DeepSpeed SIGBUS Exit Code -7 After Checkpoint Load
DeepSpeed training crashes with SIGBUS (exit code -7) after loading a checkpoint, with no Python traceback. This typically indicates a memory-mapped file access failure. The checkpoint file was truncated, deleted, or on a filesystem that was unmounted. Denpex detects the SIGBUS pattern and correlates it with checkpoint file integrity.
DeepSpeed training crashes with SIGBUS (exit code -7) after loading a checkpoint, with no Python traceback.
What this failure is
DeepSpeed SIGBUS Exit Code -7 After Checkpoint Load is a Data Integrity failure seen during ML training runs. DeepSpeed training crashes with SIGBUS (exit code -7) after loading a checkpoint, with no Python traceback. This typically indicates a memory-mapped file access failure. The checkpoint file was truncated, deleted, or on a filesystem that was unmounted. Denpex detects the SIGBUS pattern and correlates it with checkpoint file integrity. Common tags: Deepspeed, Sigbus, Exit Code 7, Checkpoint.
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Why it happens (the mechanism)
A memory-mapped checkpoint file was truncated or deleted while the process still had it mapped, causing SIGBUS when the process tries to read the missing pages. NFS mount became stale or was unmounted between checkpoint save and load, making the mapped file inaccessible. DeepSpeed's NVMe offload uses mmap for checkpoint buffers, and the underlying file was deleted or moved. Disk corruption or filesystem journaling errors made the checkpoint file partially inaccessible. Taken together, these mechanisms explain why the failure is reproducible, why it tends to surface on specific workloads or scales, and why generic mitigation attempts often fall short without addressing the underlying cause.
What you'll observe
- Training crashes with exit code -7 (SIGBUS) immediately after loading a checkpoint
- No Python traceback is produced. The process dies at the OS level
- All ranks crash simultaneously, suggesting a shared checkpoint file issue
Common symptoms and what they mean
| Symptom | Why it happens |
|---|---|
| Process exits with code -7 (SIGBUS) or signal 7 | A memory-mapped checkpoint file was truncated or deleted while the process still had it mapped, causing SIGBUS when the process tries to read the missing pages |
| No Python traceback or error message. Just an abrupt exit | NFS mount became stale or was unmounted between checkpoint save and load, making the mapped file inaccessible |
| dmesg shows SIGBUS or Bus error on the training process | DeepSpeed's NVMe offload uses mmap for checkpoint buffers, and the underlying file was deleted or moved |
| The crash occurs immediately after torch.load() or DeepSpeed checkpoint load | Disk corruption or filesystem journaling errors made the checkpoint file partially inaccessible |
| NFS mount points show as stale or unmounted in df output | A memory-mapped checkpoint file was truncated or deleted while the process still had it mapped, causing SIGBUS when the process tries to read the missing pages |
Which systems are affected
- Training with memory-mapped checkpoint files on NFS
- DeepSpeed with NVMe offload checkpointing
- Shared filesystem environments (NFS, Lustre, Ceph)
- Long-running training jobs with periodic checkpoint loads
How to confirm this is the problem
Use this checklist to test the hypothesis against a small reproduction. No single line proves the root cause, so preserve the preceding events and compare one variable at a time.
- ✓Reproduce the failure from a clean checkpoint/seed: the symptom must appear without warm-up state from a previous run.
- ✓Verified signal present: Process exits with code -7 (SIGBUS) or signal 7
- ✓Verified signal present: No Python traceback or error message. Just an abrupt exit
- ✓Verified signal present: dmesg shows SIGBUS or Bus error on the training process
- ✓Verified signal present: The crash occurs immediately after torch.load() or DeepSpeed checkpoint load
- ✓Verified signal present: NFS mount points show as stale or unmounted in df output
- ✓A targeted fix from the "How to fix it" section eliminates or substantially reduces the symptom within one validation pass.
The fix and the prevention pattern
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Diagnose this failure in VS Code
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DeepSpeed changes when parameters, gradients and optimizer state are created, partitioned, gathered and offloaded. The hub separates ZeRO, memory, checkpoint and pipeline failures by lifecycle phase.
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Root cause
- A memory-mapped checkpoint file was truncated or deleted while the process still had it mapped, causing SIGBUS when the process tries to read the missing pages
- NFS mount became stale or was unmounted between checkpoint save and load, making the mapped file inaccessible
- DeepSpeed's NVMe offload uses mmap for checkpoint buffers, and the underlying file was deleted or moved
- Disk corruption or filesystem journaling errors made the checkpoint file partially inaccessible
The fix and how to prevent it
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