Problem
—
the breakthrough file system in FreeBSD 7 (ported from Sun's
)
delivers virtually unlimited capacity, provable data integrity,
and near-zero administration. However FreeBSD's
does not yet support installing the system onto anything more exotic
than a commonly used UFS partition scheme. Furthermore FreeBSD's boot
cannot yet load the kernel and modules from ZFS.
Solutions
Install FreeBSD onto a bootable USB flash drive along with a copy of
the script on it.
Boot from the USB flash drive and run the script.
This script can be used to
prepare the bootable USB drive:
#!/bin/sh
#
# HOWTO/script to create a USB mounted bootable "root" install for
# bootstrapping a ZFS-on-root and the like.
#
# -- Yarema
#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#
program=`basename $0`
if [ -f "$0.rc" ];then
. "$0.rc"
fi
: ${KMEMSIZE:="512M"}
: ${RELEASE:="7.0-RELEASE"}
: ${DESTDIR:="/media"}
if [ $# -lt 1 ]; then
echo "Usage: ${program} "
echo " where is the path to the distribution"
echo " files, usually an .iso mounted on /dist"
echo " and is usually da0"
exit 1
fi
dist="$1"
vdev="$2"
#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#
ask() {
local question default answer
question=$1
default=$2
read -p "${question} [${default}]? " answer
if [ -z "${answer}" ]; then
answer=${default}
fi
echo ${answer}
}
yesno() {
local question default answer
question=$1
default=$2
while :; do
answer=$(ask "${question}" "${default}")
case "${answer}" in
[Yy]*) return 0;;
[Nn]*) return 1;;
esac
echo "Please answer yes or no."
done
}
#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#
if yesno "Create one slice covering the entire ${vdev}" n; then
dd if=/dev/zero of=/dev/${vdev} bs=512 count=79
fdisk -BIv /dev/${vdev}
fi
if yesno "Initialize the BSD label" y; then
bsdlabel -wB /dev/${vdev}s1
fi
bsdlabel /dev/${vdev}s1
while yesno "(Re)Edit the BSD label" n; do
bsdlabel -e /dev/${vdev}s1
bsdlabel /dev/${vdev}s1
done
newfs -U /dev/${vdev}s1a
[ -d ${DESTDIR} ] || mkdir -p ${DESTDIR}
mount /dev/${vdev}s1a ${DESTDIR}
#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#
: ${dists:="base games manpages info dict"}
for i in ${dists}; do
echo " Extracting the ${i} distribution into ${DESTDIR}..."
cat ${dist}/${RELEASE}/${i}/${i}.?? | tar --unlink -xpzf - -C ${DESTDIR}
done
echo " Extracting the GENERIC kernel into ${DESTDIR}/boot/"
cat ${dist}/${RELEASE}/kernels/generic.?? | tar --unlink -xpzf - -C ${DESTDIR}/boot && ln -f ${DESTDIR}/boot/GENERIC/* ${DESTDIR}/boot/kernel/
echo " Copying ${dist}/${RELEASE}/ to ${DESTDIR}..."
tar cf - ${dist}/${RELEASE}/* | tar --unlink -xpf - -C ${DESTDIR}
# Mounting /var on tmpfs will work for both tmp directories
# by creating a softlink from /tmp to /var/tmp
rm -rf ${DESTDIR}/tmp
ln -sf var/tmp ${DESTDIR}/tmp
#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#
if [ -f $0.local ];then
. $0.local
fi
#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#
echo "vm.kmem_size=\"${KMEMSIZE}\" # Sets the size of kernel memory (bytes)" >> ${DESTDIR}/boot/loader.conf.local
echo "vm.kmem_size_max=\"${KMEMSIZE}\" # used by in-kernel malloc(9)" >> ${DESTDIR}/boot/loader.conf.local
echo "nullfs_load=\"YES\" # Null filesystem" >> ${DESTDIR}/boot/loader.conf.local
echo "zfs_load=\"YES\" # ZFS" >> ${DESTDIR}/boot/loader.conf.local
echo "geom_eli_load=\"YES\" # Disk encryption driver (see geli(8))" >> ${DESTDIR}/boot/loader.conf.local
echo "geom_mirror_load=\"YES\" # RAID1 disk driver (see gmirror(8))" >> ${DESTDIR}/boot/loader.conf.local
${EDITOR:-"vi"} ${DESTDIR}/boot/loader.conf.local
#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#
echo "# Device Mountpoint FStype Options Dump Pass#" > ${DESTDIR}/etc/fstab
echo "/dev/${vdev}s1a / ufs rw,noatime 0 0" >> ${DESTDIR}/etc/fstab
echo "tmpfs /var tmpfs rw,nosuid 0 0" >> ${DESTDIR}/etc/fstab
echo "proc /proc procfs rw 0 0" >> ${DESTDIR}/etc/fstab
echo "# Device Mountpoint FStype Options Dump Pass#" >> ${DESTDIR}/etc/fstab
echo "/dev/acd0 /cdrom cd9660 ro,nodev,noauto,nosuid 0 0" >> ${DESTDIR}/etc/fstab
echo "/dev/fd0 /media/fd ufs rw,nodev,noauto,nosuid 0 0" >> ${DESTDIR}/etc/fstab
echo "/dev/fd0 /media/floppy msdosfs rw,nodev,noauto,nosuid 0 0" >> ${DESTDIR}/etc/fstab
${EDITOR:-"vi"} ${DESTDIR}/etc/fstab
#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#
umount /dev/${vdev}s1a
#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#
# EOF
Implementation
The zfsboot script presented here will create the regular bootable
'a' partition, but configure it as RAID-1 using
.
This approach provides the possibility to directly boot from any of the
drives by configuring the BIOS boot order. This works even if only
one drive is used, although
will not be doing any mirroring. See Ralf S. Engelschall's
<> excellent
and note the implementation here is using GEOM mirror on partitions of
a slice on a disk for the boot partition.
Since we're forced to use a regular 'a' boot partition there is some
advntage in using a regular 'b' partion for swap. Due to the way ZFS
is currently implemented there is a known issue (in FreeBSD and
OpenSolaris) where ZFS needs to allocate memory to send an I/O request.
When there is no memory, ZFS cannot allocate any and thus cannot swap
a process out and free it. Such low memory conditions can cause the
machine to effectively freeze — unable to swap out to disk right
when it is most crucial to do so. See
http://Lists.FreeBSD.org/pipermail/freebsd-current/2007-September/076831.html
The script assumes the FreeBSD 7 disk1 ISO to be mounted on /dist on
another host and /root/.ssh/authorized_keys on that host should allow
the target machine booted via the USB drive to connect without
requiring a password.
#!/bin/sh
#
# HOWTO/script to create a ZFS pool mounted as an almost bootable "root"
# partition.
#
# Adapted by Yarema from
# ~rse/mirror/
#
#
# TuningGuide
#
# This script will create a 512M gmirror(8) boot partition.
# A swap 'b' partition on each drive if more than one is used.
# And a 'd' partition for the zpool.
# When using more than one drive the zpool can be 'mirror'.
# When using three or more drives the zpool type can be 'raidz'.
#
# The gmirror(8) boot partition will be mounted to the /strap mountpoint
# on the zpool. /strap/boot will be nullfs mounted to the /boot mountpoint.
# /strap/rescue will be nullfs mounted to the /rescue mountpoint.
# /strap/bin and /strap/sbin will be soft-linked to /rescue.
#
# Normally even single user boot will still mount the zfs as root.
# Putting the statically linked /rescue utilities on the boot/'a'
# partition seems like a good idea in the unlikely case that the zpool
# is unmountable. Albeit zpool(1M) and zfs(1M) are not (yet?) built or
# installed in /rescue.
#
# WARNING: Due to the way ZFS is currently implemented there is a known
# issue (in FreeBSD and OpenSolaris) where ZFS needs to allocate memory
# to send an I/O request. When there is no memory, ZFS cannot allocate
# any and thus cannot swap a process out and free it. Such low memory
# conditions can cause the machine to effectively freeze -- unable to
# swap out to disk right when it is most crucial to do so.
# http://Lists.FreeBSD.org/pipermail/freebsd-current/2007-September/076831.html
#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#
program=`basename $0`
if [ $# -lt 1 ]; then
echo "Usage: ${program} [mirror|raidz] ..."
exit 1
fi
case "$1" in
mirror|raidz|raidz[12])
type="$1"; shift
if [ "${type}" = 'mirror' -a $# -lt 2 ]; then
echo "Usage: ${program} ${type} ..."
exit 1
elif [ "${type}" = 'raidz2' -a $# -lt 4 ]; then
echo "Usage: ${program} ${type} ..."
exit 1
elif [ "${type}" != 'mirror' -a $# -lt 3 ]; then
echo "Usage: ${program} ${type} ..."
exit 1
fi
;;
esac
vdev1="$1"
vdevs="$@"
#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#
if [ -f "$0.rc" ];then
. "$0.rc"
fi
# The recommended name is simply the letter 'z' which makes output
# form mount(8), zfs(8M) and zpool(8M) easy to read for us humans.
: ${POOL:='z'}
DESTDIR="/${POOL}"
# file describing the ZFS datasets to create
: ${DATASETS:="$0.fs"}
# FreeBSD release directory to install from
: ${RELEASE:="7.0-RELEASE"}
# Server hostname to net install from
: ${SERVER:="server"}
# Kernel tunables as per TuningGuide
: ${KMEMSIZE:="512M"}
# Maximum installed Megabytes of RAM the system is likely to have.
# Used for calculating the size of the swap partision(s).
if [ -z "${MAXRAM}" ]; then
MAXRAM=$(expr $(expr $(sysctl -n hw.physmem) / 1024 / 1024 / 1024 + 1) \* 1024)
fi
# When setting up a single drive set swapsize to double the ${MAXRAM}
# With more than one drive swap will be striped across all drives
# effectively making it ${MAXRAM} times the number of drives.
if [ "${vdev1}" = "${vdevs}" ];then
swapsize=$(expr ${MAXRAM} \* 2)
else
swapsize=${MAXRAM}
fi
#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#
ask() {
local question default answer
question=$1
default=$2
read -p "${question} [${default}]? " answer
if [ -z "${answer}" ]; then
answer=${default}
fi
echo ${answer}
}
yesno() {
local question default answer
question=$1
default=$2
while :; do
answer=$(ask "${question}" "${default}")
case "${answer}" in
[Yy]*) return 0;;
[Nn]*) return 1;;
esac
echo "Please answer yes or no."
done
}
#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#
if yesno "Create one slice covering the entire disk(s)" n; then
{ # Wipe out any prior zpool, gmirror, fdisk and bsdlabel meta data.
umount ${DESTDIR}/strap/boot
umount ${DESTDIR}/strap/rescue
umount ${DESTDIR}/strap
zpool destroy ${POOL}
rm -f /boot/zfs/zpool.cache
eval "gmirror remove -v boot `echo ${vdevs} | sed -E 's/[[:<:]][[:alnum:]]+[[:>:]]/&s1a/g'`"
} > /dev/null 2>&1
for d in ${vdevs}; do
dd if=/dev/zero of=/dev/${d} bs=32m count=17
fdisk -BIv /dev/${d}
done
fi
if yesno "Initialize the BSD label" y; then
for d in ${vdevs}; do
bsdlabel -wB /dev/${d}s1
done
fi
# Create a bsdlabel where the 'a' bootable partition is 512M plus one
# extra sector for gmirror metadata. The default /boot directory with a
# FreeBSD 7.0 GENERIC kernel and all the modules takes up about 178MB.
# 256MB can be a little tight if you need to keep a backup kernel or two.
# 512MB is still a good size for the boot partition.
#
# Create a large enough 'b' swap partition to be used for a swap backed
# /tmp mdmfs, /usr/obj mdmfs, and/or any other partitions you do not care
# to keep between reboots which might benefit from the extra speed of mfs.
# According to zfs(1M), using a ZFS volume as a dump device is not supported.
# Setting 'dumpdev' to the swap partition requires that it be at least as
# big as the installed RAM. When setting up a single drive, the swapsize
# will default to double the maximum installed RAM the system is likely to
# have plus what's left from rounding the 'd' partition down to the nearest
# Gigabyte. With more than one drive swap will be striped across all drives
# and only needs to be as large on each drive as the installed RAM so that
# a coredump can fit.
#
# Allocate the 'd' partition to be used by the "root" ZFS pool rounded down to
# the nearest Gigabyte with the remainder going to the 'b' swap partition.
bsdlabel /dev/${vdev1}s1 | awk -v s=${swapsize} '
/^ +c: / {
a = 512 * 1024 * 2 + 1
b = s * 1024 * 2
c = $2
d = c - 16 - a - b
}
END {
print "8 partitions:"
print "# size offset fstype"
printf(" a: %d 16 4.2BSD\n", a)
print " b: * * swap"
print " c: * 0 unused"
printf(" d: %dG * unused\n", d / 2 / 1024 / 1024 )
}
' - > /tmp/bsdlabel.txt
bsdlabel -R /dev/${vdev1}s1 /tmp/bsdlabel.txt
bsdlabel /dev/${vdev1}s1
while yesno "(Re)Edit the BSD label" n; do
bsdlabel -e /dev/${vdev1}s1
bsdlabel /dev/${vdev1}s1
done
bsdlabel /dev/${vdev1}s1 > /tmp/bsdlabel.txt
if yesno "Apply the same BSD label to all mirrored devices" y; then
for d in ${vdevs}; do
bsdlabel -R /dev/${d}s1 /tmp/bsdlabel.txt
done
fi
# Create a gmirror of the 'a' partition across all the devices
eval "gmirror label -v -h -b load boot `echo ${vdevs} | sed -E 's/[[:<:]][[:alnum:]]+[[:>:]]/&s1a/g'`"
#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#===#
if yesno "Create the ZFS pool on the 'd' partition(s)" y; then
eval "zpool create ${POOL} ${type} `echo ${vdevs} | sed -E 's/[[:<:]][[:alnum:]]+[[:>:]]/&s1d/g'`"
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