distrobox-init

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

trap '[ "$?" -ne 0 ] && printf "An error occurred\n"' EXIT

# Defaults
verbose=0
version="distrobox_version_placeholder"

# Print usage to stdout.
# Arguments:
#   None
# Outputs:
#   print usage with examples.
show_help() {
	cat <<EOF

distrobox version: ${version}

distrobox-init is the entrypoint of a created distrobox.
Note that this HAS to run from inside a distrobox, will not work if you run it
from your host.

distrobox-init will take care of installing missing dependencies (eg. sudo), set
up the user and groups, mount directories from the host to ensure the tight
integration.

Usage:

	distrobox-init --name ${USER} --user $(id -ru) --group $(id -rg) --home ${HOME}

Options:
	--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
	--verbose/-v:		show more verbosity
	--version/-V:		show version
EOF
}

# Parse arguments
while :; do
	case $1 in
	-h | --help)
		# Call a "show_help" function to display a synopsis, then exit.
		show_help
		exit 0
		;;
	-v | --verbose)
		shift
		verbose=1
		;;
	-V | --version)
		printf "distrobox: %s\n" "${version}"
		exit 0
		;;
	-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

# Also check we're running inside a container and not on the host
if [ ! -f /run/.containerenv ]; then
	printf >&2 "You must run %s inside a container!\n" " $(basename "$0")"
	printf >&2 "distrobox-init should only be used as an entrypoint for a distrobox!\n"
	exit 126
fi

# Ensure the foundamental variables are set and not empty, we will not proceed if
# they are not all set.
[ -z "${container_user_name}" ] && printf >&2 "Invalid arguments, missing username\n" && exit 2
[ -z "${container_user_uid}" ] && printf >&2 "Invalid arguments, missing user uid\n" && exit 2
[ -z "${container_user_gid}" ] && printf >&2 "Invalid arguments, missing user gud\n" && exit 2
[ -z "${container_user_home}" ] && printf >&2 "Invalid argument, missing user home\n" && exit 2

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
			printf >&2 "Cannot create mount target directory: %s\n" "${target_dir}"
			return 1
		fi
	elif [ -f "${source_dir}" ]; then
		# exit if not successful
		if ! touch "${target_dir}"; then
			printf >&2 "Cannot create mount target file: %s\n" "${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
	# shellcheck disable=SC2086
	if ! mount --rbind ${mount_o} "${source_dir}" "${target_dir}"; then
		printf >&2 "Failed to bind mount %s to %s\n" "${source_dir}" "${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

	printf "%s" "${group}"
	return 0
)

# Extract shell name from the $SHELL environment variable
# If not present as package in the container, we want to install it.
shell_pkg="$(basename "${SHELL:-"bash"}")"
# Check if dependencies are met for the script to run.
if ! command -v mount || ! command -v passwd ||
	! command -v sudo || ! command -v useradd ||
	! command -v usermod || ! command -v "${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 xbps-install; then
		xbps-install -Sy 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
		printf >&2 "FAILED TO INSTALL BASE DEPENDENCIES\n"
		# Exit as command not found
		exit 127
	fi

fi

# We'll also bind mount in READ-ONLY useful directories from the host
HOST_MOUNTS_RO="/etc/machine-id /var/lib/flatpak /var/lib/systemd/coredump /var/log/journal"
for host_mount_ro in ${HOST_MOUNTS_RO}; do
	mount_bind /run/host"${host_mount_ro}" "${host_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 /run/media /mnt /run/systemd/journal /run/libvirt /var/mnt /var/lib/libvirt"
for host_mount in ${HOST_MOUNTS}; do
	if ! mount_bind /run/host"${host_mount}" "${host_mount}" rw; then
		printf >&2 "Warning: Cannot bind mound %s to /run/host%s\n" "${host_mount}" "${host_mount}"
	fi
done

# Do not check fqdn when doing sudo, it will not work anyways
if ! grep -q 'Defaults !fqdn' /etc/sudoers; then
	printf "Defaults !fqdn\n" >>/etc/sudoers
fi
# Ensure passwordless sudo is set up for user
if ! grep -q "${container_user_name} ALL = (root) NOPASSWD:ALL" /etc/sudoers; then
	printf "%s ALL = (root) NOPASSWD:ALL\n" "${container_user_name}" >>/etc/sudoers
fi

# If not existing, ensure we have a group for our user.
if ! grep -q "${container_user_name}" /etc/group; then
	groupadd --force --gid "${container_user_uid}" "${container_user_name}"
fi
# Let's add our user to the container
# if the user already exists, just add it to the sudoers groups
if ! useradd \
	--home-dir "${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

# Themes and icons integration works using a bind mount inside the container
# of the host's themes and icons directory. This ensures that the host's home will
# not be littered with files and directories and broken symlinks.
#
# bind mount distrobox directory for themes and icons
mkdir -p "${container_user_home}/.local/share/themes"
mkdir -p "${container_user_home}/.local/share/icons"
# Fix permissions for homw folders
chown "${container_user_uid}":"${container_user_gid}" "${container_user_home}/.local/share/themes"
chown "${container_user_uid}":"${container_user_gid}" "${container_user_home}/.local/share/icons"
if ! mount_bind "/run/host/usr/share/themes" "${container_user_home}/.local/share/themes" rw; then
	printf >&2 "Warning: Cannot bind mound /run/host/usr/share/themes to %s/.local/share/themes\n" "${container_user_home}"
	printf >&2 "Warning: Themes integration with the host is disabled.\n"
fi
if ! mount_bind "/run/host/usr/share/icons" "${container_user_home}/.local/share/icons" rw; then
	printf >&2 "Warning: Cannot bind mound /run/host/usr/share/icons to %s/.local/share/icons\n" "${container_user_home}"
	printf >&2 "Warning: Icons integration with the host is disabled.\n"
fi

printf "container_setup_done\n"
# Keepalive loop
sleep infinity