Backing up with Proton Drive CLI

A script to automate my backup to Proton Drive

The Proton Drive CLI is finally available! I received the official Proton e-mail on October \(1^{st}\). I immediately downloaded it and started to play a bit with it. Since I switched from a macOS to a Linux system I had been wondering how to efficiently do my backups on the Proton provided drive service.

I first had to struggle a little because I wasn’t sure how to efficiently upload many GB of data. One possibility was to create an archive of all the filese I wanted/needed to backup and then upload it. One advantage of such approach is that you can have a cheksum file to help verify that all files are properly uploaded. One downside is that you loose the tree-like structure of your files and folders and you need to download the entire archive even if you need access to only a handfull of files. I finally decided to use an approach that would allow to maintain the structure of my Documents folder (the one I needed backup).

With the help of Lumo AI I created a script (see below) that allows such task while also writing a .log file to keep track of everything that goes wrong. I have also implemented the –folder-conflict-strategy and –file-conflict-strategy to merge or skip folder of files that already exists and that haven’t changed since the last backup!

#!/usr/bin/env bash
set -euo pipefail

DATE=$(date +%Y-%m-%d)
LOG="$HOME/.XXXX/YYYYY/home-backup.log"
REMOTE_PARENT="/my-files"
REMOTE_FOLDER="documents_backup_${DATE}"
REMOTE_PATH="${REMOTE_PARENT}/${REMOTE_FOLDER}"
KEEP=4
DRY_RUN=1

log() { echo "$(date '+%F %T') $*" >> "$LOG"; }

log "=== documents backup started ==="

# ---- Create destination folder ----
if proton-drive filesystem create-folder "$REMOTE_PARENT" "$REMOTE_FOLDER" --json >> "$LOG" 2>&1; then
    log "Created remote folder: $REMOTE_PATH"
else
    log "Note: Folder creation skipped (may already exist)"
fi

# ---- Upload Documents ----
proton-drive filesystem upload \
    /home/XXXXX/Documents "$REMOTE_PATH" \
    --folder-conflict-strategy merge \
    --file-conflict-strategy skip \
    --skip-thumbnails \
    --json >> "$LOG" 2>&1 \
    || { log "ERROR: upload failed"; exit 1; }

# ---- Retention: prune old dated backups ----
log "Processing retention policy"
LISTING=$(proton-drive filesystem list "$REMOTE_PARENT" --json) \
    || { log "ERROR: listing failed, skipping prune"; exit 0; }

BACKUPS=$(echo "$LISTING" | jq -r '.[].name // empty' \
    | grep -E '^documents_backup_[0-9]{4}-[0-9]{2}-[0-9]{2}$' \
    | sort)

COUNT=$(echo "$BACKUPS" | wc -l)
log "found $COUNT matching backup folders"

if (( COUNT <= KEEP )); then
    log "nothing to prune"
    exit 0
fi

TO_DELETE=$(echo "$BACKUPS" | head -n -$KEEP)

echo "$TO_DELETE" | while read -r folder; do
    [[ -z "$folder" ]] && continue
    FULL_PATH="${REMOTE_PARENT}/${folder}"
    if (( DRY_RUN )); then
        log "DRY-RUN: would delete $FULL_PATH"
    else
        log "deleting $FULL_PATH"
        proton-drive filesystem delete "$FULL_PATH" >> "$LOG" 2>&1 \
            || log "WARN: failed to delete $FULL_PATH"
    fi
done

log "=== backup finished ==="