chroot_from_image

#!/bin/bash

source lib/tools.sh

is_run_as_root

if [ $# -lt 1 ]; then
    echo "Usage: $0 <Linux distribution> [Command]"
    echo
    echo "Examples:"
    echo " - $0 ubuntu"
    echo " - $0 alpine /bin/sh"
    exit 1
fi

DISTRO=$1
MOUNT_DIR="distro_chroot/${DISTRO}"
COMMAND=${2:-"/bin/bash"}
DNS_RESOLVER="1.1.1.1"

# Check if docker is installed
if ! command -v docker &> /dev/null; then
    echo "Docker is not installed. Please install Docker first."
    exit 1
fi

container_name_from_image

# Check that the asked image does not already exist as a container
if docker ps -a --format '{{.Names}}' | grep -q "^${CONTAINER_NAME}$"; then
    echo "A container named ${CONTAINER_NAME} already exists. Please remove it first."
    exit 1
else
    # Create a docker container from the asked image
    docker create --name "${CONTAINER_NAME}" "${DISTRO}" "${COMMAND}" > /dev/null
    if [ $? -ne 0 ]; then
        echo "Error during the creation of the container from ${DISTRO} image."
        exit 1
    fi
fi

# Create a directory to store the image filesystem
mkdir -p "${MOUNT_DIR}"
if [ $? -ne 0 ]; then
    echo "Error during the creation of the mount directory."
    exit 1
fi

# Extract the docker image content, mount directories
docker export "${CONTAINER_NAME}" | tar x -C "${MOUNT_DIR}"
if [ $? -ne 0 ]; then
    echo "Error during the extraction of the image content."
    exit 1
fi

# Check the asked command exists in the extracted image
if ! { [ -x "${MOUNT_DIR}/${COMMAND}" ] || [ -x "${MOUNT_DIR}/usr/bin/${COMMAND}" ] || [ -x "${MOUNT_DIR}/usr/sbin/${COMMAND}" ]; }; then
    echo "The command ${COMMAND} does not exist in the extracted image."
    exit 1
fi

# Mount the necessary directories
mount --bind /dev "${MOUNT_DIR}/dev"
mount -t devpts /dev/pts "${MOUNT_DIR}/dev/pts"
mount -t proc /proc "${MOUNT_DIR}/proc"
mount -t sysfs /sys "${MOUNT_DIR}/sys"
echo "nameserver ${DNS_RESOLVER}" > "${MOUNT_DIR}/etc/resolv.conf"

# Chroot into the container, clean after exit
chroot "${MOUNT_DIR}" "${COMMAND}"
trap unmount_and_clean EXIT