distrobox-init

#!/bin/sh
# POSIX
# Expected env variables:
#	HOME
#	USER

trap '[ "$?" -ne 0 ] && echo An error occurred' EXIT

# Defaults
verbose=0

# Print usage to stdout.
# Arguments:
#   None
# Outputs:
#   print usage with examples.
show_help() {
	echo "USAGE:
	distrobox-init --name $USER --user $(id -ru) --group $(id -rg) --home $HOME

	Arguments:
		--name/-n:		user name
		--user/-u:		uid of the user
		--group/-g:		gid of the user
		--home/-d:		path/to/home of the user
		--help/-h:		show this message
		-v:			show more verbosity
	"
}

# Parse arguments
while :; do
	case $1 in
	-h | --help)
		# Call a "show_help" function to display a synopsis, then exit.
		show_help
		exit
		;;
	-v)
		shift
		verbose=1
		;;
	-n | --name)
		if [ -n "$2" ]; then
			container_user_name="$2"
			shift
			shift
		fi
		;;
	-d | --home)
		if [ -n "$2" ]; then
			container_user_home="$2"
			shift
			shift
		fi
		;;
	-u | --user)
		if [ -n "$2" ]; then
			container_user_uid="$2"
			shift
			shift
		fi
		;;
	-g | --group)
		if [ -n "$2" ]; then
			container_user_gid="$2"
			shift
			shift
		fi
		;;
	*) # Default case: If no more options then break out of the loop.
		break ;;
	esac
done

# Ensure the foundamental variables are set and not empty, we will not proceed if
# they are not all set.
[ -z "${container_user_name}" ] && echo "Invalid arguments, missing username" && exit 1
[ -z "${container_user_uid}" ] && echo "Invalid arguments, missing user uid" && exit 1
[ -z "${container_user_gid}" ] && echo "Invalid arguments, missing user gud" && exit 1
[ -z "${container_user_home}" ] && echo "Invalid argument, missing user home" && exit 1

# Also check we're running inside a container and not on the host
if [ ! -f /run/.containerenv ]; then
	echo "You must run $(basename "$0") inside a container..."
	exit 1
fi

set -o errexit
set -o nounset
# set verbosity
if [ "${verbose}" -ne 0 ]; then
	set -o xtrace
fi

# Bind mount or error.
# Arguments:
#   source_dir
#	target_dir
#	mount_flags -> optional
# Outputs:
#   No output if all ok
#	Error if not
mount_bind() (
	source_dir="$1"
	target_dir="$2"
	mount_flags="$3"
	mount_o=""

	# if source dir doesn't exist, just exit normally
	! [ -d "${source_dir}" ] && ! [ -f "${source_dir}" ] && return 0

	# if the source_dir exists, then create the target_dir
	if [ -d "${source_dir}" ]; then
		# exit if not successful
		if ! mkdir -p "${target_dir}"; then
			echo "Cannot create mount target directory: ${target_dir}"
			return 1
		fi
	elif [ -f "${source_dir}" ]; then
		# exit if not successful
		if ! touch "${target_dir}"; then
			echo "Cannot create mount target file: ${target_dir}"
			return 1
		fi
	fi

	# Add mountflags if needed
	[ "${mount_flags}" = "" ] || mount_o="-o ${mount_flags}"
	# bind mount source_dir to target_dir, return error if not successful
	if ! mount --rbind ${mount_o} "${source_dir}" "${target_dir}"; then
		echo "Failed to bind mount ${source_dir} to ${target_dir}"
		return 1
	fi

	return 0
)

# Return sudoers groups.
# Arguments:
#   None
# Outputs:
#   return all sudoers groups, error if not present.
list_sudo_groups() (
	group=""
	if grep -q "sudo:" /etc/group; then
		group="sudo"
	elif grep -q "wheel:" /etc/group; then
		group="wheel"
	else
		# No group for root, create one
		groupadd wheel
		group="wheel"
	fi

	echo "${group}"
	return 0
)

# We will use host's dynamic config for some functionalities, ensure they are
# symlinks to host's file inside the container.
#
# We do this before checking dependencies, as network access will be needed to
# install them if not found.
HOST_LINKS="/etc/host.conf /etc/hosts /etc/resolv.conf /etc/localtime /etc/timezone"
for link in $HOST_LINKS; do
	rm -f "${link}"
	ln -s /run/host"${link}" "${link}"
done

shell_pkg="$(basename "${SHELL}")"
# Check if dependencies are met for the script to run.
if ! command -v mount || ! command -v passwd ||
	! command -v sudo || ! command -v useradd ||
	! command -v usermod || ! command -v "${shell_pkg}"; then

	# check which pkg manager we have at disposal
	# and make sure we have all the dependencies we need to function.
	if command -v apk; then
		apk add --no-cache sudo shadow procps util-linux "${shell_pkg}"
	elif command -v apt-get; then
		apt-get update && apt-get install -y --no-install-recommends sudo apt-utils passwd procps util-linux "${shell_pkg}"
	elif command -v dnf; then
		dnf install -y --setopt=install_weak_deps=False sudo shadow-utils passwd procps-ng util-linux "${shell_pkg}"
	elif command -v pacman; then
		pacman -Sy --noconfirm sudo procps-ng shadow util-linux "${shell_pkg}"
	elif command -v yum; then
		yum install -y --setopt=install_weak_deps=False sudo shadow-utils passwd procps util-linux "${shell_pkg}"
	elif command -v zypper; then
		zypper install -y --no-recommends sudo shadow procps util-linux "${shell_pkg}"
	else
		echo "FAILED TO INSTALL BASE DEPENDENCIES"
		# Exit as command not found
		exit 127
	fi

fi

# We'll also bind mount in READ-ONLY useful folders from the host
HOST_MOUNTS_RO="/etc/machine-id /var/lib/flatpak /var/lib/systemd/coredump /var/log/journal"
for mount_ro in $HOST_MOUNTS_RO; do
	mount_bind /run/host"${mount_ro}" "${mount_ro}" ro
done

# We'll also bind mount READ-WRITE useful mountpoints to pass external drives and libvirt from
# the host to the container
HOST_MOUNTS="/media /mnt /run/systemd/journal /run/libvirt /var/mnt /var/lib/libvirt"
for mount in $HOST_MOUNTS; do
	mount_bind /run/host"${mount}" "${mount}" rw
done

# If not present, mount host's theme folder in ~/.themes
if mkdir -p "${container_user_home}/.themes/"; then
	if ! ln -s /run/host/usr/share/themes/* "${container_user_home}/.themes/"; then
		echo "Error: cannot link container's themes to host home."
	fi
fi
# If not present, mount host's icons folder in ~/.themes
if mkdir -p "${container_user_home}/.icons/"; then
	if ! ln -s /run/host/usr/share/icons/* "${container_user_home}/.icons/"; then
		echo "Error: cannot link container's icons to host home."
	fi
fi

# Ensure passwordless sudo is set up for user
echo "Defaults !fqdn" >>/etc/sudoers
echo "${container_user_name} ALL = (root) NOPASSWD:ALL" >>/etc/sudoers

# Let's add our user to the container
# if the user already exists, just add it to the sudoers groups
if ! useradd \
	--home-dir "${container_user_home}" \
	--no-create-home \
	--shell /bin/bash \
	--uid "${container_user_uid}" \
	--gid "${container_user_gid}" \
	--groups "$(list_sudo_groups)" \
	"${container_user_name}"; then

	usermod -aG "$(list_sudo_groups)" "${container_user_name}"
fi
# Delete password for root and user
passwd --delete "${container_user_name}"
passwd --delete root

echo "container_setup_done"
# Keepalive loop
sleep infinity