script for building custom Ubuntu iso
#!/bin/bash
# from original source https://raw.githubusercontent.com/covertsh/ubuntu-autoinstall-generator/main/ubuntu-autoinstall-generator.sh
# 2024-04-26 - added support for 24.04 LTS (Magnus Bergdahl)
#
#
set -Eeuo pipefail
function cleanup() {
trap - SIGINT SIGTERM ERR EXIT
if [ -n "${tmpdir+x}" ]; then
rm -rf "$tmpdir"
log "🚽 Deleted temporary working directory $tmpdir"
fi
}
trap cleanup SIGINT SIGTERM ERR EXIT
script_dir=$(cd "$(dirname "${BASH_SOURCE[0]}")" &>/dev/null && pwd -P)
[[ ! -x "$(command -v date)" ]] && echo "💥 date command not found." && exit 1
today=$(date +"%Y-%m-%d")
function log() {
echo >&2 -e "[$(date +"%Y-%m-%d %H:%M:%S")] ${1-}"
}
function die() {
local msg=$1
local code=${2-1} # Bash parameter expansion - default exit status 1. See https://wiki.bash-hackers.org/syntax/pe#use_a_default_value
log "$msg"
exit "$code"
}
usage() {
cat <<EOF
Usage: $(basename "${BASH_SOURCE[0]}") [-h] [-v] [-a] [-e] [-u user-data-file] [-m meta-data-file] [-k] [-c] [-r] [-s source-iso-file] [-d destination-iso-file]
💁 This script will create fully-automated Ubuntu 24.04 Noble Numbat installation media.
Available options:
-h, --help Print this help and exit
-v, --verbose Print script debug info
-a, --all-in-one Bake user-data and meta-data into the generated ISO. By default you will
need to boot systems with a CIDATA volume attached containing your
autoinstall user-data and meta-data files.
For more information see: https://ubuntu.com/server/docs/install/autoinstall-quickstart
-e, --use-hwe-kernel Force the generated ISO to boot using the hardware enablement (HWE) kernel. Not supported
by early Ubuntu 20.04 release ISOs.
-u, --user-data Path to user-data file. Required if using -a
-u2, --user-data Path to 2nd user-data file. Required if using -a
-m, --meta-data Path to meta-data file. Will be an empty file if not specified and using -a
-k, --no-verify Disable GPG verification of the source ISO file. By default SHA256SUMS-$today and
SHA256SUMS-$today.gpg in ${script_dir} will be used to verify the authenticity and integrity
of the source ISO file. If they are not present the latest daily SHA256SUMS will be
downloaded and saved in ${script_dir}. The Ubuntu signing key will be downloaded and
saved in a new keyring in ${script_dir}
-c, --no-md5 Disable MD5 checksum on boot
-r, --use-release-iso Use the current release ISO instead of the daily ISO. The file will be used if it already
exists.
-s, --source Source ISO file. By default the latest daily ISO for Ubuntu 24.04 daily build will be downloaded
and saved as ${script_dir}/ubuntu-original-$today.iso
That file will be used by default if it already exists.
-d, --destination Destination ISO file. By default ${script_dir}/ubuntu-autoinstall-$today.iso will be
created, overwriting any existing file.
EOF
exit
}
function parse_params() {
# default values of variables set from params
user_data_file=''
user_data_file2=''
meta_data_file=''
download_url="https://mirror.bahnhof.net/ubuntu-releases/24.04.4"
download_iso="ubuntu-24.04.4-desktop-amd64.iso"
original_iso="ubuntu-original-$today.iso"
source_iso="${script_dir}/${original_iso}"
destination_iso="${script_dir}/ubuntu-autoinstall-$today.iso"
sha_suffix="${today}"
gpg_verify=1
all_in_one=0
use_hwe_kernel=0
md5_checksum=1
use_release_iso=0
while :; do
case "${1-}" in
-h | --help) usage ;;
-v | --verbose) set -x ;;
-a | --all-in-one) all_in_one=1 ;;
-e | --use-hwe-kernel) use_hwe_kernel=1 ;;
-c | --no-md5) md5_checksum=0 ;;
-k | --no-verify) gpg_verify=0 ;;
-r | --use-release-iso) use_release_iso=1 ;;
-u | --user-data)
user_data_file="${2-}"
shift
;;
-u2 | --user-data)
user_data_file2="${2-}"
shift
;;
-s | --source)
source_iso="${2-}"
shift
;;
-d | --destination)
destination_iso="${2-}"
shift
;;
-m | --meta-data)
meta_data_file="${2-}"
shift
;;
-?*) die "Unknown option: $1" ;;
*) break ;;
esac
shift
done
log "👶 Starting up..."
# check required params and arguments
if [ ${all_in_one} -ne 0 ]; then
[[ -z "${user_data_file}" ]] && die "💥 user-data file was not specified."
[[ ! -f "$user_data_file" ]] && die "💥 user-data file could not be found."
[[ -n "${meta_data_file}" ]] && [[ ! -f "$meta_data_file" ]] && die "💥 meta-data file could not be found."
fi
if [ "${source_iso}" != "${script_dir}/${original_iso}" ]; then
[[ ! -f "${source_iso}" ]] && die "💥 Source ISO file could not be found."
fi
if [ "${use_release_iso}" -eq 1 ]; then
download_url="https://releases.ubuntu.com/24.04"
log "🔎 Checking for current release..."
download_iso=$(curl -sSL "${download_url}" | grep -oP 'ubuntu\-\24.04.4\-\desktop-amd64\.iso' | head -n 1)
original_iso="${download_iso}"
source_iso="${script_dir}/${download_iso}"
current_release=$(echo "${download_iso}" | cut -f2 -d-)
sha_suffix="${current_release}"
log "💿 Current release is ${current_release}"
fi
destination_iso=$(realpath "${destination_iso}")
source_iso=$(realpath "${source_iso}")
return 0
}
ubuntu_gpg_key_id="843938DF228D22F7B3742BC0D94AA3F0EFE21092"
parse_params "$@"
tmpdir=$(mktemp -d)
if [[ ! "$tmpdir" || ! -d "$tmpdir" ]]; then
die "💥 Could not create temporary working directory."
else
log "📁 Created temporary working directory $tmpdir"
fi
log "🔎 Checking for required utilities..."
[[ ! -x "$(command -v xorriso)" ]] && die "💥 xorriso is not installed. On Ubuntu, install the 'xorriso' package."
[[ ! -x "$(command -v sed)" ]] && die "💥 sed is not installed. On Ubuntu, install the 'sed' package."
[[ ! -x "$(command -v curl)" ]] && die "💥 curl is not installed. On Ubuntu, install the 'curl' package."
[[ ! -x "$(command -v gpg)" ]] && die "💥 gpg is not installed. On Ubuntu, install the 'gpg' package."
[[ ! -f "/usr/lib/ISOLINUX/isohdpfx.bin" ]] && die "💥 isolinux is not installed. On Ubuntu, install the 'isolinux' package."
log "👍 All required utilities are installed."
if [ ! -f "${source_iso}" ]; then
log "🌎 Downloading ISO image for Ubuntu 24.04.4 Noble Numbat..."
curl -NsSL "${download_url}/${download_iso}" -o "${source_iso}"
log "👍 Downloaded and saved to ${source_iso}"
else
log "☑️ Using existing ${source_iso} file."
if [ ${gpg_verify} -eq 1 ]; then
if [ "${source_iso}" != "${script_dir}/${original_iso}" ]; then
log "⚠️ Automatic GPG verification is enabled. If the source ISO file is not the latest daily or release image, verification will fail!"
fi
fi
fi
if [ ${gpg_verify} -eq 1 ]; then
if [ ! -f "${script_dir}/SHA256SUMS-${sha_suffix}" ]; then
log "🌎 Downloading SHA256SUMS & SHA256SUMS.gpg files..."
curl -NsSL "${download_url}/SHA256SUMS" -o "${script_dir}/SHA256SUMS-${sha_suffix}"
curl -NsSL "${download_url}/SHA256SUMS.gpg" -o "${script_dir}/SHA256SUMS-${sha_suffix}.gpg"
else
log "☑️ Using existing SHA256SUMS-${sha_suffix} & SHA256SUMS-${sha_suffix}.gpg files."
fi
if [ ! -f "${script_dir}/${ubuntu_gpg_key_id}.keyring" ]; then
log "🌎 Downloading and saving Ubuntu signing key..."
gpg -q --no-default-keyring --keyring "${script_dir}/${ubuntu_gpg_key_id}.keyring" --keyserver "hkp://keyserver.ubuntu.com" --recv-keys "${ubuntu_gpg_key_id}"
log "👍 Downloaded and saved to ${script_dir}/${ubuntu_gpg_key_id}.keyring"
else
log "☑️ Using existing Ubuntu signing key saved in ${script_dir}/${ubuntu_gpg_key_id}.keyring"
fi
log "🔐 Verifying ${source_iso} integrity and authenticity..."
gpg -q --keyring "${script_dir}/${ubuntu_gpg_key_id}.keyring" --verify "${script_dir}/SHA256SUMS-${sha_suffix}.gpg" "${script_dir}/SHA256SUMS-${sha_suffix}" 2>/dev/null
if [ $? -ne 0 ]; then
rm -f "${script_dir}/${ubuntu_gpg_key_id}.keyring~"
die "👿 Verification of SHA256SUMS signature failed."
fi
rm -f "${script_dir}/${ubuntu_gpg_key_id}.keyring~"
digest=$(sha256sum "${source_iso}" | cut -f1 -d ' ')
set +e
grep -Fq "$digest" "${script_dir}/SHA256SUMS-${sha_suffix}"
if [ $? -eq 0 ]; then
log "👍 Verification succeeded."
set -e
else
die "👿 Verification of ISO digest failed."
fi
else
log "🤞 Skipping verification of source ISO."
fi
log "🔧 Extracting ISO image..."
7z -y x ${source_iso} -o$tmpdir #&>/dev/null
#xorriso -osirrox on -indev "${source_iso}" -extract / "$tmpdir" &>/dev/null
chmod -R u+w "$tmpdir"
# rm -rf "$tmpdir/"'[BOOT]'
# Move BOOT directory outside, since this is not needed in the final iso.
mv --force "$tmpdir/"'[BOOT]' /tmp/BOOT
log "👍 Extracted to $tmpdir"
if [ ${use_hwe_kernel} -eq 1 ]; then
if grep -q "hwe-vmlinuz" "$tmpdir/boot/grub/grub.cfg"; then
log "☑️ Destination ISO will use HWE kernel."
sed -i -e 's|/casper/vmlinuz|/casper/hwe-vmlinuz|g' "$tmpdir/boot/grub/grub.cfg"
sed -i -e 's|/casper/initrd|/casper/hwe-initrd|g' "$tmpdir/boot/grub/grub.cfg"
sed -i -e 's|/casper/vmlinuz|/casper/hwe-vmlinuz|g' "$tmpdir/boot/grub/loopback.cfg"
sed -i -e 's|/casper/initrd|/casper/hwe-initrd|g' "$tmpdir/boot/grub/loopback.cfg"
else
log "⚠️ This source ISO does not support the HWE kernel. Proceeding with the regular kernel."
fi
fi
log "🧩 Adding autoinstall parameter to kernel command line..."
if [ ${all_in_one} -eq 1 ]; then
log "🧩 Adding user-data and meta-data files..."
mkdir "$tmpdir/nocloud"
mkdir "$tmpdir/nocloud2"
cp "$user_data_file" "$tmpdir/nocloud/user-data"
cp "$user_data_file2" "$tmpdir/nocloud2/user-data"
log "🧩 Adding packages files..."
cp -a "$HOME/ubuntu-desktop-config/packages/" "$tmpdir"
cp -a "$HOME/ubuntu-desktop-config/scripts/" "$tmpdir/nocloud"
cp -a "$HOME/ubuntu-desktop-config/scripts2/" "$tmpdir/nocloud2"
if [ -n "${meta_data_file}" ]; then
cp "$meta_data_file" "$tmpdir/nocloud/meta-data"
else
touch "$tmpdir/nocloud/meta-data"
touch "$tmpdir/nocloud2/meta-data"
fi
# Find the position to insert the new menuentry
menu_pos=13
# Create a new menuentry with autoinstall parameter and nocloud data source
new_entry='menuentry "Ubuntu 24.04 LTS encrypted install" {\n\tset gfxpayload=keep\n\tlinux /casper/vmlinuz layerfs-path=minimal.standard.live.squashfs autoinstall ds=nocloud\\;s=/cdrom/nocloud/ --- quiet splash\n\tinitrd /casper/initrd\n}'
# Insert the new menuentry into grub.cfg
sed -i "${menu_pos}i ${new_entry}" "$tmpdir/boot/grub/grub.cfg"
# Insert the same menuentry into loopback.cfg
sed -i "${menu_pos}i ${new_entry}" "$tmpdir/boot/grub/loopback.cfg"
log "👍 Added data and configured kernel command line for ENCRYPTED install."
# Find the position to insert the new menuentry
menu_pos=18
# Create a new menuentry with autoinstall parameter and nocloud data source
new_entry='menuentry "Ubuntu 24.04 LTS interactive install" {\n\tset gfxpayload=keep\n\tlinux /casper/vmlinuz layerfs-path=minimal.standard.live.squashfs autoinstall ds=nocloud\\;s=/cdrom/nocloud2/ --- quiet splash\n\tinitrd /casper/initrd\n}'
# Insert the new menuentry into grub.cfg
sed -i "${menu_pos}i ${new_entry}" "$tmpdir/boot/grub/grub.cfg"
# Insert the same menuentry into loopback.cfg
sed -i "${menu_pos}i ${new_entry}" "$tmpdir/boot/grub/loopback.cfg"
log "👍 Added data and configured kernel command line for INTERACTIVE install."
fi
if [ ${md5_checksum} -eq 1 ]; then
log "👷 Updating $tmpdir/md5sum.txt with hashes of modified files..."
md5=$(md5sum "$tmpdir/boot/grub/grub.cfg" | cut -f1 -d ' ')
sed -i -e 's,^.*[ ] ./boot/grub/grub.cfg,'"$md5"' ./boot/grub/grub.cfg,' "$tmpdir/md5sum.txt"
md5=$(md5sum "$tmpdir/boot/grub/loopback.cfg" | cut -f1 -d ' ')
sed -i -e 's,^.*[ ] ./boot/grub/loopback.cfg,'"$md5"' ./boot/grub/loopback.cfg,' "$tmpdir/md5sum.txt"
log "👍 Updated hashes."
else
log "🗑️ Clearing MD5 hashes..."
echo > "$tmpdir/md5sum.txt"
log "👍 Cleared hashes."
fi
log "📦 Repackaging extracted files into an ISO image..."
cd "$tmpdir"
xorriso -as mkisofs -r \
-V "Ubuntu 24.04.4 LTS amd64" \
-o "${destination_iso}" \
--grub2-mbr /tmp/BOOT/1-Boot-NoEmul.img \
-partition_offset 16 \
--mbr-force-bootable \
-append_partition 2 0xef /tmp/BOOT/2-Boot-NoEmul.img \
-appended_part_as_gpt \
-iso_mbr_part_type a2a0d0ebe5b9334487c068b6b72699c7 \
-c boot.catalog \
-b boot/grub/i386-pc/eltorito.img \
-no-emul-boot \
-boot-load-size 4 \
-boot-info-table \
--grub2-boot-info \
-eltorito-alt-boot \
-e "--interval:appended_partition_2:::" \
-no-emul-boot \
"${tmpdir}" &>/dev/null
rm -rf /tmp/BOOT
log "👍 Repackaged into ${destination_iso}"
die "✅ Completed." 0
I use this script to download and build my iso.
I place it in a folder I called ubuntu-desktop-config and have subfolders packages, scripts and scripts2 under it.
place two files under ubuntu-desktop-config , called user-data and user-data2 (see below)
folders:
ubuntu-desktop-config/scripts (scripts for luks encrypted zero touch install)
ubuntu-desktop-config/scripts2 (scripts for semi-interactive non-encrypted install)
files:
ubuntu-desktop-config/user-data (the autoinstall-file in yaml-format for luks encrypted zero touch install)
ubuntu-desktop-config/user-data (the autoinstall-file in yaml-format for semi-interactive non-encrypted install
ubuntu-desktop-config/ubuntu-autoinstall-generator.sh (this script above)
command:
ubuntu-autoinstall-generator.sh -a -u user-data -u2 user-data2
This will download and original iso as file name as ubuntu-original-.iso and then after if all is well create a custom iso named ubuntu-autoinstall-.
You might wanna change server that it downloads from as I have a swedish one in there.
I hope this helps.