Use Case: Recover from Transfer Failure

Scenario

A field technician’s pack operation is interrupted mid-way — the USB drive runs out of space, or the process is killed by a power loss. The tool’s state management and resume capability allow the operator to recover without starting over.

Use Case: Recover from Transfer Failure UC-TRANSFER-006

status: approved tags: transfer, error-recovery, resume, state release: v1.0 specifies: FR-TRANSFER-024, FR-TRANSFER-025, FR-TRANSFER-027, FR-TRANSFER-035, FR-TRANSFER-036, FR-TRANSFER-037

Recover from an interrupted pack or unpack operation using manifest-based state tracking and the --resume flag. Failure: Operation interrupted by insufficient USB space, power loss, or user abort. Diagnose: Tool provides clear error message explaining what went wrong and how to recover. Resume: User runs the same command with --resume. The tool reads the manifest, identifies the last completed chunk, and continues from there. Acceptance Criteria: Transfer completes successfully after recovery with no data loss or corruption.

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Prerequisites

• Prior operation: A pack or unpack that was interrupted mid-operation

• Manifest: airgap-transfer-manifest.json written before the failure (contains chunk completion state)

• Transfer media: USB drive(s) with partial transfer data

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Workflow Steps

Scenario A: Pack Interrupted by Insufficient Space

1. Pack starts normally

airgap-transfer pack ~/large-dataset/ /media/usb-drive

The tool begins writing chunk_000.tar. Midway through chunk_001.tar, the USB runs out of space.

2. Tool reports clear error

error: insufficient space on /media/usb-drive (1.2 GB available, 8 GB needed for chunk_001)
Hint: Free space or insert a larger USB, then run with --resume

The manifest records chunk_000 as completed and chunk_001 as in-progress.

3. Operator swaps USB and resumes

# Insert fresh USB drive
airgap-transfer pack ~/large-dataset/ /media/usb-drive --resume

The tool reads the manifest, sees chunk_000 is complete, and resumes from chunk_001.

4. Pack completes

Resuming from chunk 1 (1 of 4 already complete)
...
Pack complete. 4 chunks created, all verified.

Scenario B: Unpack Interrupted by Power Loss

1. Unpack starts on air-gapped machine

airgap-transfer unpack /media/usb-drive ~/restored/

The tool extracts chunk_000.tar and chunk_001.tar successfully. Power is lost during chunk_002.tar.

2. After power restoration, check state

airgap-transfer list /media/usb-drive

Shows chunks 0 and 1 as completed, chunk 2 as in-progress.

3. Resume unpack

airgap-transfer unpack /media/usb-drive ~/restored/ --resume

The tool re-extracts chunk_002.tar from the beginning (partial extraction is discarded) and continues through the remaining chunks.

Scenario C: Missing Chunks During Unpack

1. Unpack with incomplete USB set

airgap-transfer unpack /media/usb-drive ~/restored/

error: chunk_002.tar not found at /media/usb-drive/chunk_002.tar
Hint: Connect the USB containing chunk_002, then run with --resume

2. Connect correct USB and resume

# Mount USB containing chunk_002
airgap-transfer unpack /media/usb-drive ~/restored/ --resume

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Acceptance Criteria

• Interrupted operations resume from the last completed chunk, not from scratch

• Clear error messages explain what failed and how to recover

• No data loss or corruption after recovery

• Manifest accurately tracks chunk completion state across interruptions

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Error Scenarios

Error	Cause	Recovery
“Insufficient space”	USB full during pack	Swap USB, --resume
“chunk_002 not found”	Missing USB during unpack	Connect correct USB, --resume
“Manifest incompatible”	Resume with different arguments	Use --force to start fresh
“All chunks already complete”	Resume on finished transfer	Nothing to do — already done

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Related Documents

• Large File Transfer — Standard pack/unpack workflow

• Multi-USB Transfer — Multi-drive coordination with resume

Linked Requirements

ID	Title	Status	Release	Verified By
FR-TRANSFER-024	Maintain Operation State	approved	v1.0	TC-STA-001
FR-TRANSFER-025	Track Chunk Completion	approved	v1.0	TC-STA-002
FR-TRANSFER-027	Resume Interrupted Unpack	approved	v1.0	TC-STA-004
FR-TRANSFER-035	Detect Insufficient USB Capacity	approved	v1.0	TC-TRANSFER-ERR-001
FR-TRANSFER-036	Handle Missing Chunks	approved	v1.0	TC-TRANSFER-ERR-002
FR-TRANSFER-037	Clear Error Messages	approved	v1.0	TC-TRANSFER-ERR-003

Traceability

Tests

Integration Tests

No needs passed the filters

Unit Tests of Linked Requirements

ID	Title	Status	Tests
TC-STA-001	Persist Operation State	approved
TC-STA-002	Track Chunk Completion	approved
TC-STA-004	Resume Interrupted Unpack	approved
TC-TRANSFER-ERR-001	Insufficient USB Capacity Error	approved
TC-TRANSFER-ERR-002	Missing Chunks Error	approved
TC-TRANSFER-ERR-003	Clear Error Messages	approved