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#!/bin/bash
# zfs-snap-prune - Prune old ZFS snapshots with hybrid retention policy
#
# Retention Policy:
# - Always keep the N most recent snapshots (default: 20)
# - Delete snapshots beyond N only if older than MAX_AGE (default: 180 days)
# - Never delete genesis snapshot
#
# Usage:
# zfs-snap-prune [OPTIONS]
#
# Options:
# --dry-run Show what would be deleted without deleting
# --verbose Show decision for every snapshot
# --quiet Suppress non-error output
# --test Use mock data from stdin instead of real ZFS
# --help Show this help message
#
# Environment variables:
# POOL_NAME - ZFS pool name (default: zroot)
# ROOT_DATASET - Root dataset path (default: ROOT/default)
# KEEP_COUNT - Number of recent snapshots to always keep (default: 20)
# MAX_AGE_DAYS - Delete older snapshots beyond KEEP_COUNT (default: 180)
# NOW_OVERRIDE - Override current timestamp for testing (epoch seconds)
set -e
# Configuration (can be overridden by environment)
POOL_NAME="${POOL_NAME:-zroot}"
ROOT_DATASET="${ROOT_DATASET:-ROOT/default}"
KEEP_COUNT="${KEEP_COUNT:-20}"
MAX_AGE_DAYS="${MAX_AGE_DAYS:-180}"
FULL_DATASET="${POOL_NAME}/${ROOT_DATASET}"
# Flags
DRY_RUN=false
VERBOSE=false
QUIET=false
TEST_MODE=false
# Colors for output
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
BLUE='\033[0;34m'
NC='\033[0m'
usage() {
sed -n '2,/^$/p' "$0" | sed 's/^# \?//'
exit 0
}
info() {
[[ "$QUIET" == "true" ]] && return
echo -e "${GREEN}[INFO]${NC} $1"
}
verbose() {
[[ "$VERBOSE" != "true" ]] && return
echo -e "${BLUE}[VERBOSE]${NC} $1"
}
warn() {
[[ "$QUIET" == "true" ]] && return
echo -e "${YELLOW}[WARN]${NC} $1"
}
error() {
echo -e "${RED}[ERROR]${NC} $1" >&2
exit 1
}
# Parse arguments
while [[ $# -gt 0 ]]; do
case "$1" in
--dry-run)
DRY_RUN=true
shift
;;
--verbose)
VERBOSE=true
shift
;;
--quiet)
QUIET=true
shift
;;
--test)
TEST_MODE=true
shift
;;
--help|-h)
usage
;;
*)
error "Unknown option: $1"
;;
esac
done
# Check if running as root (skip in test mode)
if [[ "$TEST_MODE" != "true" ]] && [[ $EUID -ne 0 ]]; then
error "This script must be run as root"
fi
# Get current timestamp (can be overridden for testing)
NOW="${NOW_OVERRIDE:-$(date +%s)}"
MAX_AGE_SECONDS=$((MAX_AGE_DAYS * 24 * 60 * 60))
CUTOFF_TIME=$((NOW - MAX_AGE_SECONDS))
info "Pruning snapshots for ${FULL_DATASET}"
info "Policy: Keep ${KEEP_COUNT} recent, delete if older than ${MAX_AGE_DAYS} days"
[[ "$DRY_RUN" == "true" ]] && info "DRY RUN - no changes will be made"
# Get snapshots - either from ZFS or stdin (test mode)
# Expected format: snapshot_name<TAB>creation_date_string
# Example: zroot/ROOT/default@pre-pacman_2025-01-15 Wed Jan 15 10:30 2025
if [[ "$TEST_MODE" == "true" ]]; then
# Read mock data from stdin
SNAPSHOTS=$(cat | tac)
else
# Query real ZFS - sorted by creation (oldest first), then reversed for newest first
SNAPSHOTS=$(zfs list -H -t snapshot -o name,creation -s creation -r "$FULL_DATASET" 2>/dev/null | \
grep "^${FULL_DATASET}@" | \
tac) || true
fi
if [[ -z "$SNAPSHOTS" ]]; then
info "No snapshots found"
exit 0
fi
# Count snapshots
TOTAL=$(echo "$SNAPSHOTS" | wc -l)
info "Found ${TOTAL} snapshots"
# Track results
DELETED=0
KEPT=0
POSITION=0
# Process each snapshot
while IFS=$'\t' read -r snapshot creation_str; do
[[ -z "$snapshot" ]] && continue
POSITION=$((POSITION + 1))
SNAP_NAME="${snapshot##*@}"
# Parse creation time
if [[ "$TEST_MODE" == "true" ]]; then
# In test mode, creation_str is epoch seconds
SNAP_TIME="$creation_str"
else
# In real mode, parse date string
SNAP_TIME=$(date -d "$creation_str" +%s 2>/dev/null || echo "0")
fi
AGE_DAYS=$(( (NOW - SNAP_TIME) / 86400 ))
# Decision logic
if [[ $POSITION -le $KEEP_COUNT ]]; then
# Always keep the first KEEP_COUNT snapshots (most recent)
verbose "KEEP: ${SNAP_NAME} (position ${POSITION}/${KEEP_COUNT}, ${AGE_DAYS} days old) - within keep count"
KEPT=$((KEPT + 1))
elif [[ "$SNAP_NAME" == "genesis" ]]; then
# Never delete genesis
verbose "KEEP: ${SNAP_NAME} (position ${POSITION}, ${AGE_DAYS} days old) - genesis protected"
KEPT=$((KEPT + 1))
elif [[ $SNAP_TIME -ge $CUTOFF_TIME ]]; then
# Not old enough to delete
verbose "KEEP: ${SNAP_NAME} (position ${POSITION}, ${AGE_DAYS} days old) - younger than ${MAX_AGE_DAYS} days"
KEPT=$((KEPT + 1))
else
# Delete: beyond keep count AND older than max age
if [[ "$DRY_RUN" == "true" ]]; then
info "WOULD DELETE: ${SNAP_NAME} (position ${POSITION}, ${AGE_DAYS} days old)"
DELETED=$((DELETED + 1))
elif [[ "$TEST_MODE" == "true" ]]; then
# Test mode: simulate deletion (don't actually call zfs)
verbose "DELETE: ${SNAP_NAME} (position ${POSITION}, ${AGE_DAYS} days old)"
DELETED=$((DELETED + 1))
else
verbose "DELETE: ${SNAP_NAME} (position ${POSITION}, ${AGE_DAYS} days old)"
if zfs destroy "$snapshot" 2>/dev/null; then
DELETED=$((DELETED + 1))
else
warn "Failed to delete ${snapshot}"
fi
fi
fi
done <<< "$SNAPSHOTS"
# Summary
info "Summary: ${KEPT} kept, ${DELETED} deleted"
# Regenerate GRUB menu if we deleted anything (skip in dry-run and test modes)
if [[ $DELETED -gt 0 ]] && [[ "$DRY_RUN" != "true" ]] && [[ "$TEST_MODE" != "true" ]]; then
if [[ -x /usr/local/bin/grub-zfs-snap ]]; then
info "Regenerating GRUB menu..."
/usr/local/bin/grub-zfs-snap
fi
fi
# Exit with special code for testing (number of deleted)
if [[ "$TEST_MODE" == "true" ]]; then
echo "RESULT:kept=${KEPT},deleted=${DELETED}"
fi
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