sysuser-tools/sysusers2shadow.sh

#!/bin/sh
set -eu

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

if [ -x /usr/bin/systemd-sysusers ]; then

    # Use systemd-sysusers and let it read the input directly from stdin
    /usr/bin/systemd-sysusers -
    # We need to clear the nscd cache, as systemd-sysusers could have
    # triggered a negative cache entry
    if [ -x /usr/sbin/nscd ]; then
	/usr/sbin/nscd -i passwd ||:
	/usr/sbin/nscd -i group ||:
    fi
else

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

    while read LINE
    do
	# "eval set" to do proper splitting while respecting quotes
	eval set -- $LINE
	case "${1-}" in
	    \#*|"")
	    ;;
	    g)
		shift
		ARGUMENTS="$1"
		if [ -n "${2-}" ] && [ "$2" != "-" ]; then
		    ARGUMENTS="-g $2 $ARGUMENTS"
		fi

		if ! /usr/bin/getent group "$1" >> /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)
		shift
		ARGUMENTS="$1"
		if [ -n "${2-}" ] && [ "$2" != "-" ]; then
		    ARGUMENTS="-u $2 $ARGUMENTS"
		fi
		homedir="/" # If null, empty or '-'
		if [ "${4:--}" != "-" ]; then
		    homedir="$4"
		fi

		if [ -x /usr/sbin/useradd ]; then
		    if ! /usr/bin/getent passwd "$1" >> /dev/null; then
			# this is useradd/shadow specific
			if /usr/bin/getent group "$1" >> /dev/null; then
			    ARGUMENTS="-g $1 $ARGUMENTS"
			else
			    ARGUMENTS="-U $ARGUMENTS"
			fi

			run /usr/sbin/useradd -r -s /sbin/nologin -c "$3" -d "${homedir}" $ARGUMENTS
		    fi
		elif [ -x "$busybox" ]; then
		    /usr/bin/getent group "$1" >> /dev/null || $busybox addgroup -S "$1"

		    if ! /usr/bin/getent passwd "$1" >> /dev/null; then
			run $busybox adduser -S -H -s /sbin/nologin -g "$3" -G "$1" -h "${homedir}" $ARGUMENTS
		    fi
		else
		    echo "ERROR: neither useradd nor busybox found!"
		    exit 1
		fi
		;;
	    m)
		shift
		if [ -x /usr/sbin/usermod ] ; then
		    run /usr/sbin/usermod -a -G $2 $1
		elif [ -x "$busybox" ]; then
		    run $busybox addgroup $1 $2
		else
		    echo "ERROR: neither usermod nor busybox found!"
		    exit 1
		fi
		;;
	    r)
		echo "range option ignored: \"$LINE\""
		;;
	    *)
		echo "Syntax Error: \"$LINE\""
		exit 1
		;;
	esac
    done
fi