XigmaNAS

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#!/bin/sh
#############################################################################
# Purge old snapshots
# Usage: ./zpurge.sh filesystem
# Author: Erik Kaashoek
#############################################################################

secondsinminute=60
minute=1
hour=$(($minute*60))
halfhour=$(($minute*30))
day=$(($hour*24))
halfday=$(($hour*12))
week=$(($day*7))
halfweek=$(($day*3))
month=$(($week*4))
halfmonth=$(($week*2))
quarter=$(($month*3))
halfquarter=$(($month*1))
year=$(($quarter*4))
halfyear=$(($quarter*2))

#define snapshot spacing grid
maxquarters=$((16*$quarter))
quartergap=$(($quarter-$halfmonth))
maxmonths=$((5*$month)) 
monthgap=$(($month - $halfweek))
maxweeks=$((6*$week))
weekgap=$(($week-$halfday))
maxdays=$((9*$day))
daygap=$(($day-$halfhour))
maxhours=$((26*$hour))
hourgap=$(($hour - $minute))
maxminutes=$((70*$minute))

TAG="auto"

usage() {
    echo "Usage: $(basename $0) [ -n ] [ -v ] [ -t tag ] pool"
    echo "  -n    debug (dry-run) mode"
    echo "  -v    verbose mode"
    echo "  -t    specify part of snapshot tag, default=auto"
    exit 1
}

DEBUG=""
VERBOSE=""
if [ "$1" == "-v" ] ; then
	VERBOSE=1 ; shift
fi
if [ "$1" == "-n" ] ; then
	DEBUG=1 ; shift
fi
if [ "$1" == "-v" ] ; then
	VERBOSE=1 ; shift
fi
if [ "$1" == "-t" ] ; then
	TAG="$2"
	shift ; shift ;
fi
if [ $# -ne 1 ]; then 
	usage
fi

purgeSnapshot()
{
#	echo "Purge $1 because $2"
    if [ $DEBUG ]; then
		echo "would run: zfs destroy $1 # because $2"
    else
		[ "$VERBOSE" ] && echo  "running: zfs destroy $1 # because $2"
		zfs destroy $1
	fi
}

readonly fs=$1

[ "$VERBOSE" ] && echo "Purge snapshots from $fs with pattern $quarter, $month, $week, $day, $hour and tag=$TAG"

if zfs list -H -o name| grep "$fs">/dev/null; then
	[ "$VERBOSE" ] && echo "Filesystem \"$fs\" does exist"
else
	echo "Filesystem \"$fs\" does not exist"
	return 0
fi

#get current time once to ensure equal spacing
now=`date +"%s"` 
#to ensure oldest snapshot only gets deleted when it is older then maxquarters
prevage=$now

#Loop through all snapshots, oldest first, and calculate age and gap with next older existing snapshot
zfs list -Hr -t snapshot -o name,creation -s creation  $fs | grep $TAG | while read snap creation; do
	age=$((($now -  `date -j -f "%a %b %d %H:%M %Y" "$creation" +"%s"` ) / $secondsinminute ))
	gap=$(($prevage - $age))
		
#	echo "$snap ( $prevage, $age, $gap)"
#	Purge if older then maxquarters
	if [ $age -gt $maxquarters ]; then	
		purgeSnapshot "$snap" "old"
# Or purge if older then maxmonths and too frequent
	elif [ $age -gt $maxmonths -a  $gap -lt $quartergap ]; then
		purgeSnapshot "$snap" "quarter"
# Or purge if older then maxweeks and too frequent
	elif [ $age -gt $maxweeks -a  $gap -lt $monthgap ]; then 
		purgeSnapshot "$snap" "month"
# Or purge if older then maxdays and too frequent
	elif [ $age -gt $maxdays -a $gap -lt $weekgap ]; then
		purgeSnapshot "$snap" "week"
# Or purge if older then maxhours and too frequent
	elif [ $age -gt $maxhours -a $gap -lt $daygap ]; then
		purgeSnapshot "$snap" "day"
# Or purge if older then maxminutes and too frequent
	elif [ $age -gt $maxminutes -a $gap -lt $hourgap ]; then
		purgeSnapshot "$snap" "hour" 
	else
		[ "$VERBOSE" ] &&  echo "Keep $snap ( $prevage, $age, $gap)"
		prevage=$age
		prevsnap=$snap
	fi
done

exit 0