Shell script for modify dockerpi image and install there required packages on first boot.

dockerpi-modify.sh

#/bin/bash

#set -x

#ZIP_URL="http://downloads.raspberrypi.org/raspbian_lite/images/raspbian_lite-2015-11-24/2015-11-21-raspbian-jessie-lite.zip"
#ZIP_NAME="2015-11-21-raspbian-jessie-lite.zip"
#IMG_NAME="2015-11-21-raspbian-jessie-lite.img"


ZIP_URL="http://downloads.raspberrypi.org/raspbian_lite/images/raspbian_lite-2019-09-30/2019-09-26-raspbian-buster-lite.zip"
ZIP_NAME="2019-09-26-raspbian-buster-lite.zip"
IMG_NAME="2019-09-26-raspbian-buster-lite.img"


MOUNT_PATH=/opt/pi-mount
LOOP_NAME="/dev/loop0" # get empty loop device
PART_NAME="/dev/loop0p2" # get /dev/loop0p2 by fdisk -l $LOOP_NAME
IMG_NAME_MOD="filesystem.img"

DMPWD=`pwd`

if [ "$EUID" -ne 0 ]
  then echo "Please run with sudo"
  exit
fi

if [ ! -f "$ZIP_NAME" ]
then
  echo "Downloading filesystem image"
  wget $ZIP_URL
fi

if [ ! -f "$IMG_NAME" ]
then
  echo "Unzipping filesystem image"
  unzip $ZIP_NAME
fi

chmod 777 $IMG_NAME $ZIP_NAME

FPARAM=$1
if [[ "$FPARAM" != "--force" ]]
then
  if [ -f "$IMG_NAME_MOD" ]
  then
    echo "$IMG_NAME_MOD file already exists. You can remove it to modify again or call with --force"
    exit 1
  fi
fi

echo "Modifying filesystem image $IMG_NAME"
cp $IMG_NAME $IMG_NAME_MOD

if [ -d "$MOUNT_PATH/bin" ]; then umount $MOUNT_PATH; fi
if [ -f "$LOOP_NAME" ]; then losetup -d $LOOP_NAME; fi
mkdir -p $MOUNT_PATH
chmod 777 $MOUNT_PATH

losetup $LOOP_NAME $IMG_NAME_MOD
partprobe $LOOP_NAME
mount -t ext4 -o rw,sync,nosuid,nodev,relatime,uhelper=udisks2 $PART_NAME $MOUNT_PATH

if [ ! -d "$MOUNT_PATH/bin" ]
then
  echo "Mount failed, exit..."
  if [ -d "$MOUNT_PATH/bin" ]; then umount $MOUNT_PATH; fi
  if [ -f "$LOOP_NAME" ]; then losetup -d $LOOP_NAME; fi
  exit 1
fi

ls -alh $MOUNT_PATH/
if [ -f "$MOUNT_PATH/modified.flag" ]
then
  echo "Already modified, exit..."
  echo "Next step: docker run -it -v \`pwd\`:/sdcard/ lukechilds/dockerpi:vm"
  umount $MOUNT_PATH
  losetup -d $LOOP_NAME
  exit 1
fi

# add service
cat <<EOT >> $MOUNT_PATH/etc/systemd/system/firstboot.service
[Unit]
Description=FirstBoot
After=network.target
Before=rc-local.service
ConditionFileNotEmpty=/firstboot.sh

[Service]
Type=oneshot
#Type=default
ExecStart=/firstboot.sh
#ExecStartPost=/bin/mv /firstboot.sh /firstboot.sh.done
RemainAfterExit=no
StandardOutput=tty
StandardError=tty
SyslogIdentifier=firstboot

[Install]
WantedBy=multi-user.target
EOT

# add script
cat <<EOT >> $MOUNT_PATH/firstboot.sh
#!/bin/bash
#set -x
sleep 15
sudo apt-get update --allow-releaseinfo-change
sudo apt-get install -y build-essential
sudo apt-get autoremove -y
sleep 30
sudo halt
EOT

chmod a+x $MOUNT_PATH/firstboot.sh

cd $MOUNT_PATH/etc/systemd/system/multi-user.target.wants/
ln -s /etc/systemd/system/firstboot.service .

cd $DMPWD
touch $MOUNT_PATH/modified.flag
umount $MOUNT_PATH
losetup -d $LOOP_NAME
sleep 1
rmdir $MOUNT_PATH

echo "Finishing..."
echo "Next step: docker run -it -v \`pwd\`:/sdcard/ lukechilds/dockerpi:vm"