BTRFS: Automatic Snapshots Script

btrfsSnapshot.sh

#!/bin/bash
set -e

# ebal, Mon, 07 Nov 2022 08:49:37 +0200

## 0 0 * * Fri /usr/local/bin/btrfsSnapshot.sh

# paths MUST end with '/'
btrfs_paths=("/" "/home/" "/opt/")
timestamp=$(date +%Y%m%d_%H%M%S)
keep_snapshots=3
yymmdd="$(date +%Y/%m/%d)"
logfile="/var/log/btrfsSnapshot/${yymmdd}/btrfsSnapshot.log"

sudo mkdir -p "/var/log/btrfsSnapshot/${yymmdd}/"

echo "######## $(date -R) ########" | sudo tee -a "${logfile}"
echo "" | sudo tee -a "${logfile}"

for btrfs_path in "${btrfs_paths[@]}"; do

    ## Create Snapshot directory
    sudo mkdir -p "${btrfs_path}".Snapshot/

    ## How many Snapshots are there ?
    list_btrfs_snap=$(sudo btrfs subvolume list -o -r -s "${btrfs_path}" | grep -c ".Snapshot/")

    ## Get oldest rootfs btrfs snapshot
    while [ "${keep_snapshots}" -le "${list_btrfs_snap}" ]
    do
        prev_btrfs_snap=$(sudo btrfs subvolume list -o -r -s  "${btrfs_path}" | grep ".Snapshot/" | sort | head -1 | awk '{print $2}')

        ## Delete a btrfs snapshot by their subvolume id
        sudo btrfs subvolume delete --subvolid "${prev_btrfs_snap}" "${btrfs_path}" | sudo tee -a "${logfile}"

        list_btrfs_snap=$(sudo btrfs subvolume list -o -r -s "${btrfs_path}" | grep -c ".Snapshot/")
    done

    ## Create a new read-only btrfs snapshot
    sudo btrfs subvolume snapshot -r "${btrfs_path}" "${btrfs_path}.Snapshot/${timestamp}" | sudo tee -a "${logfile}"

    echo "" | sudo tee -a "${logfile}"

done