Packaging a Sample Cron Script

[sentry0]

Is there any interest in a simple bash script that can be installed as a cron?

This is highly subjective to the number of VMs you have, the space available, etc. I use a script that provides me with 2-6 weeks of backups, which is suitable for my personal needs.

Here is the script I use as a cron;

#!/usr/bin/env bash
#
# vm-snapshot.sh
# Copyright (C) 2024  Sentry0
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.
# 
# ---
#
# Will perform an incremental backup (if possible) of a running or stopped VM 
# and deposit it into a monthly backup directory.  On the 15th of the current 
# month, the previous months' snapshots are deleted. This means there will be 
# about 2-6 weeks of backups at any given time.

# Creates a lock so that only one instance of this script may be executed
[ "${FLOCKER}" != "$0" ] && exec env FLOCKER="$0" flock -xn "$0" "$0" "$@" || :

print_help () {
    printf "Performs an incremental backup (if possible) on the given VMs.\n\n"
    printf "Usage:\n  -v [VM_NAMES]\n  -o [PATH]\n\n"
    printf "Example: vm-snapshot -v vm1,vm2,vm3 -o /tmp/backups\n"
}

BACKUP_DIR=""

while getopts ':v:o:h' OPTION; do
    case "$OPTION" in    
        v)
            IFS=',' read -r -a VMs <<< "$OPTARG"
        ;;
        o) 
            BACKUP_DIR=$OPTARG
        ;;
	h)
            print_help

	    exit 0
	;;
        \?)
            printf "Invalid usage: \n\n-v [VM_NAMES] \n\n-o [PATH]\n\n"
	    printf "Example: vm-snapshot -v vm1,vm2,vm3 -o /tmp/backups"
        ;;
    esac
done

shift "$(($OPTIND -1))"

if [ ${#VMs[@]} -eq 0 ] || [ ! -d $BACKUP_DIR  ]; then
    printf "Please supply at least one VM name and an output dir "
    printf "(vm-snapshot -v vm1 -o /tmp/backups).\n\n"
    printf "Multiple VMs may be passed with commas (-v vm1,vm2,etc...).\n"

    exit 1
fi

BACKUP_TOOL=`which virtnbdbackup`

if [ -z "${BACKUP_TOOL}" ]; then
    printf "Could not find virtnbdbackup.\n\n"
    printf "https://github.com/abbbi/virtnbdbackup\n"

    exit 2 
fi

DAY_OF_MONTH=`date +'%d'`

SNAPSHOT_NAME=`date +'%Y-%m'`

# Backup all the VMs, running or stopped, incrementally if possible
for name in ${VMs[@]}; do
    SNAPSHOT_PATH=${BACKUP_DIR}/${name}/${SNAPSHOT_NAME}

    printf "Backing up ${name} to ${SNAPSHOT_PATH}\n"
   
    START_VM=""

    if [ ! -d ${SNAPSHOT_PATH}  ]; then
        START_VM=" -S"
    fi

    ${BACKUP_TOOL}${START_VM} --noprogress -d ${name} -l auto -o ${SNAPSHOT_PATH}

    # Delete last month's backups if our latest backup succeeded and it is the
    # middle of the current month.
    if [ $? -eq 0 ] && [ $DAY_OF_MONTH -eq 15 ]; then
        LAST_MONTH=`date -d "$(date +%Y-%m-1) -1 month" +%Y-%m`
    
    	LAST_MONTHS_BACKUPS_DIR=${BACKUP_DIR}/${name}/${LAST_MONTH}

        if [ -d ${LAST_MONTHS_BACKUPS_DIR} ]; then
            printf "Removing backups for ${name} for ${LAST_MONTH}"
	
            rm -rf ${LAST_MONTHS_BACKUPS_DIR}
        fi
    fi
done

exit 0

Some general notes;

• Only one instance of this script will run at a time
• Multiple VMs may be specified
• Starts the VM and performs a full snapshot if required
  • Performs an incremental backup, otherwise
• Provides a flexible timeframe of snapshots (2-6 weeks, depending on where you are on the calendar)
• Deletes last months snapshots (if any) on the 15th of the current month

Sample usage;

./vm-snapshot.sh -v vm1,vm2 -o /tmp/backups

I hope this is helpful to someone out there.

Cheers!

[abbbi]

hi,

thanks! I did some minor modifications (shellcheck related, dont stop if one backup of a VM fails but exit with failure, etc) and added this within the scripts directory:

https://github.com/abbbi/virtnbdbackup/blob/master/scripts/vmbackup.sh

[sentry0]

Cool. I did some mods of my own.

1. I added virsh into the mix to check the domstate of the VM before attempting to operate on it
2. You have to explicitly turn on the pruning of old snapshots with -p flag
3. You can specify "*" (with double-quotes) to select all VMs on the system
4. Other misc. changes to simplify/streamline the script

I have it in a repo here - https://github.com/slackdaystudio/vm-snapshot

I have been running this script for a bit now. It seems pretty solid in my tests.