rootfs.sh

#!/usr/bin/env bash
#
# Copyright (c) 2018 Intel Corporation
#
# SPDX-License-Identifier: Apache-2.0

set -o errexit
set -o pipefail
set -o errtrace

[ -n "$DEBUG" ] && set -x

script_name="${0##*/}"
script_dir="$(dirname $(readlink -f $0))"
AGENT_VERSION=${AGENT_VERSION:-}
RUST_VERSION="null"
AGENT_BIN=${AGENT_BIN:-kata-agent}
AGENT_INIT=${AGENT_INIT:-no}
MEASURED_ROOTFS=${MEASURED_ROOTFS:-no}
KERNEL_MODULES_DIR=${KERNEL_MODULES_DIR:-""}
OSBUILDER_VERSION="unknown"
DOCKER_RUNTIME=${DOCKER_RUNTIME:-runc}
# this GOPATH is for installing yq from install_yq.sh
export GOPATH=${GOPATH:-${HOME}/go}
LIBC=${LIBC:-musl}
# The kata agent enables seccomp feature.
# However, it is not enforced by default: you need to enable that in the main configuration file.
SECCOMP=${SECCOMP:-"yes"}
SELINUX=${SELINUX:-"no"}
AGENT_POLICY=${AGENT_POLICY:-no}

lib_file="${script_dir}/../scripts/lib.sh"
source "$lib_file"

#For cross build
CROSS_BUILD=${CROSS_BUILD:-false}
BUILDX=""
PLATFORM=""
TARGET_ARCH=${TARGET_ARCH:-$(uname -m)}
ARCH=${ARCH:-$(uname -m)}
[ "${TARGET_ARCH}" == "aarch64" ] && TARGET_ARCH=arm64
TARGET_OS=${TARGET_OS:-linux}
[ "${CROSS_BUILD}" == "true" ] && BUILDX=buildx && PLATFORM="--platform=${TARGET_OS}/${TARGET_ARCH}"

handle_error() {
	local exit_code="${?}"
	local line_number="${1:-}"
	echo "Failed at $line_number: ${BASH_COMMAND}"
	exit "${exit_code}"

}
trap 'handle_error $LINENO' ERR

# Default architecture
export ARCH=${ARCH:-$(uname -m)}
if [ "$ARCH" == "ppc64le" ] || [ "$ARCH" == "s390x" ]; then
	LIBC=gnu
	echo "WARNING: Forcing LIBC=gnu because $ARCH has no musl Rust target"
fi

# distro-specific config file
typeset -r CONFIG_SH="config.sh"

# Name of an optional distro-specific file which, if it exists, must implement the
# build_rootfs() function.
typeset -r LIB_SH="rootfs_lib.sh"

# rootfs distro name specified by the user
typeset distro=

# Absolute path to the rootfs root folder
typeset ROOTFS_DIR

# Absolute path in the rootfs to the "init" executable / symlink.
# Typically something like "${ROOTFS_DIR}/init
typeset init=

#$1: Error code if want to exit different to 0
usage()
{
	error="${1:-0}"
	cat <<EOF

Usage: ${script_name} [options] [DISTRO]

Build and setup a rootfs directory based on DISTRO OS, used to create
Kata Containers images or initramfs.

When no DISTRO is provided, an existing base rootfs at ROOTFS_DIR is provisioned
with the Kata specific components and configuration.

Supported DISTRO values:
$(get_distros | tr "\n" " ")

Options:
  -a <version>      Specify the agent version. Overrides the AGENT_VERSION
                    environment variable.
  -h                Show this help message.
  -l                List the supported Linux distributions and exit immediately.
  -o <version>      Specify the version of osbuilder to embed in the rootfs
                    yaml description.
  -r <directory>    Specify the rootfs base directory. Overrides the ROOTFS_DIR
                    environment variable.
  -t DISTRO         Print the test configuration for DISTRO and exit
                    immediately.

Environment Variables:
AGENT_BIN           Name of the agent binary (used when running sanity checks on
                    the rootfs).
                    Default value: ${AGENT_BIN}

AGENT_INIT          When set to "yes", use ${AGENT_BIN} as init process in place
                    of systemd.
                    Default value: no

AGENT_SOURCE_BIN    Path to the directory of agent binary.
                    If set, use the binary as agent but not build agent package.
                    Default value: <not set>

AGENT_VERSION       Version of the agent to include in the rootfs.
                    Default value: ${AGENT_VERSION:-<not set>}

ARCH                Target architecture (according to \`uname -m\`).
                    Foreign bootstraps are currently only supported for Ubuntu
                    and glibc agents.
                    Default value: $(uname -m)

DISTRO_REPO         Use host repositories to install guest packages.
                    Default value: <not set>

DOCKER_RUNTIME      Docker runtime to use when USE_DOCKER is set.
                    Default value: runc

GRACEFUL_EXIT       If set, and if the DISTRO configuration specifies a
                    non-empty BUILD_CAN_FAIL variable, do not return with an
                    error code in case any of the build step fails.
                    This is used when running CI jobs, to tolerate failures for
                    specific distributions.
                    Default value: <not set>

IMAGE_REGISTRY      Hostname for the image registry used to pull down the rootfs
                    build image.
                    Default value: docker.io

KERNEL_MODULES_DIR  Path to a directory containing kernel modules to include in
                    the rootfs.
                    Default value: <empty>

LIBC                libc the agent is built against (gnu or musl).
                    Default value: ${LIBC} (varies with architecture)

ROOTFS_DIR          Path to the directory that is populated with the rootfs.
                    Default value: <${script_name} path>/rootfs-<DISTRO-name>

SECCOMP             When set to "no", the kata-agent is built without seccomp capability.
                    Default value: "yes"

SELINUX             When set to "yes", build the rootfs with the required packages to
                    enable SELinux in the VM.
                    Make sure the guest kernel is compiled with SELinux enabled.
                    Default value: "no"

USE_DOCKER          If set, build the rootfs inside a container (requires
                    Docker).
                    Default value: <not set>

USE_PODMAN          If set and USE_DOCKER not set, then build the rootfs inside
                    a podman container (requires podman).
                    Default value: <not set>

Refer to the Platform-OS Compatibility Matrix for more details on the supported
architectures:
https://github.com/kata-containers/kata-containers/tree/main/tools/osbuilder#platform-distro-compatibility-matrix

EOF
exit "${error}"
}

get_distros() {
	cdirs=$(find "${script_dir}" -maxdepth 1 -type d)
	find ${cdirs} -maxdepth 1 -name "${CONFIG_SH}" -printf '%H\n' | while read dir; do
		basename "${dir}"
	done
}

get_test_config() {
	local -r distro="$1"
	[ -z "$distro" ] && die "No distro name specified"

	local config="${script_dir}/${distro}/config.sh"
	source ${config}

	echo -e "INIT_PROCESS:\t\t$INIT_PROCESS"
	echo -e "ARCH_EXCLUDE_LIST:\t\t${ARCH_EXCLUDE_LIST[@]}"
}

check_function_exist()
{
	function_name="$1"
	[ "$(type -t ${function_name})" == "function" ] || die "${function_name} function was not defined"
}

docker_extra_args()
{
	local args=""

	# Required to mount inside a container
	args+=" --cap-add SYS_ADMIN"
	# Requred to chroot
	args+=" --cap-add SYS_CHROOT"
	# debootstrap needs to create device nodes to properly function
	args+=" --cap-add MKNOD"

	case "$1" in
	gentoo)
		# Required to build glibc
		args+=" --cap-add SYS_PTRACE"
		# mount portage volume
		args+=" -v ${gentoo_local_portage_dir}:/usr/portage/packages"
		args+=" --volumes-from ${gentoo_portage_container}"
		;;
	debian | ubuntu | suse)
		source /etc/os-release

		case "$ID" in
		fedora | centos | rhel)
			# Depending on the podman version, we'll face issues when passing
		        # `--security-opt apparmor=unconfined` on a system where not apparmor is not installed.
			# Because of this, let's just avoid adding this option when the host OS comes from Red Hat.

			# A explict check for podman, at least for now, can be avoided.
			;;
		*)
			# When AppArmor is enabled, mounting inside a container is blocked with docker-default profile.
			# See https://github.com/moby/moby/issues/16429
			args+=" --security-opt apparmor=unconfined"
			;;
		esac
		;;
	*)
		;;
	esac

	echo "$args"
}

setup_agent_init()
{
	agent_bin="$1"
	init_bin="$2"

	[ -z "$agent_bin" ] && die "need agent binary path"
	[ -z "$init_bin" ] && die "need init bin path"

	info "Install $agent_bin as init process"
	mv -f "${agent_bin}" ${init_bin}
	OK "Agent is installed as init process"
}

copy_kernel_modules()
{
	local module_dir="$1"
	local rootfs_dir="$2"

	[ -z "$module_dir" ] && die "need module directory"
	[ -z "$rootfs_dir" ] && die "need rootfs directory"

	local dest_dir="${rootfs_dir}/lib/modules"

	info "Copy kernel modules from ${KERNEL_MODULES_DIR}"
	mkdir -p "${dest_dir}"
	cp -a "${KERNEL_MODULES_DIR}" "${dest_dir}/"
	OK "Kernel modules copied"
}

error_handler()
{
	[ "$?" -eq 0 ] && return

	if [ -n "$GRACEFUL_EXIT" ] && [ -n "$BUILD_CAN_FAIL" ]; then
		info "Detected a build error, but $distro is allowed to fail (BUILD_CAN_FAIL specified), so exiting sucessfully"
		touch "$(dirname ${ROOTFS_DIR})/${distro}_fail"
		exit 0
	fi
}

# Compares two SEMVER-style versions passed as arguments, up to the MINOR version
# number.
# Returns a zero exit code if the version specified by the first argument is
# older OR equal than / to the version in the second argument, non-zero exit
# code otherwise.
compare_versions()
{
	typeset -i -a v1=($(echo "$1" | awk 'BEGIN {FS = "."} {print $1" "$2}'))
	typeset -i -a v2=($(echo "$2" | awk 'BEGIN {FS = "."} {print $1" "$2}'))

	# Sanity check: first version can't be all zero
	[ "${v1[0]}" -eq "0" ] && \
		[ "${v1[1]}" -eq "0" ] && \
		die "Failed to parse version number"

	# Major
	[ "${v1[0]}" -gt "${v2[0]}" ] && { false; return; }

	# Minor
	[ "${v1[0]}" -eq "${v2[0]}" ] && \
		[ "${v1[1]}" -gt "${v2[1]}" ] && { false; return; }

	true
}

check_env_variables()
{
	# this will be mounted to container for using yq on the host side.
	GOPATH_LOCAL="${GOPATH%%:*}"

	[ "$AGENT_INIT" == "yes" -o "$AGENT_INIT" == "no" ] || die "AGENT_INIT($AGENT_INIT) is invalid (must be yes or no)"
	[ "$AGENT_POLICY" == "yes" -o "$AGENT_POLICY" == "no" ] || die "AGENT_POLICY($AGENT_POLICY) is invalid (must be yes or no)"

	[ -n "${KERNEL_MODULES_DIR}" ] && [ ! -d "${KERNEL_MODULES_DIR}" ] && die "KERNEL_MODULES_DIR defined but is not an existing directory"

	[ -n "${OSBUILDER_VERSION}" ] || die "need osbuilder version"
}

# Builds a rootfs based on the distro name provided as argument
build_rootfs_distro()
{
	repo_dir="${script_dir}/../../../"
	[ -n "${distro}" ] || usage 1
	distro_config_dir="${script_dir}/${distro}"

	[ -d "${distro_config_dir}" ] || die "Not found configuration directory ${distro_config_dir}"

	# Source config.sh from distro
	rootfs_config="${distro_config_dir}/${CONFIG_SH}"
	source "${rootfs_config}"

	if [ -z "$ROOTFS_DIR" ]; then
		 ROOTFS_DIR="${script_dir}/rootfs-${OS_NAME}"
	fi

	if [ -e "${distro_config_dir}/${LIB_SH}" ];then
		rootfs_lib="${distro_config_dir}/${LIB_SH}"
		info "rootfs_lib.sh file found. Loading content"
		source "${rootfs_lib}"
	fi

	CONFIG_DIR=${distro_config_dir}
	check_function_exist "build_rootfs"

	if [ -z "$INSIDE_CONTAINER" ] ; then
		# Capture errors, but only outside of the docker container
		trap error_handler ERR
	fi

	if [ -d "${ROOTFS_DIR}" ] && [ "${ROOTFS_DIR}" != "/" ]; then
		rm -rf "${ROOTFS_DIR}"/*
	else
		mkdir -p ${ROOTFS_DIR}
	fi

	# need to detect rustc's version too?
	detect_rust_version ||
		die "Could not detect the required rust version for AGENT_VERSION='${AGENT_VERSION:-main}'."

	echo "Required rust version: $RUST_VERSION"

	if [ "${SELINUX}" == "yes" ]; then
		if [ "${AGENT_INIT}" == "yes" ]; then
			die "Guest SELinux with the agent init is not supported yet"
		fi
		if [ "${distro}" != "centos" ]; then
			die "The guest rootfs must be CentOS to enable guest SELinux"
		fi
	fi

	if [ -z "${USE_DOCKER}" ] && [ -z "${USE_PODMAN}" ]; then
		info "build directly"
		build_rootfs ${ROOTFS_DIR}
	else
		engine_build_args=""
		if [ -n "${USE_DOCKER}" ]; then
			container_engine="docker"
		elif [ -n "${USE_PODMAN}" ]; then
			container_engine="podman"
			engine_build_args+=" --runtime ${DOCKER_RUNTIME}"
		fi

		image_name="${distro}-rootfs-osbuilder"

		if [ -n "${IMAGE_REGISTRY}" ]; then
			engine_build_args+=" --build-arg IMAGE_REGISTRY=${IMAGE_REGISTRY}"
		fi

		# setup to install rust here
		generate_dockerfile "${distro_config_dir}"
		"$container_engine" build  \
			${engine_build_args} \
			--build-arg http_proxy="${http_proxy}" \
			--build-arg https_proxy="${https_proxy}" \
			-t "${image_name}" "${distro_config_dir}"

		# fake mapping if KERNEL_MODULES_DIR is unset
		kernel_mod_dir=${KERNEL_MODULES_DIR:-${ROOTFS_DIR}}

		engine_run_args=""
		engine_run_args+=" --rm"
		# apt sync scans all possible fds in order to close them, incredibly slow on VMs
		engine_run_args+=" --ulimit nofile=262144:262144"
		engine_run_args+=" --runtime ${DOCKER_RUNTIME}"

		if [ -z "${AGENT_SOURCE_BIN}" ] ; then
			engine_run_args+=" -v ${GOPATH_LOCAL}:${GOPATH_LOCAL} --env GOPATH=${GOPATH_LOCAL}"
		else
			engine_run_args+=" --env AGENT_SOURCE_BIN=${AGENT_SOURCE_BIN}"
			engine_run_args+=" -v ${AGENT_SOURCE_BIN}:${AGENT_SOURCE_BIN}"
			engine_run_args+=" -v ${GOPATH_LOCAL}:${GOPATH_LOCAL} --env GOPATH=${GOPATH_LOCAL}"
		fi

		engine_run_args+=" $(docker_extra_args $distro)"

		# Relabel volumes so SELinux allows access (see docker-run(1))
		if command -v selinuxenabled > /dev/null && selinuxenabled ; then
			SRC_VOL=("${GOPATH_LOCAL}")

			for volume_dir in "${script_dir}" \
					  "${ROOTFS_DIR}" \
					  "${script_dir}/../scripts" \
					  "${kernel_mod_dir}" \
					  "${SRC_VOL[@]}"; do
				chcon -Rt svirt_sandbox_file_t "$volume_dir"
			done
		fi

		before_starting_container
		trap after_stopping_container EXIT

		#Make sure we use a compatible runtime to build rootfs
		# In case Clear Containers Runtime is installed we dont want to hit issue:
		#https://github.com/clearcontainers/runtime/issues/828
		"$container_engine" run  \
			--env https_proxy="${https_proxy}" \
			--env http_proxy="${http_proxy}" \
			--env AGENT_VERSION="${AGENT_VERSION}" \
			--env ROOTFS_DIR="/rootfs" \
			--env AGENT_BIN="${AGENT_BIN}" \
			--env AGENT_INIT="${AGENT_INIT}" \
			--env ARCH="${ARCH}" \
			--env CI="${CI}" \
			--env MEASURED_ROOTFS="${MEASURED_ROOTFS}" \
			--env KERNEL_MODULES_DIR="${KERNEL_MODULES_DIR}" \
			--env LIBC="${LIBC}" \
			--env EXTRA_PKGS="${EXTRA_PKGS}" \
			--env OSBUILDER_VERSION="${OSBUILDER_VERSION}" \
			--env OS_VERSION="${OS_VERSION}" \
			--env INSIDE_CONTAINER=1 \
			--env SECCOMP="${SECCOMP}" \
			--env SELINUX="${SELINUX}" \
			--env DEBUG="${DEBUG}" \
			--env HOME="/root" \
			--env AGENT_POLICY="${AGENT_POLICY}" \
			-v "${repo_dir}":"/kata-containers" \
			-v "${ROOTFS_DIR}":"/rootfs" \
			-v "${script_dir}/../scripts":"/scripts" \
			-v "${kernel_mod_dir}":"${kernel_mod_dir}" \
			$engine_run_args \
			${image_name} \
			bash /kata-containers/tools/osbuilder/rootfs-builder/rootfs.sh "${distro}"

		exit $?
	fi
}

# Used to create a minimal directory tree where the agent can be installed.
# This is used when a distro is not specified.
prepare_overlay()
{
	pushd "${ROOTFS_DIR}" > /dev/null
	mkdir -p ./etc ./lib/systemd ./sbin ./var

	# This symlink hacking is mostly to make later rootfs
	# validation work correctly for the dracut case.
	# We skip this if /sbin/init exists in the rootfs, meaning
	# we were passed a pre-populated rootfs directory
	if [ ! -e ./sbin/init ]; then
		ln -sf  ./usr/lib/systemd/systemd ./init
		ln -sf  /init ./sbin/init
	fi

	popd  > /dev/null
}

# Setup an existing rootfs directory, based on the OPTIONAL distro name
# provided as argument
setup_rootfs()
{
	info "Create symlink to /tmp in /var to create private temporal directories with systemd"
	pushd "${ROOTFS_DIR}" >> /dev/null
	if [ "$PWD" != "/" ] ; then
		rm -rf ./var/cache/ ./var/lib ./var/log ./var/tmp
	fi

	ln -s ../tmp ./var/

	# For some distros tmp.mount may not be installed by default in systemd paths
	if ! [ -f "./etc/systemd/system/tmp.mount" ] && \
		! [ -f "./usr/lib/systemd/system/tmp.mount" ] &&
		[ "$AGENT_INIT" != "yes" ]; then
		local unitFile="./etc/systemd/system/tmp.mount"
		info "Install tmp.mount in ./etc/systemd/system"
		mkdir -p `dirname "$unitFile"`
		cp ./usr/share/systemd/tmp.mount "$unitFile" || cat > "$unitFile" << EOF
#  This file is part of systemd.
#
#  systemd is free software; you can redistribute it and/or modify it
#  under the terms of the GNU Lesser General Public License as published by
#  the Free Software Foundation; either version 2.1 of the License, or
#  (at your option) any later version.

[Unit]
Description=Temporary Directory (/tmp)
Documentation=man:hier(7)
Documentation=https://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
ConditionPathIsSymbolicLink=!/tmp
DefaultDependencies=no
Conflicts=umount.target
Before=local-fs.target umount.target
After=swap.target

[Mount]
What=tmpfs
Where=/tmp
Type=tmpfs
Options=mode=1777,strictatime,nosuid,nodev
EOF
	fi

	popd  >> /dev/null

	[ -n "${KERNEL_MODULES_DIR}" ] && copy_kernel_modules ${KERNEL_MODULES_DIR} ${ROOTFS_DIR}

	info "Create ${ROOTFS_DIR}/etc"
	mkdir -p "${ROOTFS_DIR}/etc"

	case "${distro}" in
		"ubuntu" | "debian")
			echo "I am ubuntu or debian"
			chrony_conf_file="${ROOTFS_DIR}/etc/chrony/chrony.conf"
			chrony_systemd_service="${ROOTFS_DIR}/lib/systemd/system/chrony.service"
			;;
		"ubuntu")
			# Fix for #4932 - Boot hang at: "A start job is running for /dev/ttyS0"
			mkdir -p "${ROOTFS_DIR}/etc/systemd/system/getty.target.wants"
			ln -sf "/lib/systemd/system/getty@.service" "${ROOTFS_DIR}/etc/systemd/system/getty.target.wants/getty@ttyS0.service"
			;;
		*)
			chrony_conf_file="${ROOTFS_DIR}/etc/chrony.conf"
			chrony_systemd_service="${ROOTFS_DIR}/usr/lib/systemd/system/chronyd.service"
			;;
	esac

	info "Configure chrony file ${chrony_conf_file}"
	cat >> "${chrony_conf_file}" <<EOF
refclock PHC /dev/ptp0 poll 3 dpoll -2 offset 0
# Step the system clock instead of slewing it if the adjustment is larger than
# one second, at any time
makestep 1 -1
EOF

	# Comment out ntp sources for chrony to be extra careful
	# Reference:  https://chrony.tuxfamily.org/doc/3.4/chrony.conf.html
	sed -i 's/^\(server \|pool \|peer \)/# &/g'  ${chrony_conf_file}

	if [ -f "$chrony_systemd_service" ]; then
		# Remove user option, user could not exist in the rootfs
		# Set the /var/lib/chrony for ReadWritePaths to be ignored if
		# its nonexistent, this broke the service on boot previously
		# due to the directory not being present "(code=exited, status=226/NAMESPACE)"
		sed -i -e 's/^\(ExecStart=.*\)-u [[:alnum:]]*/\1/g' \
		       -e '/^\[Unit\]/a ConditionPathExists=\/dev\/ptp0' \
		       -e 's/^ReadWritePaths=\(.\+\) \/var\/lib\/chrony \(.\+\)$/ReadWritePaths=\1 -\/var\/lib\/chrony \2/m' \
		       ${chrony_systemd_service}
	fi

	AGENT_DIR="${ROOTFS_DIR}/usr/bin"
	AGENT_DEST="${AGENT_DIR}/${AGENT_BIN}"

	if [ -z "${AGENT_SOURCE_BIN}" ] ; then
		test -r "${HOME}/.cargo/env" && source "${HOME}/.cargo/env"
		# rust agent needs ${arch}-unknown-linux-${LIBC}
		if ! (rustup show | grep -v linux-${LIBC} > /dev/null); then
			if [ "$RUST_VERSION" == "null" ]; then
				detect_rust_version || \
					die "Could not detect the required rust version for AGENT_VERSION='${AGENT_VERSION:-main}'."
			fi
			bash ${script_dir}/../../../ci/install_rust.sh ${RUST_VERSION}
		fi
		test -r "${HOME}/.cargo/env" && source "${HOME}/.cargo/env"

		agent_dir="${script_dir}/../../../src/agent/"

		if [ "${SECCOMP}" == "yes" ]; then
			info "Set up libseccomp"
			detect_libseccomp_info || \
				die "Could not detect the required libseccomp version and url"
			export libseccomp_install_dir=$(mktemp -d -t libseccomp.XXXXXXXXXX)
			export gperf_install_dir=$(mktemp -d -t gperf.XXXXXXXXXX)
			${script_dir}/../../../ci/install_libseccomp.sh "${libseccomp_install_dir}" "${gperf_install_dir}"
			echo "Set environment variables for the libseccomp crate to link the libseccomp library statically"
			export LIBSECCOMP_LINK_TYPE=static
			export LIBSECCOMP_LIB_PATH="${libseccomp_install_dir}/lib"
		fi

		info "Build agent"
		pushd "${agent_dir}"
		if [ -n "${AGENT_VERSION}" ]; then
			git checkout "${AGENT_VERSION}" && OK "git checkout successful" || die "checkout agent ${AGENT_VERSION} failed!"
		fi
		make clean
		make LIBC=${LIBC} INIT=${AGENT_INIT} SECCOMP=${SECCOMP} AGENT_POLICY=${AGENT_POLICY}
		make install DESTDIR="${ROOTFS_DIR}" LIBC=${LIBC} INIT=${AGENT_INIT}
		strip ${ROOTFS_DIR}/usr/bin/kata-agent
		if [ "${SECCOMP}" == "yes" ]; then
			rm -rf "${libseccomp_install_dir}" "${gperf_install_dir}"
		fi
		popd
	else
		mkdir -p ${AGENT_DIR}
		cp ${AGENT_SOURCE_BIN} ${AGENT_DEST}
		OK "cp ${AGENT_SOURCE_BIN} ${AGENT_DEST}"
	fi

	[ -x "${AGENT_DEST}" ] || die "${AGENT_DEST} is not installed in ${ROOTFS_DIR}"
	OK "Agent installed"

	if [ "${AGENT_INIT}" == "yes" ]; then
		setup_agent_init "${AGENT_DEST}" "${init}"
	else
		# Setup systemd-based environment for kata-agent
		mkdir -p "${ROOTFS_DIR}/etc/systemd/system/basic.target.wants"
		ln -sf "/usr/lib/systemd/system/kata-containers.target" "${ROOTFS_DIR}/etc/systemd/system/basic.target.wants/kata-containers.target"
		mkdir -p "${ROOTFS_DIR}/etc/systemd/system/kata-containers.target.wants"
		ln -sf "/usr/lib/systemd/system/dbus.socket" "${ROOTFS_DIR}/etc/systemd/system/kata-containers.target.wants/dbus.socket"
		chmod g+rx,o+x "${ROOTFS_DIR}"
	fi

	if [ "${AGENT_POLICY}" == "yes" ]; then
		# Setup systemd-based environment for kata-opa.
		local opa_bin_dir="$(get_opa_bin_dir "${ROOTFS_DIR}")"
		if [ -z "${opa_bin_dir}" ]; then
			# OPA was not installed already, so download it here.
			#
			# TODO: if an OPA package is not available for the Guest image distro,
			#   	Kata should cache the OPA source code, toolchain information, etc.
			#   	OPA should be built from the cached source code instead of downloading
			#   	this binary.
			#
			opa_bin_url="$(get_package_version_from_kata_yaml externals.open-policy-agent.meta.binary)"
			info "Downloading OPA binary from ${opa_bin_url}"
			curl --fail -L "${opa_bin_url}" -o opa || die "Failed to download OPA"

			# Install the OPA binary.
			opa_bin_dir="/usr/local/bin"
			local opa_bin="${ROOTFS_DIR}${opa_bin_dir}/opa"
			info "Installing OPA binary to ${opa_bin}"
			install -D -o root -g root -m 0755 opa -T "${opa_bin}"
			strip ${ROOTFS_DIR}${opa_bin_dir}/opa
		else
			info "OPA binary already exists in ${opa_bin_dir}"
		fi

		# Install default settings for the kata-opa service.
		local kata_opa_in_dir="${script_dir}/../../../src/kata-opa"
		local opa_settings_dir="/etc/kata-opa"
		local policy_file="allow-all.rego"
		local policy_dir="${ROOTFS_DIR}/${opa_settings_dir}"
		mkdir -p "${policy_dir}"
		install -D -o root -g root -m 0644 "${kata_opa_in_dir}/${policy_file}" -T "${policy_dir}/${policy_file}"
		ln -sf "${policy_file}" "${policy_dir}/default-policy.rego"

		if [ "${AGENT_INIT}" == "yes" ]; then
			info "OPA will be started by the kata agent"
		else
			# Install the unit file for the kata-opa service.
			local kata_opa_unit="kata-opa.service"
			local kata_opa_unit_path="${ROOTFS_DIR}/usr/lib/systemd/system/${kata_opa_unit}"
			local kata_containers_wants="${ROOTFS_DIR}/etc/systemd/system/kata-containers.target.wants"

			opa_settings_dir="${opa_settings_dir//\//\\/}"
			sed -e "s/@SETTINGSDIR@/${opa_settings_dir}/g" "${kata_opa_in_dir}/${kata_opa_unit}.in" > "${kata_opa_unit}"

			opa_bin_dir="${opa_bin_dir//\//\\/}"
			sed -i -e "s/@BINDIR@/${opa_bin_dir}/g" "${kata_opa_unit}"

			install -D -o root -g root -m 0644 "${kata_opa_unit}" -T "${kata_opa_unit_path}"
			mkdir -p "${kata_containers_wants}"
			ln -sf "${kata_opa_unit_path}" "${kata_containers_wants}/${kata_opa_unit}"
		fi
	fi

	info "Check init is installed"
	[ -x "${init}" ] || [ -L "${init}" ] || die "/sbin/init is not installed in ${ROOTFS_DIR}"
	OK "init is installed"

	# Create an empty /etc/resolv.conf, to allow agent to bind mount container resolv.conf to Kata VM
	dns_file="${ROOTFS_DIR}/etc/resolv.conf"
	if [ -L "$dns_file" ]; then
		# if /etc/resolv.conf is a link, it cannot be used for bind mount
		rm -f "$dns_file"
	fi
	info "Create /etc/resolv.conf file in rootfs if not exist"
	touch "$dns_file"

	info "Creating summary file"
	create_summary_file "${ROOTFS_DIR}"
}

get_opa_bin_dir()
{
	local rootfs_dir="$1"
	local -a bin_dirs=(
		"/bin"
		"/usr/bin"
		"/usr/local/bin"
	)
	for bin_dir in "${bin_dirs[@]}"
	do
		local opa_bin="${rootfs_dir}${bin_dir}/opa"
		if [ -f "${opa_bin}" ]; then
			echo "${bin_dir}"
			return 0
		fi
	done
}

parse_arguments()
{
	[ "$#" -eq 0 ] && usage && return 0

	while getopts a:hlo:r:t: opt
	do
		case $opt in
			a)	AGENT_VERSION="${OPTARG}" ;;
			h)	usage ;;
			l)	get_distros | sort && exit 0;;
			o)	OSBUILDER_VERSION="${OPTARG}" ;;
			r)	ROOTFS_DIR="${OPTARG}" ;;
			t)	get_test_config "${OPTARG}" && exit 0;;
			*)  die "Found an invalid option";;
		esac
	done

	shift $(($OPTIND - 1))
	distro="$1"
	arch=$(uname -m)
}

detect_host_distro()
{
	source /etc/os-release

	case "$ID" in
		"*suse*")
			distro="suse"
			;;
		"clear-linux-os")
			distro="clearlinux"
			;;
		*)
			distro="$ID"
			;;
	esac
}

main()
{
	parse_arguments $*
	check_env_variables

	if [ -n "$distro" ]; then
		build_rootfs_distro
	else
		#Make sure ROOTFS_DIR is set correctly
		[ -d "${ROOTFS_DIR}" ] || die "Invalid rootfs directory: '$ROOTFS_DIR'"

		# Set the distro for dracut build method
		detect_host_distro
		prepare_overlay
	fi

	init="${ROOTFS_DIR}/sbin/init"
	setup_rootfs
}

main $*