xref: /src/etc/rc.subr

# $NetBSD: rc.subr,v 1.75 2009/04/28 03:03:52 reed Exp $
#
# Copyright (c) 1997-2004 The NetBSD Foundation, Inc.
# All rights reserved.
#
# This code is derived from software contributed to The NetBSD Foundation
# by Luke Mewburn.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
# ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
# TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
# PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
# BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
#
# rc.subr
#	functions used by various rc scripts
#

: ${rcvar_manpage:='rc.conf(5)'}
: ${RC_PID:=$$} ; export RC_PID

#
#	functions
#	---------

#
# checkyesno var
#	Test $1 variable, and warn if not set to YES or NO.
#	Return 0 if it's "yes" (et al), nonzero otherwise.
#
checkyesno()
{
	eval _value=\$${1}
	case $_value in

		#	"yes", "true", "on", or "1"
	[Yy][Ee][Ss]|[Tt][Rr][Uu][Ee]|[Oo][Nn]|1)
		return 0
		;;

		#	"no", "false", "off", or "0"
	[Nn][Oo]|[Ff][Aa][Ll][Ss][Ee]|[Oo][Ff][Ff]|0)
		return 1
		;;
	*)
		warn "\$${1} is not set properly - see ${rcvar_manpage}."
		return 1
		;;
	esac
}

#
# reverse_list list
#	print the list in reverse order
#
reverse_list()
{
	_revlist=
	for _revfile; do
		_revlist="$_revfile $_revlist"
	done
	echo $_revlist
}

#
# If booting directly to multiuser, send SIGTERM to
# the parent (/etc/rc) to abort the boot.
# Otherwise just exit.
#
stop_boot()
{
	if [ "$autoboot" = yes ]; then
		echo "ERROR: ABORTING BOOT (sending SIGTERM to parent)!"
		kill -TERM ${RC_PID}
	fi
	exit 1
}

#
# mount_critical_filesystems type
#	Go through the list of critical filesystems as provided in
#	the rc.conf(5) variable $critical_filesystems_${type}, checking
#	each one to see if it is mounted, and if it is not, mounting it.
#
mount_critical_filesystems()
{
	eval _fslist=\$critical_filesystems_${1}
	for _fs in $_fslist; do
		mount | (
			_ismounted=false
			while read what _on on _type type; do
				if [ $on = $_fs ]; then
					_ismounted=true
				fi
			done
			if $_ismounted; then
				:
			else
				mount $_fs >/dev/null 2>&1
			fi
		)
	done
}

#
# check_pidfile pidfile procname [interpreter]
#	Parses the first line of pidfile for a PID, and ensures
#	that the process is running and matches procname.
#	Prints the matching PID upon success, nothing otherwise.
#	interpreter is optional; see _find_processes() for details.
#
check_pidfile()
{
	_pidfile=$1
	_procname=$2
	_interpreter=$3
	if [ -z "$_pidfile" -o -z "$_procname" ]; then
		err 3 'USAGE: check_pidfile pidfile procname [interpreter]'
	fi
	if [ ! -f $_pidfile ]; then
		return
	fi
	read _pid _junk < $_pidfile
	if [ -z "$_pid" ]; then
		return
	fi
	_find_processes $_procname ${_interpreter:-.} '-p '"$_pid"
}

#
# check_process procname [interpreter]
#	Ensures that a process (or processes) named procname is running.
#	Prints a list of matching PIDs.
#	interpreter is optional; see _find_processes() for details.
#
check_process()
{
	_procname=$1
	_interpreter=$2
	if [ -z "$_procname" ]; then
		err 3 'USAGE: check_process procname [interpreter]'
	fi
	_find_processes $_procname ${_interpreter:-.} '-ax'
}

#
# _find_processes procname interpreter psargs
#	Search for procname in the output of ps generated by psargs.
#	Prints the PIDs of any matching processes, space separated.
#
#	If interpreter == ".", check the following variations of procname
#	against the first word of each command:
#		procname
#		`basename procname`
#		`basename procname` + ":"
#		"(" + `basename procname` + ")"
#
#	If interpreter != ".", read the first line of procname, remove the
#	leading #!, normalise whitespace, append procname, and attempt to
#	match that against each command, either as is, or with extra words
#	at the end.  As an alternative, to deal with interpreted daemons
#	using perl, the basename of the interpreter plus a colon is also
#	tried as the prefix to procname.
#
_find_processes()
{
	if [ $# -ne 3 ]; then
		err 3 'USAGE: _find_processes procname interpreter psargs'
	fi
	_procname=$1
	_interpreter=$2
	_psargs=$3

	_pref=
	_procnamebn=${_procname##*/}
	if [ $_interpreter != "." ]; then	# an interpreted script
		read _interp < ${_chroot:-}/$_procname	# read interpreter name
		_interp=${_interp#\#!}		# strip #!
		set -- $_interp
		if [ $_interpreter != $1 ]; then
			warn "\$command_interpreter $_interpreter != $1"
		fi
		_interp="$* $_procname"		# cleanup spaces, add _procname
		_interpbn=${1##*/}
		_fp_args='_argv'
		_fp_match='case "$_argv" in
		    ${_interp}|"${_interp} "*|"${_interpbn}: "*${_procnamebn}*)'
	else					# a normal daemon
		_fp_args='_arg0 _argv'
		_fp_match='case "$_arg0" in
		    $_procname|$_procnamebn|${_procnamebn}:|"(${_procnamebn})")'
	fi

	_proccheck='
		ps -o "pid,command" '"$_psargs"' |
		while read _npid '"$_fp_args"'; do
			case "$_npid" in
			    PID)
				continue ;;
			esac ; '"$_fp_match"'
				echo -n "$_pref$_npid" ;
				_pref=" "
				;;
			esac
		done'

#echo 1>&2 "proccheck is :$_proccheck:"
	eval $_proccheck
}

#
# wait_for_pids pid [pid ...]
#	spins until none of the pids exist
#
wait_for_pids()
{
	_list="$@"
	if [ -z "$_list" ]; then
		return
	fi
	_prefix=
	while true; do
		_nlist="";
		for _j in $_list; do
			if kill -0 $_j 2>/dev/null; then
				_nlist="${_nlist}${_nlist:+ }$_j"
			fi
		done
		if [ -z "$_nlist" ]; then
			break
		fi
		_list=$_nlist
		echo -n ${_prefix:-"Waiting for PIDS: "}$_list
		_prefix=", "
		sleep 2
	done
	if [ -n "$_prefix" ]; then
		echo "."
	fi
}

#
# run_rc_command argument
#	Search for argument in the list of supported commands, which is:
#		"start stop restart rcvar status poll ${extra_commands}"
#	If there's a match, run ${argument}_cmd or the default method
#	(see below).
#
#	If argument has a given prefix, then change the operation as follows:
#		Prefix	Operation
#		------	---------
#		fast	Skip the pid check, and set rc_fast=yes
#		force	Set ${rcvar} to YES, and set rc_force=yes
#		one	Set ${rcvar} to YES
#
#	The following globals are used:
#
#	Name		Needed	Purpose
#	----		------	-------
#	name		y	Name of script.
#
#	command		n	Full path to command.
#				Not needed if ${rc_arg}_cmd is set for
#				each keyword.
#
#	command_args	n	Optional args/shell directives for command.
#
#	command_interpreter n	If not empty, command is interpreted, so
#				call check_{pidfile,process}() appropriately.
#
#	extra_commands	n	List of extra commands supported.
#
#	pidfile		n	If set, use check_pidfile $pidfile $command,
#				otherwise use check_process $command.
#				In either case, only check if $command is set.
#
#	procname	n	Process name to check for instead of $command.
#
#	rcvar		n	This is checked with checkyesno to determine
#				if the action should be run.
#
#	${name}_chroot	n	Directory to chroot to before running ${command}
#				Requires /usr to be mounted.
#
#	${name}_chdir	n	Directory to cd to before running ${command}
#				(if not using ${name}_chroot).
#
#	${name}_flags	n	Arguments to call ${command} with.
#				NOTE:	$flags from the parent environment
#					can be used to override this.
#
#	${name}_env	n	Additional environment variable settings
#				for running ${command}
#
#	${name}_nice	n	Nice level to run ${command} at.
#
#	${name}_user	n	User to run ${command} as, using su(1) if not
#				using ${name}_chroot.
#				Requires /usr to be mounted.
#
#	${name}_group	n	Group to run chrooted ${command} as.
#				Requires /usr to be mounted.
#
#	${name}_groups	n	Comma separated list of supplementary groups
#				to run the chrooted ${command} with.
#				Requires /usr to be mounted.
#
#	${rc_arg}_cmd	n	If set, use this as the method when invoked;
#				Otherwise, use default command (see below)
#
#	${rc_arg}_precmd n	If set, run just before performing the
#				${rc_arg}_cmd method in the default
#				operation (i.e, after checking for required
#				bits and process (non)existence).
#				If this completes with a non-zero exit code,
#				don't run ${rc_arg}_cmd.
#
#	${rc_arg}_postcmd n	If set, run just after performing the
#				${rc_arg}_cmd method, if that method
#				returned a zero exit code.
#
#	required_dirs	n	If set, check for the existence of the given
#				directories before running the default
#				(re)start command.
#
#	required_files	n	If set, check for the readability of the given
#				files before running the default (re)start
#				command.
#
#	required_vars	n	If set, perform checkyesno on each of the
#				listed variables before running the default
#				(re)start command.
#
#	Default behaviour for a given argument, if no override method is
#	provided:
#
#	Argument	Default behaviour
#	--------	-----------------
#	start		if !running && checkyesno ${rcvar}
#				${command}
#
#	stop		if ${pidfile}
#				rc_pid=$(check_pidfile $pidfile $command)
#			else
#				rc_pid=$(check_process $command)
#			kill $sig_stop $rc_pid
#			wait_for_pids $rc_pid
#			($sig_stop defaults to TERM.)
#
#	reload		Similar to stop, except use $sig_reload instead,
#			and doesn't wait_for_pids.
#			$sig_reload defaults to HUP.
#
#	restart		Run `stop' then `start'.
#
#	status		Show if ${command} is running, etc.
#
#	poll		Wait for ${command} to exit.
#
#	rcvar		Display what rc.conf variable is used (if any).
#
#	Variables available to methods, and after run_rc_command() has
#	completed:
#
#	Variable	Purpose
#	--------	-------
#	rc_arg		Argument to command, after fast/force/one processing
#			performed
#
#	rc_flags	Flags to start the default command with.
#			Defaults to ${name}_flags, unless overridden
#			by $flags from the environment.
#			This variable may be changed by the precmd method.
#
#	rc_pid		PID of command (if appropriate)
#
#	rc_fast		Not empty if "fast" was provided (q.v.)
#
#	rc_force	Not empty if "force" was provided (q.v.)
#
#
run_rc_command()
{
	rc_arg=$1
	if [ -z "$name" ]; then
		err 3 'run_rc_command: $name is not set.'
	fi

	_rc_prefix=
	case "$rc_arg" in
	fast*)				# "fast" prefix; don't check pid
		rc_arg=${rc_arg#fast}
		rc_fast=yes
		;;
	force*)				# "force" prefix; always run
		rc_force=yes
		_rc_prefix=force
		rc_arg=${rc_arg#${_rc_prefix}}
		if [ -n "${rcvar}" ]; then
			eval ${rcvar}=YES
		fi
		;;
	one*)				# "one" prefix; set ${rcvar}=yes
		_rc_prefix=one
		rc_arg=${rc_arg#${_rc_prefix}}
		if [ -n "${rcvar}" ]; then
			eval ${rcvar}=YES
		fi
		;;
	esac

	_keywords="start stop restart rcvar"
	if [ -n "$extra_commands" ]; then
		_keywords="${_keywords} ${extra_commands}"
	fi
	rc_pid=
	_pidcmd=
	_procname=${procname:-${command}}

					# setup pid check command if not fast
	if [ -z "$rc_fast" -a -n "$_procname" ]; then
		if [ -n "$pidfile" ]; then
			_pidcmd='rc_pid=$(check_pidfile '"$pidfile $_procname $command_interpreter"')'
		else
			_pidcmd='rc_pid=$(check_process '"$_procname $command_interpreter"')'
		fi
		if [ -n "$_pidcmd" ]; then
			_keywords="${_keywords} status poll"
		fi
	fi

	if [ -z "$rc_arg" ]; then
		rc_usage "$_keywords"
	fi

	if [ -n "$flags" ]; then	# allow override from environment
		rc_flags=$flags
	else
		eval rc_flags=\$${name}_flags
	fi
	eval _chdir=\$${name}_chdir	_chroot=\$${name}_chroot \
	    _nice=\$${name}_nice	_user=\$${name}_user \
	    _group=\$${name}_group	_groups=\$${name}_groups \
	    _env=\"\$${name}_env\"

	if [ -n "$_user" ]; then	# unset $_user if running as that user
		if [ "$_user" = "$(id -un)" ]; then
			unset _user
		fi
	fi

					# if ${rcvar} is set, and $1 is not
					# "rcvar", then run
					#	checkyesno ${rcvar}
					# and return if that failed or warn
					# user and exit when interactive
					#
	if [ -n "${rcvar}" -a "$rc_arg" != "rcvar" ]; then
		if ! checkyesno ${rcvar}; then
					# check whether interactive or not
			if [ -n "$_run_rc_script" ]; then
				return 0
			fi
			for _elem in $_keywords; do
				if [ "$_elem" = "$rc_arg" ]; then
					echo 1>&2 "\$${rcvar} is not enabled - see ${rcvar_manpage}."
					echo 1>&2 "Use the following if you wish to perform the operation:"
					echo 1>&2 "  $0 one${rc_arg}"
					exit 1
				fi
			done
			echo 1>&2 "$0: unknown directive '$rc_arg'."
			rc_usage "$_keywords"
		fi
	fi

	eval $_pidcmd			# determine the pid if necessary

	for _elem in $_keywords; do
		if [ "$_elem" != "$rc_arg" ]; then
			continue
		fi

					# if there's a custom ${XXX_cmd},
					# run that instead of the default
					#
		eval _cmd=\$${rc_arg}_cmd _precmd=\$${rc_arg}_precmd \
		    _postcmd=\$${rc_arg}_postcmd
		if [ -n "$_cmd" ]; then
					# if the precmd failed and force
					# isn't set, exit
					#
			if ! eval $_precmd && [ -z "$rc_force" ]; then
				return 1
			fi

			if ! eval $_cmd && [ -z "$rc_force" ]; then
				return 1
			fi
			eval $_postcmd
			return 0
		fi

		case "$rc_arg" in	# default operations...

		status)
			if [ -n "$rc_pid" ]; then
				echo "${name} is running as pid $rc_pid."
			else
				echo "${name} is not running."
				return 1
			fi
			;;

		start)
			if [ -n "$rc_pid" ]; then
				echo 1>&2 "${name} already running? (pid=$rc_pid)."
				exit 1
			fi

			if [ ! -x ${_chroot}${command} ]; then
				return 0
			fi

					# check for required variables,
					# directories, and files
					#
			for _f in $required_vars; do
				if ! checkyesno $_f; then
					warn "\$${_f} is not enabled."
					if [ -z "$rc_force" ]; then
						return 1
					fi
				fi
			done
			for _f in $required_dirs; do
				if [ ! -d "${_f}/." ]; then
					warn "${_f} is not a directory."
					if [ -z "$rc_force" ]; then
						return 1
					fi
				fi
			done
			for _f in $required_files; do
				if [ ! -r "${_f}" ]; then
					warn "${_f} is not readable."
					if [ -z "$rc_force" ]; then
						return 1
					fi
				fi
			done

					# if the precmd failed and force
					# isn't set, exit
					#
			if ! eval $_precmd && [ -z "$rc_force" ]; then
				return 1
			fi

					# setup the command to run, and run it
					#
			echo "Starting ${name}."
			if [ -n "$_chroot" ]; then
				_doit="\
${_env:+env $_env }\
${_nice:+nice -n $_nice }\
chroot ${_user:+-u $_user }${_group:+-g $_group }${_groups:+-G $_groups }\
$_chroot $command $rc_flags $command_args"
			else
				_doit="\
${_chdir:+cd $_chdir; }\
${_env:+env $_env }\
${_nice:+nice -n $_nice }\
$command $rc_flags $command_args"
				if [ -n "$_user" ]; then
				    _doit="su -m $_user -c 'sh -c \"$_doit\"'"
				fi
			fi

					# if the cmd failed and force
					# isn't set, exit
					#
			if ! eval $_doit && [ -z "$rc_force" ]; then
				return 1
			fi

					# finally, run postcmd
					#
			eval $_postcmd
			;;

		stop)
			if [ -z "$rc_pid" ]; then
				if [ -n "$pidfile" ]; then
					echo 1>&2 \
				    "${name} not running? (check $pidfile)."
				else
					echo 1>&2 "${name} not running?"
				fi
				exit 1
			fi

					# if the precmd failed and force
					# isn't set, exit
					#
			if ! eval $_precmd && [ -z "$rc_force" ]; then
				return 1
			fi

					# send the signal to stop
					#
			echo "Stopping ${name}."
			_doit="kill -${sig_stop:-TERM} $rc_pid"
			if [ -n "$_user" ]; then
				_doit="su -m $_user -c 'sh -c \"$_doit\"'"
			fi

					# if the stop cmd failed and force
					# isn't set, exit
					#
			if ! eval $_doit && [ -z "$rc_force" ]; then
				return 1
			fi

					# wait for the command to exit,
					# and run postcmd.
			wait_for_pids $rc_pid
			eval $_postcmd
			;;

		reload)
			if [ -z "$rc_pid" ]; then
				if [ -n "$pidfile" ]; then
					echo 1>&2 \
				    "${name} not running? (check $pidfile)."
				else
					echo 1>&2 "${name} not running?"
				fi
				exit 1
			fi
			echo "Reloading ${name} config files."
			if ! eval $_precmd && [ -z "$rc_force" ]; then
				return 1
			fi
			_doit="kill -${sig_reload:-HUP} $rc_pid"
			if [ -n "$_user" ]; then
				_doit="su -m $_user -c 'sh -c \"$_doit\"'"
			fi
			if ! eval $_doit && [ -z "$rc_force" ]; then
				return 1
			fi
			eval $_postcmd
			;;

		restart)
			if ! eval $_precmd && [ -z "$rc_force" ]; then
				return 1
			fi
					# prevent restart being called more
					# than once by any given script
					#
			if ${_rc_restart_done:-false}; then
				return 0
			fi
			_rc_restart_done=true

			( $0 ${_rc_prefix}stop )
			$0 ${_rc_prefix}start

			eval $_postcmd
			;;

		poll)
			if [ -n "$rc_pid" ]; then
				wait_for_pids $rc_pid
			fi
			;;

		rcvar)
			echo "# $name"
			if [ -n "$rcvar" ]; then
				if checkyesno ${rcvar}; then
					echo "\$${rcvar}=YES"
				else
					echo "\$${rcvar}=NO"
				fi
			fi
			;;

		*)
			rc_usage "$_keywords"
			;;

		esac
		return 0
	done

	echo 1>&2 "$0: unknown directive '$rc_arg'."
	rc_usage "$_keywords"
	exit 1
}

#
# run_rc_script file arg
#	Start the script `file' with `arg', and correctly handle the
#	return value from the script.  If `file' ends with `.sh', it's
#	sourced into the current environment.  If `file' appears to be
#	a backup or scratch file, ignore it.  Otherwise if it's
#	executable run as a child process.
#
run_rc_script()
{
	_file=$1
	_arg=$2
	if [ -z "$_file" -o -z "$_arg" ]; then
		err 3 'USAGE: run_rc_script file arg'
	fi

	_run_rc_script=true

	unset	name command command_args command_interpreter \
		extra_commands pidfile procname \
		rcvar required_dirs required_files required_vars
	eval unset ${_arg}_cmd ${_arg}_precmd ${_arg}_postcmd

	case "$_file" in
	*.sh)				# run in current shell
		set $_arg ; . $_file
		;;
	*[~#]|*.OLD|*.orig|*,v)		# scratch file; skip
		warn "Ignoring scratch file $_file"
		;;
	*)				# run in subshell
		if [ -x $_file ]; then
			if [ -n "$rc_fast_and_loose" ]; then
				set $_arg ; . $_file
			else
				( set $_arg ; . $_file )
			fi
		fi
		;;
	esac
}

#
# load_rc_config command
#	Source in the configuration file for a given command.
#
load_rc_config()
{
	_command=$1
	if [ -z "$_command" ]; then
		err 3 'USAGE: load_rc_config command'
	fi

	if ${_rc_conf_loaded:-false}; then
		:
	else
		. /etc/rc.conf
		_rc_conf_loaded=true
	fi
	if [ -f /etc/rc.conf.d/"$_command" ]; then
		. /etc/rc.conf.d/"$_command"
	fi
}

#
# load_rc_config_var cmd var
#	Read the rc.conf(5) var for cmd and set in the
#	current shell, using load_rc_config in a subshell to prevent
#	unwanted side effects from other variable assignments.
#
load_rc_config_var()
{
	if [ $# -ne 2 ]; then
		err 3 'USAGE: load_rc_config_var cmd var'
	fi
	eval $(eval '(
		load_rc_config '$1' >/dev/null;
                if [ -n "${'$2'}" -o "${'$2'-UNSET}" != "UNSET" ]; then
			echo '$2'=\'\''${'$2'}\'\'';
		fi
	)' )
}

#
# rc_usage commands
#	Print a usage string for $0, with `commands' being a list of
#	valid commands.
#
rc_usage()
{
	echo -n 1>&2 "Usage: $0 [fast|force|one]("

	_sep=
	for _elem; do
		echo -n 1>&2 "$_sep$_elem"
		_sep="|"
	done
	echo 1>&2 ")"
	exit 1
}

#
# err exitval message
#	Display message to stderr and log to the syslog, and exit with exitval.
#
err()
{
	exitval=$1
	shift

	if [ -x /usr/bin/logger ]; then
		logger "$0: ERROR: $*"
	fi
	echo 1>&2 "$0: ERROR: $*"
	exit $exitval
}

#
# warn message
#	Display message to stderr and log to the syslog.
#
warn()
{
	if [ -x /usr/bin/logger ]; then
		logger "$0: WARNING: $*"
	fi
	echo 1>&2 "$0: WARNING: $*"
}

#
# backup_file action file cur backup
#	Make a backup copy of `file' into `cur', and save the previous
#	version of `cur' as `backup' or use rcs for archiving.
#
#	This routine checks the value of the backup_uses_rcs variable,
#	which can be either YES or NO.
#
#	The `action' keyword can be one of the following:
#
#	add		`file' is now being backed up (and is possibly
#			being reentered into the backups system).  `cur'
#			is created and RCS files, if necessary, are
#			created as well.
#
#	update		`file' has changed and needs to be backed up.
#			If `cur' exists, it is copied to to `back' or
#			checked into RCS (if the repository file is old),
#			and then `file' is copied to `cur'.  Another RCS
#			check in done here if RCS is being used.
#
#	remove		`file' is no longer being tracked by the backups
#			system.  If RCS is not being used, `cur' is moved
#			to `back', otherwise an empty file is checked in,
#			and then `cur' is removed.
#
#
backup_file()
{
	_action=$1
	_file=$2
	_cur=$3
	_back=$4

	if checkyesno backup_uses_rcs; then
		_msg0="backup archive"
		_msg1="update"

		# ensure that history file is not locked
		if [ -f $_cur,v ]; then
			rcs -q -u -U -M $_cur
		fi

		# ensure after switching to rcs that the
		# current backup is not lost
		if [ -f $_cur ]; then
			# no archive, or current newer than archive
			if [ ! -f $_cur,v -o $_cur -nt $_cur,v ]; then
				ci -q -f -u -t-"$_msg0" -m"$_msg1" $_cur
				rcs -q -kb -U $_cur
				co -q -f -u $_cur
			fi
		fi

		case $_action in
		add|update)
			cp -p $_file $_cur
			ci -q -f -u -t-"$_msg0" -m"$_msg1" $_cur
			rcs -q -kb -U $_cur
			co -q -f -u $_cur
			chown root:wheel $_cur $_cur,v
			;;
		remove)
			cp /dev/null $_cur
			ci -q -f -u -t-"$_msg0" -m"$_msg1" $_cur
			rcs -q -kb -U $_cur
			chown root:wheel $_cur $_cur,v
			rm $_cur
			;;
		esac
	else
		case $_action in
		add|update)
			if [ -f $_cur ]; then
				cp -p $_cur $_back
			fi
			cp -p $_file $_cur
			chown root:wheel $_cur
			;;
		remove)
			mv -f $_cur $_back
			;;
		esac
	fi
}

_rc_subr_loaded=: