build-image.sh

#!/bin/bash

set -ex

CONFIG_FILE="$(cat $1 | yq)"
echo $CONFIG_FILE

function phase1() {
    WORKDIR=$1
    IMAGE_NAME=$2
    IMAGE_SIZE=$3

   pushd $WORKDIR &>$WORKDIR/phase1.log

    echo "PHASE-1: create image"
    BLOCKS=$(numfmt --from=iec $IMAGE_SIZE)
    ESP=$(numfmt --from=iec 512M)
    BLOCKS=$(($ESP + $BLOCKS))
    dd if=/dev/zero of=$IMAGE_NAME bs=1 count=0 seek=$BLOCKS &>>phase1.log

   echo "PHASE-1: create partitions"

    cat <<EOF | sfdisk $IMAGE_NAME &>>phase1.log
label: gpt
unit: sectors
first-lba: 2048
sector-size: 512

2048 +512M U
- $IMAGE_SIZE L
EOF

    export LOOP=$(losetup --show -fP $IMAGE_NAME)
    losetup -l $LOOP &>>phase1.log
    fdisk -l $LOOP &>>phase1.log

    echo "PHASE-1: create filesystems"
    mkfs.vfat $(echo $LOOP"p1") &>>phase1.log
    mkfs.ext4 $(echo $LOOP"p2") &>>phase1.log
    popd &>>phase1.log
}

function phase2() {
    WORKDIR=$1
    LOOP=$2
    DISTRO=$(echo $CONFIG_FILE | jq -r '.image.distro')
    MIRROR="http://nl.archive.ubuntu.com/ubuntu/"
    P1=$(echo $LOOP"p1")
    P2=$(echo $LOOP"p2")

    pushd $WORKDIR &>$WORKDIR/phase2.log

    echo "PHASE-2: Setup default mounts"
    mkdir chroot
    mount $P2 chroot
    mkdir -p chroot/boot
    mkdir -p chroot/boot/efi
    mount $P1 chroot/boot/efi

    echo "PHASE-2: Setup default content"
    debootstrap \
        --arch=amd64 \
        --variant=minbase \
        --components "main,universe" \
        --include "ca-certificates,cron,iptables,isc-dhcp-client,libnss-myhostname,ntp,ntpdate,rsyslog,ssh,sudo,dialog,whiptail,man-db,curl,dosfstools,e2fsck-static" \
        $DISTRO \
        chroot \
        $MIRROR &>>phase2.log

    rm -rf chroot/var/cache/apt/*
    mount --bind /dev chroot/dev
    mount --bind /run chroot/run

    mkdir -p $WORKDIR/chroot/install
    popd &>>phase2.log

    echo "PHASE-2: Setup custom content"
    CONTENT_DIR=$(echo $CONFIG_FILE | jq -r '.content.base')
    pushd $CONTENT_DIR
    cp -avr . $WORKDIR/chroot/install
    popd

    LOCAL_PACKAGE_DIR=$(echo $CONFIG_FILE | jq -r '.content.local_package_dir')
    mkdir -p $WORKDIR/chroot/install/packages
    cp -v $LOCAL_PACKAGE_DIR/*.deb $WORKDIR/chroot/install/packages
    mkdir -p $WORKDIR/chroot/install/scripts
}

function phase3() {
    WORKDIR=$1
    export LOOP=$2
    export HOSTNAME=testhost
    export DISTRO=$(echo $CONFIG_FILE | jq -r '.image.distro')

    P2=$(echo $LOOP"p2")

    export $(blkid -o export $P2 | grep UUID)
    export P2_UUID=$UUID

    echo "PHASE-3: create install and config files in image"
    cat <<EOF >$WORKDIR/chroot/etc/apt/sources.list
deb http://archive.ubuntu.com/ubuntu/ $DISTRO main universe
deb-src http://archive.ubuntu.com/ubuntu/ $DISTRO main universe

deb http://archive.ubuntu.com/ubuntu/ $DISTRO-security main universe
deb-src http://archive.ubuntu.com/ubuntu/ $DISTRO-security main universe

deb http://archive.ubuntu.com/ubuntu/ $DISTRO-updates main universe
deb-src http://archive.ubuntu.com/ubuntu/ $DISTRO-updates main universe
EOF

    cat <<EOF >$WORKDIR/chroot/etc/fstab
# /etc/fstab: static file system information.
# <file system>         <mount point>   <type>  <options>                       <dump>  <pass>
/dev/disk/by-uuid/$P2_UUID      /               ext4    errors=remount-ro               0       1
EOF

    cat <<EOF >$WORKDIR/chroot/install/phase3a.sh
mount  none -t proc /proc
mount none -t sysfs /sys
mount none -t devpts /dev/pts
mount none -t tmpfs /var/cache/apt
mount none -t tmpfs /var/lib/apt

mkdir -p /usr/lib/firmware
mount none -t tmpfs /usr/lib/firmware
export HOME=/root
export LC_ALL=C
echo "$HOSTNAME" > /etc/hostname
exit
EOF

    cat <<EOF >$WORKDIR/chroot/install/phase3b.sh
apt update
apt -qq install -y systemd-sysv
dbus-uuidgen > /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

apt -qq --no-install-recommends install -y \
    ubuntu-server-minimal \
    linux-image-generic  \
    systemd-repart \
    zstd \
    grub-efi-amd64
exit
EOF

    cat <<EOF >$WORKDIR/chroot/install/phase3c.sh
grub-install --target=x86_64-efi $LOOP --efi-directory=/boot/efi --boot-directory=/boot
update-grub
exit
EOF

    cat <<EOF >$WORKDIR/chroot/install/phase3d.sh
    apt -qq --yes --force-yes install $(echo $CONFIG_FILE | jq -jr '(.content.apt_packages//[]).[]|. + " "')
    pushd /install/packages &>/dev/null
    $(echo $CONFIG_FILE | jq -r '(.content.local_packages//[]).[]|"find . -name \"*" + . + "*\" -exec apt -qq --yes --force-yes install {} \\;"')
    if test -d /install/skel; then
      pushd /install/skel
      cp -vaf . /
      popd
    fi
    popd &>/dev/null
    pushd /install/scripts &>/dev/null
    find . -name "*.sh" -exec chmod a+x {} \;
    popd &>/dev/null
    $(echo $CONFIG_FILE | jq -r '(.content.scripts//[]).[]|"/install/scripts/"+.')
EOF

    cat <<EOF >$WORKDIR/chroot/install/phase4a.sh
apt -qq -y upgrade

echo 'root:root' | chpasswd

truncate -s 0 /etc/machine-id
rm /sbin/initctl
dpkg-divert --rename --remove /sbin/initctl
apt-get clean
rm -rf /tmp/* ~/.bash_history
rm -rf /install
export HISTSIZE=0
 
ls -lR /var/lib/snapd

exit
EOF


    echo "PHASE-3a: setup mount points"
    chroot $WORKDIR/chroot bash -e /install/phase3a.sh &>$WORKDIR/phase3a.log
    echo "PHASE-3b: install default ubuntu packages and kernel"
    chroot $WORKDIR/chroot bash -e /install/phase3b.sh &>$WORKDIR/phase3b.log
    echo "PHASE-3c: setup boot partition"
    chroot $WORKDIR/chroot bash -e /install/phase3c.sh &>$WORKDIR/phase3c.log
    echo "PHASE-3d: custom packages and scripts from content"
    chroot $WORKDIR/chroot bash -e /install/phase3d.sh
    echo "PHASE-4a: upgrade all and cleanup in image"
    cat $WORKDIR/chroot/install/phase4a.sh
    chroot $WORKDIR/chroot bash -ex /install/phase4a.sh &>$WORKDIR/phase4a.log

}

function phase4() {
    WORKDIR=$1
    TYPE=$2
    echo "PHASE-4b: cleanup build $TYPE"

    MOUNTS=$(mount | grep $WORKDIR/chroot | cut -f 3 -d ' ' | sort -r)
    for MOUNT in $MOUNTS; do
        umount $MOUNT || continue
    done

    if [ "$TYPE" == "normal" ]; then
        P2=$(echo $LOOP"p2")
        e2fsck -f -y $P2
        resize2fs -M $P2
        losetup -d $LOOP
    else
        losetup -d $LOOP || true
    fi

}

BASEDIR="$(echo $CONFIG_FILE | jq -r '.config.workdir')"
if test -d $BASEDIR; then
    echo "$BASEDIR already present not building image"
    exit 0
fi
mkdir -p $BASEDIR
WORKDIR="$(realpath $BASEDIR)"
IMAGE_NAME=$(echo $CONFIG_FILE | jq -r '.image.name')
SIZE=$(echo $CONFIG_FILE | jq -r '.image.size')

trap "phase4 $WORKDIR error" ERR
trap "phase4 $WORKDIR error" EXIT

phase1 $WORKDIR $IMAGE_NAME $SIZE
phase2 $WORKDIR $LOOP
phase3 $WORKDIR $LOOP

trap - ERR
trap - EXIT
phase4 $WORKDIR normal