#!/bin/sh

# quick and dirty script for checking dates of zfs snapshots and removing old snapshots
# achtung, this is made with FreeBSD's `date', won't work with gnuuuu and other `date's...
# rev 1.5 lopez@yellowspace.net 11.12.2007 

# abstract:
# given pool $POOL, check if available space is less than $MINSPACE.
# If yes, remove snapshots $KEEPTIME days older than the newest one

MINSPACE=20 # in GigaBytes
KEEPTIME=15 # in days
POOL="zentank"

giveStamp() {
	/bin/date -j -f "%a %b %d %T %Z %Y" "$1" "+%s"
}

removeSnap() {
	if [ "$3" = "-v" ] ; then echo "Removing $1, it is old, made on $2"; fi
	snaponly=`echo "$1" | /usr/bin/egrep -c '@.+'`
	if [ $snaponly -gt 0 ] ; then
		/sbin/zfs destroy "$1"
	else
		echo "$1 is not a valid snapshot name, dont destroy your pool! *g*"
		exit 1
	fi
}

# see how many gigs are available

availgigs=`/sbin/zfs list -H -o available $POOL | /usr/bin/tr 'G' ' '`

if [ $availgigs -gt $MINSPACE ] ; then
	if [ "$1" = "-v" ] ; then echo "$availgigs GB available, $MINSPACE required, no need to delete"; fi
	exit 0
fi

# get the timestamp of the newest snapshot
# damned list verb does not accept a pool name with -t snapshot

lastsnapdate=`/sbin/zfs list -t snapshot -H -o name,creation -s creation | \
	/usr/bin/egrep "^${POOL}" | \
	/usr/bin/cut -f 2 | \
	/usr/bin/tail -n 1`
	
lastsnapstamp=`giveStamp "$lastsnapdate"`

subtrsec=$((KEEPTIME*86400))
minstamp=$((lastsnapstamp-subtrsec))
# minstamp=`/bin/date -j -v -${KEEPTIME}d +%s` # older than KEEPTIME from now

removedsomething=0
/sbin/zfs list -t snapshot -H -o name,creation -s name | /usr/bin/egrep "^${POOL}" | while read snapname snapdate ; do
	if [ "$1" = "-v" ] ; then echo "Name: $snapname, Date is $snapdate"; fi
	stamp=`giveStamp "$snapdate"`
	if [ $stamp -lt $minstamp ] ; then
		removeSnap "$snapname" "$stamp" "$1"
		removedsomething=1
	fi
done

if [ $removedsomething -eq 0 ] ; then
	echo -n "WARNING: $0 did not find snapshots of $POOL older than $KEEPTIME days, "
	echo "yet available space is $availgigs, which is below $MINSPACE."
	exit 1
fi

exit 0