sysuser-tools/sysusers2shadow.sh

#!/bin/sh
set -eu

# Print the command and run it
run() {
	echo "$@"
	"$@"
}

# Absolute path to busybox, if found
busybox=
for i in /bin/busybox /usr/bin/busybox; do [ -x "$i" ] && busybox=$i; done

while read arg0 arg1 arg2 arg3 arg4
do
	case "$arg0" in
	g)
		ARGUMENTS="${arg1}"
		if [ -n "${arg2}" -a "${arg2}" != "-" ]; then
			ARGUMENTS="-g ${arg2} $ARGUMENTS"
		fi

		if ! /usr/bin/getent group "${arg1}" >> /dev/null; then
			if [ -x "/usr/sbin/groupadd" ]; then
				run /usr/sbin/groupadd -r $ARGUMENTS
			elif [ -x "$busybox" ]; then
				run $busybox addgroup -S $ARGUMENTS
			else
				echo "ERROR: neither groupadd nor busybox found!"
				exit 1
			fi
		fi
		;;
	u)
		ARGUMENTS="${arg1}"
		if [ -n "${arg2}" ] && [ "${arg2}" != "-" ]; then
			ARGUMENTS="-u ${arg2} $ARGUMENTS"
		fi
		if [ -n "${arg4}" ] && [ "${arg4}" != "-" ]; then
			ARGUMENTS="-d ${arg4} $ARGUMENTS"
		else
			ARGUMENTS="-d / $ARGUMENTS"
		fi

		if [ -x /usr/sbin/useradd ]; then
			if ! /usr/bin/getent passwd "${arg1}" >> /dev/null; then
				# this is useradd/shadow specific
				ARGUMENTS="-g ${arg1} $ARGUMENTS"
				/usr/bin/getent group "${arg1}" >> /dev/null || ARGUMENTS="-U $ARGUMENTS"
			
				run /usr/sbin/useradd -r -s /sbin/nologin -c "${arg3}" $ARGUMENTS
			fi
		elif [ -x "$busybox" ]; then
			/usr/bin/getent group "${arg1}" >> /dev/null || $busybox addgroup "${arg1}"

			if ! /usr/bin/getent passwd ${arg1} >> /dev/null; then
				ARGUMENTS="$(echo -G ${arg1} $ARGUMENTS | sed -e 's|-d|-h|g' -e 's|-g|-G|g')"
				run $busybox adduser -S -H -s /sbin/nologin -g "${arg3}" $ARGUMENTS
			fi
		else
			echo "ERROR: neither useradd nor busybox found!"
			exit 1
		fi
	    ;;
	m)
		if [ -x /usr/sbin/usermod ] ; then
				run /usr/sbin/usermod -a -G ${arg2} ${arg1}
		elif [ -x "$busybox" ]; then
				run $busybox addgroup ${arg1} ${arg2}
		else
				echo "ERROR: neither usermod nor busybox found!"
				exit 1
		fi
	    ;;
	r)
		echo "range option ignored: \"$arg0 $arg1 $arg2 $arg3\""
		;;
	*)
	    echo "Syntax Error: \"$arg0\""
	    exit 1
	    ;;
	esac
done