autoinstall Ubuntu Server - Physical" {
   set gfxpayload=keep
   linux   /casper/vmlinuz quiet autoinstall ds=nocloud\;s=/cdrom/autoinstall/configs/sda/  ---
   initrd  /casper/initrd
}
menuentry "Try or Install Ubuntu Server" {
 set gfxpayload=keep
 linux /casper/vmlinuz quiet ---
 initrd  /casper/initrd
}
menuentry 'Boot from next volume' {
 exit 1
}
menuentry 'UEFI Firmware Settings' {
 fwsetup
}
EOF

Create ISO File

Get required partition information from existing ISO:

export APPEND_PARTITION=$(xorriso -indev ubuntu-22.04.1-live-server-amd64.iso -report_el_torito as_mkisofs |grep append_partition |tail -1 |awk '{print $3}' 2>&1)
export ISO_MBR_PART_TYPE=$(xorriso -indev ubuntu-22.04.1-live-server-amd64.iso -report_el_torito as_mkisofs |grep iso_mbr_part_type |tail -1 |awk '{print $2}' 2>&1)

Create ISO:

xorriso -as mkisofs -r -V 'Ubuntu-Server 22.04.1 LTS arm64' -o ../ubuntu-22.04-autoinstall-arm64.iso --grub2-mbr \
../BOOT/Boot-NoEmul.img -partition_offset 16 --mbr-force-bootable -append_partition 2 $APPEND_PARTITION ../BOOT/Boot-NoEmul.img \
-appended_part_as_gpt -iso_mbr_part_type $ISO_MBR_PART_TYPE -c '/boot/boot.cat' -e '--interval:appended_partition_2:::' -no-emul-boot