A script for creating/rotating snapshots of LVM volumes via (ana)cron

lvtimesnap.sh

#!/usr/bin/env bash
#
# Creating and rotating snapshots of LVM volumes
#
# https://gist.github.com/SmartFinn/013dc2670f6605826acfae8e25c11178
#
# Copyright (c) 2023 Serhii Yeremenko (https://github.com/SmartFinn)
#
# Permission to use, copy, modify, and/or distribute this software for any
# purpose with or without fee is hereby granted.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
# REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
# AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
# INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
# LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
# OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
# PERFORMANCE OF THIS SOFTWARE.

set -eu -o pipefail

readonly PROGNAME="$(basename "${BASH_SOURCE[0]}" .sh)"
readonly VERSION="0.0.3"

msg() {
	printf "%s: %s\n" "$PROGNAME" "$*"
}

err() {
	printf "%s: Error: %s\n" "$PROGNAME" "$*" >&2
}

usage() {
	cat <<- EOF
	usage:
	 $PROGNAME [options] LogicalVolumePath...

	OPTIONS:
	 -l LogicalExtentsNumber[%{VG|PVS|FREE|ORIGIN}]
	      Default value: 100%ORIGIN
	      Gives the number of logical extents to allocate for
	      the new logical volume.
	      See lvcreate(8) for details.
	 -L LogicalVolumeSize[b|B|s|S|k|K|m|M|g|G|t|T|p|P|e|E]
	      Gives  the size to allocate for the new logical volume.
	      Default unit is megabytes.
	      See lvcreate(8) for details.
	 -N NumberOfSnapshots
	      Default value: 2
	      Specify how many of the last snapshots to keep.
	 -D   Delete all snapshots of the specified logical volume.
	 -V   print $PROGNAME version and exit
	 -h   show this help
	EOF

	exit "${1:-0}"
}

create_snapshot() {
	local snap_name="${1?snap_name is required}"
	local lv_path="${2?lv_path is required}"

	[ "$DO_NOT_CREATE" -eq 0 ] || return 0

	sync

	lvcreate "${SNAP_SIZE[@]}" --snapshot --name "$snap_name" "$lv_path"
}

clear_snapshots() {
	local lv_name="${1?lv_name is required}"
	local snap_prefix="${2?no prefix is specified}"
	local -i snap_count
	local -i excess_snaps
	local -a snapshots=()

	read -ra snapshots < <(lvs --noheadings -o lv_path -S "origin=$lv_name" \
		-S 'lv_attr=~^s' -S "lv_name=~^$snap_prefix" | xargs)

	snap_count=${#snapshots[@]}
	excess_snaps=$(( snap_count - KEEP ))

	for (( i=0; i < excess_snaps; i++ )); do
		[ -n "${snapshots[$i]}" ] || continue
		lvremove --force "${snapshots[$i]}"
	done
}

declare -a SNAP_SIZE=(-l 100%ORIGIN)
declare -i KEEP=2
declare -i DO_NOT_CREATE="${DO_NOT_CREATE:-0}"

while getopts ":DL:l:N:Vh" opt; do
	case "$opt" in
		D ) DO_NOT_CREATE=1
			KEEP=0
			;;
		L | \
		l ) SNAP_SIZE=("-$opt" "$OPTARG") ;;
		N ) KEEP="$OPTARG" ;;
		V ) printf "%s %s\n" "$PROGNAME" "$VERSION"
			exit 0
			;;
		h ) usage 0 ;;
		: ) err "option requires an argument -- '-$OPTARG'"
			usage 2
			;;
		\?) err "illegal option -- '-$OPTARG'"
			usage 2
			;;
	esac
done

shift $((OPTIND-1))

# Return an error if positional parameters are not found
if [ -z "${1:-}" ]; then
	err "no logical volume is specified"
	usage 2
fi

for lvol in "$@"; do
	unset LVM2_LV_NAME LVM2_LV_PATH

	eval "$(lvs --noheadings --nameprefixes -o lv_name,lv_path "$lvol")"

	[ -b "$LVM2_LV_PATH" ] || exit 1

	timestamp="$(date +%Y%m%d_%H%M%S)"
	snap_prefix="${LVM2_LV_NAME}_snap_"
	snap_name="${snap_prefix}${timestamp}"

	create_snapshot "$snap_name" "$LVM2_LV_PATH"
	clear_snapshots "$LVM2_LV_NAME" "$snap_prefix"
done

Hi, thanks for sharing your script 👍

Just one thing, your options are wrong:

	OPTIONS:
	 -L LogicalExtentsNumber[b|B|s|S|k|K|m|M|g|G|t|T|p|P|e|E]
              Default unit is megabytes.
	      Gives the number of logical extents to allocate for
	      the new logical volume.
	      See lvcreate(8) for details.
	 -l LogicalVolumeSize[%{VG|PVS|FREE|ORIGIN}]
	      Gives  the size to allocate for the new logical volume.
	      Default value: 100%ORIGIN
	      See lvcreate(8) for details.
	 -N NumberOfSnapshots

Took me some reading through lvcreate so see why it wasn't working on my side :P !

@KalyaSc Thanks for pointing that. I have swapped the options.