Termux USB Pendrive Multi-Part Backup System & Syncthing Sync

Automated, robust, and encrypted USB pendrive backup system designed for Android (Termux) with multi-part chunking (~500MB per file), self-healing Syncthing synchronization, and cross-platform restoration.

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⚡ 1-Command Quick Setup (Termux)

On your Android phone in Termux, run this single command to download and set up everything automatically:

pkg upgrade -y && pkg install curl -y && bash -c "$(curl -fsSL https://raw.githubusercontent.com/mahdi4261/backup-script/main/setup-backup.sh)"

(Alternatively, via Git clone:)

pkg upgrade -y && pkg install git -y && git clone https://github.com/mahdi4261/backup-script.git ~/backup-script && bash ~/backup-script/setup-backup.sh

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✨ Features

• Dedicated Folders per Drive: Each pendrive is backed up into its own folder: ~/storage/shared/.backups/<UUID>/.
• ~500MB Multi-Part Splitting: Archives are chunked into 500MB parts (part-001, part-002, ...), overcoming the 4GB FAT32 Android file limit.
• In-Memory Streaming: Zero multi-gigabyte temporary files on disk; compression, encryption, and splitting stream directly through memory pipelines.
• Hybrid RSA + AES Encryption (Optional): Secures pendrive data using public-key hybrid encryption before storing or syncing.
• Syncthing Integration:
  • Automatically installs and starts Syncthing in the background (--no-browser).
  • Per-Part Incremental Syncing: Triggers sync after each 500MB part completes (and instantly for key.enc), so files transfer over the network while subsequent parts are still being processed.
  • Watchdog in backup.sh ensures Syncthing stays running.
• Android CPU Wake Lock: Holds termux-wake-lock to keep backups and Syncthing alive when the screen is locked.
• Safe Atomic Operations: Parts are streamed to temporary chunks (part-*.tmp) ignored by Syncthing until fully written, with automatic recovery if an interrupted backup is detected.
• Cross-Platform Restore Utility: Includes restore.sh to decrypt and extract backup parts back into original directory structures.

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📂 Repository Contents

File	Description
setup-backup.sh	Automated 1-step installer for dependencies, permissions, Syncthing, and scripts
backup.sh	Main scanner and backup engine (detects pendrives, compresses, splits, encrypts)
restore.sh	Restore & extraction utility (works on Android Termux, Linux, macOS, and WSL)
backup_public_key.pem	Public key certificate used for encrypting backups
run_tests.sh	Automated local test suite verifying multi-part backups, restore, and rotation

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🚀 Usage

1. Manual Backup Run

Plug in your USB pendrive via OTG and run:

bash ~/backup.sh

2. Automatic Scheduled Backups (Cron)

The setup script automatically registers the backup job and starts the crond daemon to scan every 1 minute in the background.

To inspect or edit your scheduled cron schedule:

crontab -l

(The configured entry runs every 1 minute: * * * * * ... ~/backup.sh)

3. Restoring Files with restore.sh

To extract original files from a backup folder:

# For unencrypted backups:
./restore.sh ~/storage/shared/.backups/<UUID> [destination_folder]

# For encrypted backups (with your private key):
./restore.sh ~/storage/shared/.backups/<UUID> ~/backup_private_key.pem [destination_folder]

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🔄 Syncthing Pairing Guide

1. Open your phone's browser to http://127.0.0.1:8384.
2. Click Actions $\to$ Show ID to view your phone's Syncthing Device ID.
3. On your remote PC / Server, install Syncthing and click Add Remote Device, then paste your phone's Device ID.
4. On your phone, add folder ~/storage/shared/.backups (or /storage/emulated/0/.backups), check the box for your remote PC under Sharing, and set Folder Type to Send Only.
5. Accept the folder on your PC as Receive Only to automatically mirror all pendrive backups!

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🔒 Security Best Practices

Important

Keep your backup_private_key.pem safe and never commit it to public repositories. Only the public key (backup_public_key.pem) is stored on the phone to encrypt data.