/usr/bin/rsbackup-snapshot-hook

#! /bin/sh
#
# Copyright © 2012, 2014, 2015 Richard Kettlewell.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
set -e

SNAPS=/snap
DIVISOR=5

# By default LVM whines about any FDs it doesn't know about
export LVM_SUPPRESS_FD_WARNINGS=1

x() {
  fatal_errors=true
  case "$1" in
  +e )
    shift
    fatal_errors=false
    ;;
  esac

  echo "HOOK: EXEC:" "$@" >&2
  if $fatal_errors; then
    "$@"
  else
    set +e
    "$@"
    status=$?
    set -e
  fi
}

while [ $# -gt 0 ]; do
  case "$1" in
  --help | -h )
    cat <<EOF
Usage:
  rsbackup-snapshot-hook [OPTIONS]

Options:
  --snaps, -s PATH       Snapshot directory path (${SNAPS})
  --divisor, -d DIVISOR  How much smaller snapshot can be (${DIVISOR})
  --help, -h             Display usage message
  --version, -V          Display version string

This script is intended to be run as an rsbackup pre/post-backup hook,
not interactively.
EOF
    exit 0
    ;;
  -s | --snaps )
    shift
    SNAPS="$1"
    shift
    ;;
  -d | --divisor )
    shift
    DIVISOR="$1"
    shift
    ;;
  -V | --version )
    echo "rsbackup-snapshot-hook 3.0"
    exit 0
    ;;
  * )
    echo "ERROR: unknown option '$1'" >&2
    exit 1
    ;;
  esac
done

# The path where the snapshot will be mounted
snap=$SNAPS/$RSBACKUP_VOLUME

# How to execute commands on the host
case $RSBACKUP_SSH_TARGET in
localhost )
  remote=""
  ;;
* )
  remote="ssh $RSBACKUP_SSH_TARGET"
  ;;
esac

# Only use snapshots if configured to do so
if ${RSBACKUP_ACT:-false} && $remote test -e $snap; then
  # Identify the device name
  devname=$($remote df ${RSBACKUP_VOLUME_PATH}|awk '/^\// { print $1}')
  # Canonicalize the device name
  dev=""
  for alias in $(x $remote udevadm info -rqsymlink -n "$devname"); do
    case "$alias" in
    /dev/mapper/* )
      dev="${alias}"
      break
      ;;
    esac
  done
  if [ "${dev}" =  "" ]; then
    echo >&2 "ERROR: cannot parse device name $device"
    exit 1
  fi
  lv=${dev#*-}
  snaplv=${lv}.snap
  snapdev=${dev%-*}-${snaplv}
  case ${RSBACKUP_HOOK} in
  pre-backup-hook )
   # Tidy up any leftovers
   if $remote [ -e $snapdev ]; then
     x $remote umount $snap >&2 || true
     x $remote lvremove --force $snapdev >&2 || true
   fi
   # Find out the size of the source volume
   lvsz=$($remote lvdisplay $dev | awk '/Current LE/ { print $3 }')
   lvname=$($remote lvdisplay $dev | awk '/LV Path/ { print $3 }')
   if [ "$lvname" = "" ]; then
     lvname=$($remote lvdisplay $dev | awk '/LV Name/ { print $3 }')
   fi
   snaplvsz=$(($lvsz / $DIVISOR))
   # Create and mount the snapshot
   x $remote lvcreate --extents $snaplvsz --name $snaplv --snapshot $lvname >&2
   # Snapshots may need fscking before mounting
   # fsck status is a bitmap; 1 means that errors were corrected.
   # All the other nonzero bits are fatal.
   x +e $remote fsck -a $snapdev >&2
   case $status in
   0 | 1 )
     ;;
   * )
     x $remote lvremove --force $snapdev >&2
     exit $status
     ;;
   esac
   x $remote mount -o ro $snapdev $snap >&2
   # Backup from the snapshot, not the master
   echo $snap
   ;;
  post-backup-hook )
   # Tidy up
   x $remote umount $snap >&2
   x $remote lvremove --force $snapdev >&2
   ;;
  esac
fi
rsbackup 3.0-2 / usr / bin / rsbackup-snapshot-hook
