#!/bin/sh
# turnup
# See the help block at the end for documentation.
#
. /etc/default/functions

#
# configuration
#  The following variables control which directories in /var end
#  up on the rootfs and which end up in a temporary file system.
INRAM_MEMSTICK="/var/cache /var/lock /var/log /var/run /var/tmp /var/lib/ipkg"
INRAM_NFS="/var/cache /var/lock /var/run /var/tmp"
INRAM_DISK=""

#
# force: override certain checks
force=

#
# pfile: the uuid/partition file
pfile=/etc/uuid_by_partition

#
# fstype new
#  The type of the file system mounted on "new"  Outputs the last
#  piece of information found, which should be the one for the
#  currently visible mount!
fstype() {
	local cwd dev mp type options pass freq result
	cwd="$(cd "$1"; /bin/pwd)"
	result=
	while read dev mp type options pass freq
	do
		case "$mp" in
		"$cwd")	result="$type";;
		esac
	done </proc/mounts
	echo "$result"
}

#
# fsoptions arguments
#  Collapses the mount (-o) options into a single list which is
#  printed on stdout.  Accepts an arbitrary list of options and
#  just joins them together.
fsoptions() {
	local options
	options=
	while test $# -gt 1
	do
		case "$1" in
		-t)	shift;;
		-o)	if test -n "$2"
			then
				if test -n "$options"
				then
					options="$options,$2"
				else
					options="$2"
				fi
			fi
			shift;;
		esac
		shift
	done
	if test -n "$options"
	then
		echo "$options"
	else
		echo defaults
	fi
}

#
# get_flash <directory> {mount options}
#  mount the flash device, writeable, on the given directory
get_flash() {
	local ffsdir ffsdev

	ffsdir="$1"
	shift
	test -n "$ffsdir" -a -d "$ffsdir" || {
		echo "$0: $ffsdir: internal error, flash mount point not a directory" >&2
		return 1
	}

	ffsdev="$(mtblockdev Flashdisk)"
	umountflash "$ffsdev" &&
	mountflash "$ffsdev" "$ffsdir" "$@"
}

#
# check_rootfs [-i] <root fs directory>
#  Make sure the candidate rootfs is empty
#  Environment: rootdev=device or NFS root path
check_rootfs() {
	local fcount

	case "$1" in
	-i)	shift
		case "$force" in
		-f) return 0;;
		esac

		fcount="$(find "$1" ! -type d -print | wc -l)"
		test "$fcount" -eq 0 && return 0

		echo "turnup: $rootdev: partition contains existing files, specify -f to overwrite" >&2
		return 1;;
	*)	checkmount "$1" && return 0

		echo "turnup: $rootdev: partition does not seem to be a valid root partition" >&2
		echo "  The partition must contain a full operating system.  To ensure that" >&2
		echo "  this is the case it is checked for the following, all of which must" >&2
		echo "  exist for the bootstrap to work:" >&2
		echo
		echo "  1) A directory /mnt." >&2
		echo "  2) A command line interpreter program in /bin/sh." >&2
		echo "  3) The program chroot in /sbin or /usr/sbin." >&2
		echo "  4) The program init in /sbin, /etc or /bin." >&2
		echo
		echo "  One or more of these items is missing.  Mount $rootdev on /mnt" >&2
		echo "  and examine its contents.  You can use turnup disk|nfs -i -f" >&2
		echo "  to copy this operating system onto the disk, but it may overwrite" >&2
		echo "  files on the disk." >&2
		return 1;;
	esac
}

#
# copy_rootfs old new
#  Make a copy of the given root file system, copying only the
#  directories needed.  The root must be the flash file system
copy_rootfs() {
	local old new
	old="$1"
	new="$2"
	test -d "$old" -a -d "$new" || {
		echo "turnup: rootfs: copy $old $new: not a directory" >&2
		return 1
	}
	#
	# There are no problem file names in the flash file system, so
	# it is possible to use -print, not -print0.  The following
	# files and directories are not copied:
	#
	#   /dev/*
	#   /boot, /boot/*
	#   /linuxrc*
	#   /var/*
	echo "turnup: copying root file system" >&2
	(	cd "$1"
		find . -mount -print |
		sed '\@^./dev/@d;\@^./boot/@d;\@^./boot$@d;\@^./linuxrc@d;\@^./var/@d' |
		cpio -p -d -m -u "$2"
	) || {
		echo "turnup: rootfs: cpio $old $new failed" >&2
		return 1
	}
	echo "done" >&2
}

#
# setup_dev new device_table
#  In flash file systems /dev is in ramfs, in disk systems /dev
#  can be populated permanently.  This is done by creating a
#  single entry '.noram' in /dev - the devices init script will
#  then populate the directory without overmounting it.  The
#  devices in the passed in device table are also created, but
#  note that this is insufficient, /etc/init.d/devices must
#  also run.
setup_dev() {
	test -n "$1" -a -d "$1"/dev -a -r "$2" || {
		echo "turnup: setup_dev($1,$2): expected a directory and a file" >&2
		return 1
	}
	echo "turnup: initialising dev file system" >&2
	# init tries to open the following devices:
	#	/dev/console
	#	/dev/tty0
	#	/dev/null
	# syslog, and maybe other things, only work if fd 1 is valid, therefore
	# we must create these devices here...
	makedevs --root="$1" --devtable="$2"
	:>"$1"/dev/.noram
	return 0
}

#
# setup_bootdev new device_table
#  As above but actually uses the supplied device table - this is possible if
#  the table is just used for boot because the extra setup is not required.
setup_bootdev() {
	test -n "$1" -a -d "$1"/dev -a -r "$2" || {
		echo "turnup: setup_bootdev($1,$2): expected a directory and a file" >&2
		return 1
	}
	# NOTE: this fails silently with 0 return code(!) when a directory
	# does not exist yet things are created within it.
	makedevs -r "$1" -D "$2"
}

#
# setup_var new type
#  Populates /var.
#  Removes the /var tmpfs entry from /etc/fstab.
#  Creates links from /var into /media/ram for NFS and Memstick.
setup_var() {
	local ram_targets directory

	test -n "$1" -a -d "$1"/var || {
		echo "turnup: setup_var($1,$2): expected a directory" >&2
		return 1
	}
	case "$2" in
	disk|nfs|memstick);;
	*)	echo "turnup: setup_var($1,$2): expected 'disk', 'nfs' or 'memstick'" >&2
		return 1;;
	esac
	#
	# populate /var, there is a shell script to do this, but it uses
	# absolute path names
	chroot "$1" /bin/busybox sh /etc/init.d/populate-volatile.sh || {
		echo "turnup: /var: could not populate directory" >&2
		return 1
	}

	case "$2" in
	disk)	ram_targets="$INRAM_DISK";;
	nfs)	ram_targets="$INRAM_NFS";;
	memstick)
		ram_targets="$INRAM_MEMSTICK";;
	esac

	for directory in $ram_targets
	do
		rm -rf "$1/$directory"
		ln -s "/media/ram/$directory" "$1/$directory"
	done
	# the startup link is left for the moment, this seems safer
	#rm "$1"/etc/rc?.d/[KS]??populate-var.sh
	# remove the /var tmpfs entry from the new /etc/fstab
	sed -i '\@[ 	]/var[ 	][ 	]*tmpfs[ 	]@d' "$1"/etc/fstab
	echo "turnup: tmpfs will no longer be mounted on /var" >&2
	#
	# Previous versions of turnup removed populate-var.sh from the
	# startup links, this one doesn't, so /var can be made back into
	# a tmpfs just by a change to /etc/fstab.
	return 0
}

#
# setup_syslog new
#  Moves the syslog to a file - appropriate for disk and nfs types, not
#  otherwise.
setup_syslog() {
	test -n "$1" -a -d "$1"/etc || {
		echo "turnup: setup_syslog($1): expected a directory" >&2
		return 1
	}
	#
	# if the syslog is to the buffer redirect it to a file
	if egrep -q '^DESTINATION="buffer"' "$1"/etc/syslog.conf
	then
		if cp "$1"/etc/syslog.conf "$1"/etc/syslog.conf.sav
		then
			# the busybox syslog will fail with ROTATESIZE and ROTATEGENS
			sed -i 's!DESTINATION="buffer"!DESTINATION="file"!
				/^ROTATESIZE=/d
				/^ROTATEGENS=/d' "$1"/etc/syslog.conf
			echo "turnup: /etc/syslog.conf: changed to file buffering" >&2
			echo " Old (buffer) version in /etc/syslog.conf.sav" >&2
			echo " Log messages will be in /var/log/messages" >&2
		else
			echo "turnup: /etc/syslog.conf: failed to make a copy" >&2
			echo " syslog will log to a buffer" >&2
		fi
	fi
	return 0
}

#
# setup_rootfs type new device_table
#  Populates the /dev and /var directories, alters the startup to
#  not mount or populate them further.  Does the right thing according
#  to the given $type
setup_rootfs() {
	local type new table
	type="$1"
	new="$2"
	table="$3"

	test -n "$new" -a -d "$new" -a -f "$table" || {
		echo "turnup: setup_rootfs($type,$new,$table): expected a directory and a file" >&2
		return 1
	}

	case "$type" in
	flash)	return 0;;
	disk)	setup_dev "$new" "$table" &&
		setup_var "$new" "$type" &&
		setup_syslog "$new";;
	memstick)
		setup_bootdev "$new" "$table" &&
		setup_var "$new" "$type" ;;
	nfs)	setup_dev "$new" "$table" &&
		setup_var "$new" "$type" &&
		setup_syslog "$new";;
	*)	echo "turnup: setup_rootfs: $type: unknown rootfs type" >&2
		return 1;;
	esac
	# return code of last setup function
}

#
# setup_fstab new fsdev fstype fsoptions
#  Alters the /etc/fstab entry for / to refer to the correct device and
#  have the correct type and options.  Essential for checkroot to remount
#  / with the correct options.  Writes the initial uuid file.
#  bad, since sed won't fail even if it changes nothing.
setup_fstab() {
	sed -i '\@^[^ 	]*[ 	][ 	]*/[ 	]@s@^.*$@'"$2	/	$3	$4	1  1"'@' "$1"/etc/fstab
	egrep -q "^$2	/	$3	$4	1  1\$" "$1"/etc/fstab || {
		echo "turnup: /etc/fstab: root(/) entry not changed" >&2
		echo "  you probably need to check the options in /etc/fstab" >&2
		echo "  to ensure that the root partition is mounted correctly" >&2
		return 1
	}
	#
	# build $pfile
	uuid_by_partition >"$1""$pfile" ||
		echo "turnup: $pfile: blkid failed (ignored)" >&2
	return 0
}

#
# boot_rootfs <boot type> <flash file system> <sleep time> (<device> <uuid>|<nfsroot>) [options]
#  Change the flash partition (not the current root!) to boot off
#  the new root file system
boot_rootfs() {
	local type ffs sleep device uuid opt

	type="$1"
	ffs="$2"
	sleep="$3"
	device="$4"
	uuid=

	# test this first as the test does not depend on the correctness
	# of the other arguments
	test -n "$ffs" -a -d "$ffs" || {
		echo "turnup: boot_rootfs($type, $ffs, $device): expected directory" >&2
		return 1
	}
	test -x "$ffs"/boot/"$type" || {
		echo "turnup: boot_rootfs($type, $ffs, $device): invalid boot type $type" >&2
		return 1
	}
	shift
	shift

	case "$type" in
	disk)	test -n "$device" -a -b "$device" || {
			echo "turnup: boot_rootfs($ffs, $type, $device): expected block device" >&2
			return 1
		}
		uuid="$3"
		shift 3;;
	nfs)	shift 2;;
	flash)	;;
	ram)	;;
	*)	echo "turnup: boot_rootfs($type, $ffs, $device): unknown type" >&2
		return 1;;
	esac

	#
	# The /linuxrc records the correct options to mount the device,
	# since we have already mounted if correctly with these options
	# we can be sure (maybe) that the boot will work.  If not /boot/disk
	# falls back to flash.
	#
	# This modifies the boot process, until this point no harm has been
	# done to the system, but at this point the boot rootfs will change
	rm -f "$ffs"/linuxrc.new || {
		echo "turnup: boot_rootfs: failed to remove $ffs/linuxrc.new" >&2
		return 1
	}
	case "$type" in
	flash)	ln -s "boot/flash" "$ffs"/linuxrc.new || {
			echo "turnup: boot_rootfs: failed to create $ffs/linuxrc.new" >&2
			return 1
		};;
	ram)	{	echo '#!/bin/sh'
			echo 'leds beep'
			echo 'rm -f /linuxrc.new'
			echo 'ln -s boot/flash /linuxrc.new'
			echo 'mv /linuxrc.new /linuxrc'
			echo 'exec /boot/ram /dev/ram0'
			echo 'exec /boot/flash'
		} >"$ffs"/linuxrc.new &&
		chmod 744 "$ffs"/linuxrc.new || {
			echo "turnup: boot_rootfs: failed to write $ffs/linuxrc.new" >&2
			return 1
		};;
	*)	{	echo '#!/bin/sh'
			echo 'leds beep'
			test "$sleep" -gt 0 && echo -n "sleep='$sleep' "
			test -n "$uuid" && echo -n "UUID='$uuid' "
			echo -n "exec '/boot/$type' '$device'"
			for opt in "$@"
			do
				echo -n " '$opt'"
			done
			echo
			echo 'exec /boot/flash'
		} >"$ffs"/linuxrc.new &&
		chmod 744 "$ffs"/linuxrc.new || {
			echo "turnup: boot_rootfs: failed to write $ffs/linuxrc.new" >&2
			return 1
		};;
	esac
	rm -f "$ffs"/linuxrc.sav || {
		echo "turnup: boot_rootfs: failed to remove $ffs/linuxrc.sav" >&2
		return 1
	}
	ln "$ffs"/linuxrc "$ffs"/linuxrc.sav || {
		echo "turnup: boot_rootfs: failed to save /linuxrc.sav" >&2
		return 1
	}
	mv -f "$ffs"/linuxrc.new "$ffs"/linuxrc || {
		echo "turnup: boot_rootfs: failed to install new /linuxrc" >&2
		return 1
	}
	return 0
}

#
# disk [-m] [-i] [-s<time>] <device> {options}
#  Carefully copy the flash file system to the named device.
disk() {
	local setup_type sleep init device uuid new ffs fst fso

	setup_type=disk
	sleep=0
	init=
	while test $# -gt 0
	do
		case "$1" in
		-f)	force="$1"
			shift;;
		-m)	setup_type=memstick
			shift;;
		-i)	init="$1"
			shift;;
		-s*)	sleep="${1#-s}"
			sleep="${sleep:-10}"
			shift;;
		*)	break;;
		esac
	done

	device="$1"
	test -n "$device" -a -b "$device" || {
		echo "turnup disk: $device: block device required" >&2
		return 1
	}
	shift

	# find the uuid if available
	uuid="$(blkid -c /dev/null -s UUID -o value "$device")"

	# make temporary directories for the mount points
	new="/tmp/rootfs.$$"
	ffs="/tmp/flashdisk.$$"
	mkdir "$new" "$ffs" || {
		echo "turnup: disk: failed to create temporary directories" >&2
		return 1
	}

	# make sure we can get to the flash file system first
	get_flash "$ffs" || {
		rmdir "$new" "$ffs"
		return 1
	}

	# Now mount the device with the given options, note that specifying
	# read only is *not* an option, this is important because the boot/disk
	# script needs a rw file system
	status=1
	fst=
	fso="$(fsoptions "$@")"
	if	if test -n "$uuid"
		then
			mount "$@" -U "$uuid" "$new"
		else
			mount "$@" "$device" "$new"
		fi
	then
		fst="$(fstype "$new")"
		umount "$new" ||
			echo "turnup disk: $device($new): umount does not seem to work" >&2
	fi

	if test -n "$fst" &&
		if test -n "$uuid"
		then
			mount -t "$fst" -o "$fso" -U "$uuid" "$new"
		else
			mount -t "$fst" -o "$fso" "$device" "$new"
		fi
	then
		if rootdev="$device" check_rootfs $init "$new" && {
			test -z "$init" || {
				copy_rootfs "$ffs" "$new" &&
				setup_rootfs "$setup_type" "$new" "$ffs"/etc/device_table
			}
		   }
		then
			setup_fstab "$new" "$device" "$fst" "$fso"
			status=0
		fi

		# clean up the disk.  It is worrying if this umount fails!
		umount "$new" || test "$force" = "-f" || {
			echo "turnup disk: $device: umount failed" >&2
			echo "  you must unmount this device cleanly yourself, then use" >&2
			if test -z "$init"
			then
				echo "  turnup with the -f option to boot from the device" >&2
			else
				echo "  turnup without the -i option to boot from the device" >&2
			fi
			status=1
		}

		# if everything went ok boot from this disk
		if test $status -eq 0
		then
			# memsticks boot like disks, so ignore the -m
			boot_rootfs disk "$ffs" "$sleep" "$device" "$uuid" -t "$fst" -o "$fso"
		fi
	else
		echo "turnup disk: $device($*): unable to mount device on $new" >&2
		# If it worked first time
		if test -n "$fst"
		then
			echo "  options used: -t $fst -o $fso [error in this script]" >&2
			test -n "$uuid" &&
				echo "  uuid: $uuid (passed with -U)" >&2
		fi
	fi

	# clean up the flash file system
	umount "$ffs"
	rmdir "$new" "$ffs"
	return $status
}

#
# boot_reset <type>
#  Resets the boot type to flash or ram, as appropriate
boot_reset() {
	local ffs typ status

	case "$1" in
	flash|ram)type="$1"
		shift;;
	*)	echo "turnup: boot_reset($1): invalid type" >&2
		return 1;;
	esac

	ffs="/tmp/flashdisk.$$"
	mkdir "$ffs" || {
		echo "turnup: $1: failed to create temporary directory" >&2
		return 1
	}

	get_flash "$ffs" || {
		rmdir "$ffs"
		return 1
	}

	# now try to set the /linuxrc appropriately
	boot_rootfs "$type" "$ffs"
	status=$?

	# clean up
	umount "$ffs"
	rmdir "$ffs"
	return $status
}

#
# nfs [-i] <root partition> {options}
#  Copy the flash file system to the given NFS root partition.
nfs() {
	local init nfsroot new ffs

	init=
	while test $# -gt 0
	do
		case "$1" in
		-i)	init="$1"
			shift;;
		-f)	force="$1"
			shift;;
		*)	break;;
		esac
	done

	nfsroot="$1"
	test -n "$nfsroot" || {
		echo "turnup nfs: $nfsroot: NFS root file system required" >&2
		return 1
	}
	shift

	# make temporary directories for the mount points
	new="/tmp/rootfs.$$"
	ffs="/tmp/flashdisk.$$"
	mkdir "$new" "$ffs" || {
		echo "turnup nfs: failed to create temporary directories" >&2
		return 1
	}

	# make sure we can get to the flash file system first
	get_flash "$ffs" || {
		rmdir "$new" "$ffs"
		return 1
	}

	# Now mount the device with the given options, note that specifying
	# read only is *not* an option, this is important because the boot/disk
	# script needs a rw file system
	status=1
	fst=
	# These settings for for NFS, something better will probably have to
	# be done to support other network file systems.
	nfsopt="nolock,noatime,hard,intr,rsize=1024,wsize=1024"
	fso="$(fsoptions -o "$nfsopt" "$@")"
	if mount -o "$nfsopt" "$@" "$nfsroot" "$new"
	then
		fst="$(fstype "$new")"
		umount "$new" ||
			echo "turnup nfs: $nfsroot($new): umount does not seem to work" >&2
	fi

	if test -n "$fst" && mount -t "$fst" -o "$fso" "$nfsroot" "$new"
	then
		if :>"$new"/ttt && test -O "$new"/ttt && rm "$new"/ttt
		then
			if rootdev="$nfsroot" check_rootfs $init "$new" && {
				test -z "$init" || {
					copy_rootfs "$ffs" "$new" &&
					setup_rootfs nfs "$new" "$ffs"/etc/device_table
				}
			   }
			then
				setup_fstab "$new" "$nfsroot" "$fst" "$fso"
				status=0
			fi
		else
			echo "turnup nfs: $nfsroot: partition must be exported no_root_squash" >&2
		fi

		# clean up the disk.  It is worrying if this umount fails!
		umount "$new" || test "$force" = "-f" || {
			echo "turnup nfs: $nfsroot: umount failed" >&2
			if test $status -eq 0
			then
				echo "  you must unmount this partition cleanly yourself, then use" >&2
				if test -z "$init"
				then
					echo "  turnup with the -f option to boot from the NFS root" >&2
				else
					echo "  turnup without the -i option to boot from the NFS root" >&2
				fi
				status=1
			fi
		}

		# if everything went ok boot from this disk
		if test $status -eq 0
		then
			# the options used are exactly those which worked before.
			boot_rootfs nfs "$ffs" 0 "$nfsroot" -t nfs -o "$fso"
		fi
	else
		echo "turnup nfs: $nfsroot($*): unable to mount device on $new" >&2
		# If it worked first time
		if test -n "$fst"
		then
			echo "  options obtained: -t $fst -o $fso" >&2
		fi
	fi

	# clean up the flash file system
	umount "$ffs"
	rmdir "$new" "$ffs"
	return $status
}

#
# read_one 'prompt' 'group' 'name'
#  read a single value
read_one() {
	local n o
	o="$(sysval "$2" "$3")"
	echo -n "$1 [$o]: " >/dev/tty
	read n </dev/tty
	test -z "$n" && n="$o"
	eval "$3='$n'"
}

#
# init_network
#  Change the network initialisation
init_network() {
	# fix the root password
	echo "Please enter a new password for 'root'." >/dev/tty
	echo "The password must be non-empty for ssh login to succeed!" >/dev/tty
	passwd
	# now the network configuration
	read_one "Host name" network disk_server_name
	read_one "Domain name" network w_d_name
	read_one "Boot protocol (dhcp|static)" network bootproto
	case "$bootproto" in
	static) read_one "IP address" network ip_addr
		read_one "IP netmask" network netmask
		read_one "IP gateway" network gateway
		read_one "First DNS server" network dns_server1
		read_one "Second DNS server" network dns_server2
		read_one "Third DNS server" network dns_server3
		echo "$ip_addr       $disk_server_name" >> /etc/hosts
		;;
	dhcp)	sed -i -e "s/localhost\$/localhost $disk_server_name/" /etc/hosts
		;;
	*)	bootproto=dhcp;;
	esac
	#
	# The other stuff which cannot be changed
	hw_addr="$(config mac)"
	lan_interface="$(config iface)"
	#
	# Write this out to a new sysconf
	{	echo "[network]"
		echo "hw_addr=$hw_addr"
		echo "lan_interface=$lan_interface"
		test -n "$disk_server_name" && echo "disk_server_name=$disk_server_name"
		test -n "$w_d_name" && echo "w_d_name=$w_d_name"
		echo "bootproto=$bootproto"
		case "$bootproto" in
		static)	echo "ip_addr=$ip_addr"
			test -n "$netmask" && echo "netmask=$netmask"
			test -n "$gateway" && echo "gateway=$gateway"
			test -n "$dns_server1" && echo "dns_server1=$dns_server1"
			test -n "$dns_server2" && echo "dns_server2=$dns_server2"
			test -n "$dns_server3" && echo "dns_server3=$dns_server3"
			;;
		esac
	} >/etc/default/sysconf
	#
	# And reload the result
	sysconf reload
	#
	# The remove the spurious 'init' motd
	rm /etc/motd
}

#
# Basic command switch (this should be the only thing in this
# script which actually does anything!)
case "$1" in
init)	shift
	if init_network "$@"
	then
		echo "turnup init: you must reboot for the changes to take effect" >&2
		echo " You may want to run 'turnup preserve' to save these settings," >&2
		echo " after making any additional configuration changes which you" >&2
		echo " require." >&2
	else
		exit 1
	fi;;
disk)	shift
	disk "$@";;
memstick)
	shift
	disk -m "$@" -o noatime;;
nfs)	shift
	nfs "$@";;
flash)	boot_reset flash;;
ram)	boot_reset ram;;
preserve)
	shift
	sysconf save "$@";;
restore)
	shift
	sysconf restore "$@";;
*)	echo "\
usage: turnup command [options]
 commands:
  help
    output this help
  init
    correct errors in network information
    initialise network information when DHCP is not available
    change network information
  disk [-i] [-s<seconds>] <device>|<uuid> [mount options]
    With -i make <device> a bootable file system then (with or
    without -i) arrange for the next reboot to use that device.
    The device must already be formatted as a file system, with
    -i it must be completely empty, without it must contain an
    apparently bootable file system. -s (for example -s5)
    specifies a delay in seconds to wait at boot time before
    mounting the device.
  memstick [-i] <device>|<uuid> [mount options]
    Behaves as disk however options appropriate to a flash memory
    stick are automatically added
  nfs [-i] <nfs mount path> [mount options]
    <nfs mount path> must be a mountable NFS file system.  With
    -i the partition must be empty and is initialised with a
    bootable file system.  Without -i the partition must already
    contain a bootable file system.  In either case the NFS
    partition must be available to be mounted without root id
    sqashing (i.e. root must be root) and it will be selected
    as the root file system for subsequent reboots.
    A default set of -o options are provided, additional options
    may be given on the command line (multiple -o options will
    be combined into a single -o).
  flash
    Revert to booting from the flash disk on next reboot.
  ram
    Boot (once) into a ramdisk, subsequent boots will be to
    the flash file system.
  preserve
    Save the system configuration to the SysConf partition, you
    will need to create the SysConf partition from the boot loader
    before using this if SysConf does not already exist.  This
    just runs 'sysconf save'.
  restore
    Restore a previously saved system configuration.  This just
    runs 'sysconf restore'.
 disk formatting:
  The argument to 'nfs' or 'disk' must be an empty partition
  of sufficient size to hold the root file system (at least
  16MByte but more is recommended to allow package installation).
  An appropriate ext3 partition can be made using the command:

    mke2fs -j <device>  # for example: /dev/sda1

  An appropriate NFS partition can be emptied using 'rm', but
  must be set up (exported) on the NFS server." >&2
	exit 0;;
esac
# Exit with return code from command.