#!/bin/bash
# $Id: zfs-backup,v 1.6 2016/07/03 00:54:07 friedman Exp $

# To initialize iscsi target on freebsd:
#	iscsictl -A -d wdmc-1.prv.splode.com
#	iscsictl -A -d obey-chomsky.prv.splode.com
#
# To bring iscsi backup pool online:
# 	zpool import [poolname]
#
# To take offline on freebsd:
# 	zpool export [poolname]
#	iscsictl -R -p obey-chomsky.prv.splode.com


# latest (most recent) common snapshot
oldsnap()
{
    srcpool=${1%%@*}
    dstpool=${2%%@*}

    zfs list -t snapshot -H -d 1 -o name -S name $srcpool |
        while read snap; do
            snap=${snap##*@}
            if zfs list $dstpool@$snap > /dev/null 2>&1; then
                echo $snap
                return 0
            fi
        done
    return 1
}

newsnap()
{
    case $1 in
        *@* ) newsnap=${1#*@}
              if ! fslist $srcpool@$newsnap > /dev/null 2>&1; then
                  echo Snapshot $srcpool@$newsnap does not exist. 1>&2
                  return 1
              fi ;;

        *   ) newsnap=`mksnap $srcpool` ;;
    esac

    echo $newsnap
}

mksnap()
{
    name=backup.`date +"%Y-%m-%d.%H:%M:%S"`
    zfs snapshot -r $1@$name
    echo $name
}

fslist()
{
    zfs list -H -r -o name "$@"
}

backup()
{
    srcpool=${1%%@*}
    dstpool=$2

    newsnap=`newsnap $1`
    case $newsnap in '' ) return 1 ;; esac

    oldsnap=`oldsnap $srcpool $dstpool`
    case $oldsnap in
        $newsnap ) echo "Both pools already have snapshot $oldsnap" 1>&2
                   return 0 ;;
    esac

    for fs in `fslist $srcpool`; do
        date +"[%Y-%m-%d %H:%M:%S%z] Backing up $fs"
        time { zfs send -e ${oldsnap:+-I $oldsnap} $fs@$newsnap | zfs recv -F -v -d $dstpool; }
    done
    date +"[%Y-%m-%d %H:%M:%S%z] Done."
}

mirror()
{
    srcpool=${1%@*}
    dstpool=$2

    newsnap=`newsnap $1`
    case $newsnap in '' ) return 1 ;; esac

    date +"[%Y-%m-%d %H:%M:%S%z] Mirroring $srcpool@$newsnap to $dstpool"
    zfs send -e -R $srcpool@$newsnap | zfs recv -F -v -d $dstpool
    date +"[%Y-%m-%d %H:%M:%S%z] Done."
}

main()
{
    PATH=/sbin:$PATH

    case $#:$3 in
        2:      ) backup "$@" ;;
        3:-full ) mirror "$@" ;;
        *       ) echo "Usage: ${0##*/} [srcpool] [dstpool]" 1>&2
                  exit 1 ;;
    esac
}

main "$@"

# eof